: 01 Seville runs rough, 0306 code intermittent



01slsseville
01-12-14, 01:40 AM
tomorrow i'll switch injectors (checked with stethoscope, all clicking normally / alike) and do a compression test. after going blind reading through millions of posts and threads, i've seen comment that only a leak down will do for this engine, a standard compression test can't be done (?)

high praise and kudos to the likes of ranger, sub, and the rest of the assorted gods that grace this place. (and noobs and twits like me, that allow you a place to show off all that einsteian knowledge! )

i'm dreading a burnt valve; and to wit, is it possible to "do the front head in the car" ( I have a bunch of wrenches, but that's past what I'd prefer to tackle.) I'm assuming / hoping a compression test will tell if it's the valve? (already swapped coils, 0306 persists )

engine runs bad even before the code sets. no other codes (at the moment) i've already replaced the "outer / big" plenum from being ripped in the usual spot, and "leak checked" the vac lines a million times with ether / maf cleaner, etc. I'm assuming the pcm's are good, since they swapped with the coils. fresh AC plugs (and btw, of course the #5 plug snapped off. luckily, and equally rarely in my experience, the plug sheared cleanly off just above the hex / body and took the electrode and insulator clean out with it. after re booting my heart, i was able to take it out with a screw extractor, between beers.

hope i can be as lucky with the six problem.

TIA for all your help, been reading these threads for years now, on my second SLS.

Submariner409
01-12-14, 09:01 AM
PITA, but swap the coil cassettes side for side: They're identical except for color and the ICM in each cassette L-leg is identical also. If the miss moves, the cassette has a bad coil (1 of 4 potted coils in each cassette). While you're in there, check the spark plug/coil connector boots for carbon tracking - thin black sparky-looking tracks inside the rubber boot and on the plug insulator. Guaranteed miss. AC Delco #41-987 Platinum plugs. Bad/burned valves in a Northstar are rare.

The crankshaft rotation sensors - 2 CKPs and a CMP - feed the PCM which in turn sends ignition trigger signals to the ICM in each coil cassette. (The Acronyms sticky post ^^^)

I'll stick my neck out and say it's either an injector, injector wiring, or faulty ignition coil/boot/plug.

Ranger
01-12-14, 11:46 AM
:welcome:

I seriously doubt you have a burnt valve. It would be the first that I have heard of.


I'm assuming the pcm's are good, since they swapped with the coils.
I think you meant ICM's.

I assume you have cleaned the TB?


i've seen comment that only a leak down will do for this engine, a standard compression test can't be done (?)
I think that was in reference to checking for a HG leak. For your purposes a compression test CAN be done, but usually isn't necessary.

Mark D
01-13-14, 10:03 PM
After I got a 2000 ETC as a repairable wreck, I learned about those coil cassettes. The car had a P0306 (why is it always # 6?)
I decided to check spark first. How to do that?
Rather than switch coils, I removed the left cassette and attached plug wires to each plug connector. I connected these plug wires to spark plugs and cranked the engine over. Three of the four plugs fired. #6 did not.
I priced a new one, and then went to a salvage yard and got a used one. It works fine, but looks a bit skanky. They got it from the bottom of a 55 gallon drum full of various types of ignition modules.

Also check compression! I recently had the #6 hole on my wife's '98 STS go dead. I checked spark, and that was fine.
I decided to check compression.
This car has only about 5000 miles since the heads were completely rebuilt during a head gasket job where I installed Jakes studs. I would never, ever, do a head gasket job again without his studs!!!!

Anyway, zero compression. Zero! Not even a pound of pressure.
Can't be rings, there would at least be 25 or something.
Must be a stuck valve.
That was confirmed when I backed it out of my shop to make room for something else and suddenly it was running fine again. This, after her driving it a couple hundred miles on 7 cylinders. (SES light flashing all the while) Converter seems ok yet.
So, I dosed it up with a whole bunch of Sea Foam in both the oil and the gas. I think it's going to be ok, but time will tell.

BTW, at 210K miles, those valves were all used up. They're so thin that grinding them isn't advisable, in my view.

If it isn't one of the above on your car, there isn't much else it can be other a plugged injector.
If the cylinder is stone dead, and the injector is working, your plug in that cylinder should be pretty wet with gas.
Mark D.

01slsseville
02-02-14, 01:36 AM
Thanks much for the replies, all. Here's what I've done so far. After getting an 0306 from my toy obd 2 readery (auto xray, I know...) I swapped injectors w/ cyl. 4, code followed, so replaced the injector with a "decent" used fj 428 (actually two, since the "pintle cap" as it were on these was bad on the first one.) Since then, replaced the fuel rail after losing an injector tab (brand new fuel rail.) "new" 0304 code persists like a m'fer. Bad idle (loping at very best) cleaned everything under the sun w/ electronic cleaner. tested voltage at injector plug, 11-11.9 ish while running, at rest same as sister plugs, 9ish. swapped injector plugs from 2 to 4, no change, still 0304. mil went from only displaying code (and flashing mil) under load (lots of handy steep hills) to now instantly setting code, still 04, and yet will "go intermittent" as far as display, still runs bad all the time. less so at speed, terrible under any load.

sprayed the world with various flammables to test for vac leaks, endlessly, esp. plenum boot. checked endlessly all wiring, pcm loom, etc.

i'm going mad, mad, i tell you. (insert looney laugh here, but it sure ain't funny.) ran "cataclean" through previously, top tier gas, et al.

i know my trans solenoid is bad (0741) and will crack the case and fish it out at some point if this issue proves curable. car has 166k on it, not worth tons of money (still love the car.)

THANK YOU for your assistance, all.

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p.s, swapped coils (see first post/plea for help) checked (with a magnifying glass) coil plugs, wiggle tested wiring, et al. that the code started as an 06, then moved with initial injector swap and now seems firmly rooted in 04 kills me. moved all injectors all around when replacing fuel rail, all new o rings, lubed. managed to pull the egr / vac tube from the blow off valve and haven't gotten that back in, it's cracked a little anyway. assuming with the blow off valve closed, no "harm" to engine management since it must only pull pressure from the manifold when it's inserted and holding the valve open, if it was sucking or pushing that much air when running, it'd affect all cylinders equally. looks like i'll be replacing the intake gaskets and small plenum boot before too long just because, so i'll replace that egr line nipple then.

Ranger
02-02-14, 11:34 AM
i know my trans solenoid is bad (0741) and will crack the case and fish it out at some point if this issue proves curable.
Before you waste your time, P0741 alone has nothing to do with the TCC solenoid. THAT is a leaky TC seal. P1860 is the solenoid which also sets P0741 as a result of the failed solenoid.
http://www.cadillacforums.com/forums/northstar-engines-system-technical-discussion/149834-information-p0741-p1860-1998-a.html

01slsseville
02-02-14, 03:36 PM
well, thanks for that info. not only spared the grief of cracking the trans without shop gear and nine factory techs, but essentially it does put an expiration date on the car. the mil light on isn't a killer, nor is the non functionality of the tcc, since i basically only drive the car to work, etc, and it's not a lengthy drive, so if i can fix the 0304, i'll drive it till it, or i, drop (in either case, a flatbed tow to the nearest ditch will be sufficient, i'm just more biodegrable than the seville!)

this is one of those issues that "feels" like it's gotta be some simple dumb thing that is staring me right in the face, but i've been at wits end with it for a while now, as have many others (from reading through the threads. funny how we can find things incredibly interesting even when we "don't have that problem per se, eh?)

thanks again for the forum.

being a 6volt guy in a 12volt world, i'll probably go back to carbs and points, et al when this old girl passes. my "other" ride is a 1956 panhead, so the whole monkeys-with-shotguns descriptor may apply... but then, when did commuter vehicles require Seawolf technology? what, did i miss the "vaporize traffic" button on the console somewhere?

: )

01slsseville
02-02-14, 07:15 PM
p.s., yes, i sterilized / sterilize the tb from time to time, like an oil change. same w/ iac, tps, egr , etc. all vac lines, connections, rubber stuff and plastic stuff. it is an oven i there, and everything gets baked to a crisp, so it's a constant. plus it is getting to be high miles, so heat attrtion s heavy.

today i swapped coils, again, no effect, swapped plugs and boots, checked all vac lines and measured voltage at the injector connection engine off / key on and running, 12 volts at connector, still 0304. bad idle and rough climb to high rev, very intermittent code display.

Ranger
02-02-14, 08:52 PM
well, thanks for that info. not only spared the grief of cracking the trans without shop gear and nine factory techs, but essentially it does put an expiration date on the car. the mil light on isn't a killer, nor is the non functionality of the tcc, since i basically only drive the car to work, etc

You can drive the car with the P0741 forever. It'll just eventually lower your MPG by a mile or two as it gets worse. The bad news is you will not pass an emissions test if you are subject to one (Thankfully I'm not).

If swapping coils, plugs and boots did not move the misfire, the only thing left is an injector. Use a stethoscope to see if #4 has the same rhythmic pulsing as the others do.

EDIT:
Wait a minute, your title says #6 misfire. Now you said #4.

01slsseville
02-02-14, 10:55 PM
a, yes i'm nine shades od green with envy because not only do you not have to play c.a.r.b. / scaqmd wargames, but by definition you also get to laugh uproariously at those of us who have to put up with jerry the moonbeam brown.... : ) and b, that is exactly what is increasing my beer intake; what started out as a 306 moved to cylinder 4 on the first injector swap, following the errant injector, one would suppose. but after replacing that injector with first a used one, then a new one, replete with all new o rings, the 04 persists. all kinds of sideways adventures later, i still have the 04, though semi driveable now ( with no apparent reason).

swapped coils twice, moved injectors repeatedly and all over, have good fuel pressure (notthat ,hat wouldn't affect all cylinders) have 12 volts at all injectors, swapped plugs (new, delco, plats) and boots, re sprung coil / plug springs, no carbon tracking, even swapped injector plugs, still 04. wtf happened to 06, anything is possible and elvis could be pumping gas in idaho, but seems unlikely the pcm would croak right in time to make a 04 the "new" problem, right? what else to test without dropping condo payments to some shop with a scope and a hundredth of your experience and knowledge?

drewsdeville
02-02-14, 11:04 PM
today i swapped coils, again, no effect, swapped plugs and boots, checked all vac lines and measured voltage at the injector connection engine off / key on and running, 12 volts at connector, still 0304. bad idle and rough climb to high rev, very intermittent code display.

The injector harness will always have voltage, most likely supplied from an underhood fuse box. The injectors are ground switched on the opposite side by a set of transistors in the PCM, which can be destroyed by bad injectors. If you want to test the circuit, you'll need to verify a voltage drop occurring when the ground is switched. You'd need a scope to do this.

That said, only worry about this if you can't hear the injector clicking. If it clicks, it works.

01slsseville
02-02-14, 11:49 PM
thanks, did that (checked with a stethoscope) first round out. did that even before swapping coils, even though all injectors were clicking (some "differently" than others, which they still do, figure it's an individual wear pattern that gives each its own sound; so i figure the pattern and volume are indicators of performing correctly.) even though number four and six at that time made "the right noise", my scanner told me 0306. when i moved the coils, the code remained, when i swapped injectors between 6 and 4, the code followed.

now, no matter what, the code stays at 4.

the fuses are all good in the underhood box, guess i need to check under the seat though (?)

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p.s., excuse the bad spelling, thank you internet-on-the-cell-phone. : /

98eldo32v
02-03-14, 01:24 AM
"That said, only worry about this if you can't hear the injector clicking. If it clicks, it works".

An injector can be functioning BUT not passing enough fuel...... if an injector isn't passing enough fuel, that can induce a misfire.

Where did you get the used injector from? Was it from a recently running vehicle? When you reinstalled the injectors, did you make sure to lube the lower o ring that seats back into the manifold?

I would go back to the injector in question and scrutinize that injector/cylinder some more.....

Ranger
02-03-14, 10:15 AM
even though number four and six at that time made "the right noise", my scanner told me 0306. when i moved the coils, the code remained, when i swapped injectors between 6 and 4, the code followed.

now, no matter what, the code stays at 4.
Have you considered a bad ICM?

Submariner409
02-03-14, 11:48 AM
Have you considered a bad ICM?

Thought about that - trouble is, there's an ICM in each cassette L-leg - he swapped cassettes and the fault remained at #4.

ICM multi-pin connector on the left (front) bank ?

Ranger
02-03-14, 03:01 PM
Ahh, I forgot that, but in post #1 he said "already swapped coils, 0306 persists". The fact that it moved from #6 to #4 is perplexing.

drewsdeville
02-03-14, 04:16 PM
"That said, only worry about this if you can't hear the injector clicking. If it clicks, it works".

An injector can be functioning BUT not passing enough fuel...... if an injector isn't passing enough fuel, that can induce a misfire.


Let me clarify - if the injector is clicking, THE CIRCUIT works.

01slsseville
02-03-14, 11:07 PM
I visually checked the connector (both, front and rear) and saw no obvious damage, corrosion, bent gidgets, whatever. i get that the injector harness is given 12 v constantly, and the pcm grounds each station to fire; how to correctly check that with an plain jane digital volt meter? i just inserted million gauge wires into the pin slots on the injector connectors and read the voltage static (key on) and running to assess voltage delivery.

ironically enough (insert louis black voice here) my mileage has climbed back up to (insert black's spastic finger here) 18.9 , even though the engine idles at a stoplight like miley cyrus at the vma's.

drove both to work (20 miles one way) and to the doc's and back today, total about 100 miles; engine ran like crap and overheated "a little" on hills, but threw NO code on the dash scan, but did on the reader. gave me a 0101 on the way to work, a 0410 p.m. and a steady 0304 later. 0101 and 0410 disappeared, and don't even show in history.

engine NEVER runs smooth, at first when dealing with this before it finally threw a code, i was convinced the cat was plugging up, runs that lumpy.

98eldo32v
02-04-14, 10:11 PM
Let me clarify - if the injector is clicking, THE CIRCUIT works.


Trying swapping in another injector into cylinder #4.......

01slsseville
02-04-14, 10:58 PM
so, in the Bataan death march that we like to call traffic here, over a twenty mile stretch at like, .45 mph pretty much the whole way, the temp rose to it's "hillclimbing" mode of just one notch over 12:00, then eventually settled back down. now, I realize my coolant level is a tad high, i'm not running it at dead level to the clear-to-black plastic shading of the recovery tank, thanks to the paranoia brought on by slowly losing the recovery tank to the usual crack-on-the-bottom-that-makes-you-do-the-i'm-losing-my-headbolts danse macabre, but THIS episode provided not only the usual 0741 and 0304, but also a 0171 and an 0174.

well, then, as gilda or carvey's church lady would say.

is it not then in the realm of possibility (and yes, it makes ZERO sense, given the initial 0306... ) that the fuel trims may indicate some danged small plenum rip / tiny tear, or some wild cosmically induced (i must have been REALLY bad in a previous life... stalin's cousin or something...) leakage in the intake manifold gasket for 4? w.the.h. now, that'd even make more sense IF the intake gaskets weren't danged individuals, or the temp didn't rise both "cruising" (yeah, that's what we're calling it this week in So Cal...) or "climbing", both scenario's which route back around to being contradictory in flow chart land.

tonight the wretched carcass of a once proud deville donated all the sensor connectors EXCEPT the maf (naturally which i'm most in need of, the poor wires going to that are battle-flag-of-the-republic and have to be massaged to not induce a high idle occasionally. but i am planning on replacing ALL the injector connectors and the tps and maf at this point, (only because the maf deserves it and the dang retaining clip died on the tps connector; most of the plastic stuff is so heat baked it will crumble in my hands like dust in the wind. yay.) i also have another full set of injectors coming (used, ebay, i don't expect to use them all, will cherry pick if at all for the non problem child cylinders, and recall there is a brand new fj-428 in $, er, 4, or there was up until the fuel rail changeout after an injector clip / tab loss ( $? 4? coincidence? you decide...)

i'll also do the intake gaskets and small plenum, at this rate, why not. i also harvested some small hard plastic air lines and better-shape-than-mine pcv lines from the deville, so that stuff will update (like a bad hard drive reboot, for crying out loud.)

IF there is a positive end to this journey, at least may it serve some future attendee of this forum well, and possibly save them some grief. Thanks again to the hosts for that. Apologies again for the long winded nonsense, but as you are aware, the holders of both Northstar and Caddy-in-general-actual-knowledge is exeedingly rare, INCLUDING longstanding dealers. they are just a business, this place is hallowed ground.

Thanks,all.

98eldo32v
02-05-14, 03:25 AM
This is a battle, but you shall win the war........

Submariner409
02-05-14, 08:48 AM
What's wrong with a temp gauge indication of one tick past 12 o'clock ????

Put this in your computer car file ....................

For any of these Northstar models with a temp "gauge", the 9 tick marks indicate the same approximate temperatures. The 12 o'clock mark is heavily damped - if the needle never moved from 12 o'clock the temp would be somewhere between 190 and 205 degrees.

"OMG, Betsy - The gauge in the car moved today. We're in deep trouble !"

Ranger
02-05-14, 10:41 AM
but THIS episode provided not only the usual 0741 and 0304, but also a 0171 and an 0174.

is it not then in the realm of possibility (and yes, it makes ZERO sense, given the initial 0306... ) that the fuel trims may indicate some danged small plenum rip
P0171 & P0174 almost guarantee a rip in the plenum duct.


I realize my coolant level is a tad high, i'm not running it at dead level to the clear-to-black plastic shading of the recovery tank
Don't take that coolant level too seriously. It doesn't need to be THAT exact. Anywhere from about 1/2 - 2/3 is just fine.

01slsseville
02-19-14, 08:57 PM
SOME dang day my intake coupler will show up... i'll report back after that, and all the rest of the top stuff have been swapped over. so far, as of my last whining and crying episode, the car "only" runs rough. rarely throws any code, and "now" will toss out an 0410 more often than not, ever so rarely even the 0741, although i do baby it / drive like gas is nearly 5 bucks a gallon ( a far cry from twin 850 holleys on a tunnel ram, at what, 35 cents a gallon back then? )

the temp indicator "reality" makes me feel a little better, the only reason i mention it is because in the buck66 miles this old girl has on her, prior to now you couldn't get the needle past noon if you drove it through a time warp on the surface of the sun.

thanks for the help, will report as mentioned.

Submariner409
02-19-14, 10:20 PM
Your engine is calibrated to run on 87 octane. That is $3.879 in Oceanside tonight. No need to baby a Northstar, and you should be getting 13 - 17 city, 17 - 21 suburban, 27+ highway on E10.

04GrandAmGT
02-21-14, 02:09 PM
where I installed Jakes studs. I would never, ever, do a head gasket job again without his studs!!!!

On behalf of Jake, myself, and our company thank you

01slsseville
02-26-14, 12:31 AM
finally got the manifold to tb plenum in, installed it. no change in engine operation, still idles erratically and accelerates poorly (notably at low rpm.) no tear or damage in old plenum, 167k worth of carbon / dirt, though. will still give a random / very intermittent secondary air code, msfire, still cyl. 4, but very rarely trips any code, but always runs poorly. as bad as it runs, it should code instantly, it would seem. acts very much like an air leak, surging at idle, stumbles nv on accel. seems like i'm hearing a fairly massive leak, but cannot locate it. seems to be on rear bank, but wiggle and spray give no change. any diagrams available for all vac line routing besides helm?

thanks

Ranger
02-26-14, 10:59 AM
seems like i'm hearing a fairly massive leak, but cannot locate it.
A stethoscope would be worth it's weight in gold.

01slsseville
02-26-14, 11:22 AM
that's exactly the first thing i took to it after buttoning it back up and hearing the same rythmic hesitation, even before wiggling and spraying witk brakleen for rpm rise and then water for miss reduction. from what i could see of the valves with the intake off, no drama, leakage or excess wear indicators, equal carbon buildup. engine runs "smoother", but the exact same pattern is there. mpg is at 18.9- 19 on freeway. temp climbs as stated before, on hills or other dures, but as you've noted, still well within limits, and promptly settles down after induction conditions depart.

Speedygman
02-26-14, 11:59 AM
How about giving it a drink of water????? carefully??

01slsseville
02-26-14, 05:37 PM
you mean feed it water under load to blow carbon build up out?

MoistCabbage
02-26-14, 06:41 PM
Removing carbon buildup is accomplished through either the WOT procedure described in the Technical Archives, or a chemical top end cleaning product/procedure, followed by an oil change. Do not pour liquid into a running engine.

01slsseville
02-26-14, 08:38 PM
i've read a lot about various people doing that. not something i would be inclined to do, even on a weedeater. as you know, with this engine, witb the intake off you get a pretty goid look at the valves, (per se.) mine are pretty danded decent, no indication ofcarbon loading from what you can see. i was kind of surprised at the amount of accumulation of grime (knowing that's a high % of carbon) in the "forerunner" of the intake. just never saw that thick of a layer i n a dual plane offenheiser or the like, even with the "crude" holley's dumping like the exxon valdez. anyway, only code i got tonight the 20 some odd miles home in snarled traffic was a brief pair of fuel trims, 171 and 174. cannot find a culprit in the vac lines, both plenums are absolutely intact, no loose clamps, etc.

Ranger
02-26-14, 09:04 PM
That is an old trick that worked very well on a carbureted engine. On an engine like the Northstar with a TB and longitudinal manifold it would be much more difficult and dangerous.

01slsseville
02-26-14, 10:21 PM
way outside my scope of faith. i'd have to see it done a few times on someone else's gear. i get the theory, just don't have the cojones (or the wallet) for it. i've been known to #&%+)! up duct tape. anyway, confirm or deny; there is a mathematical difference between an L-88, say, with a near square lobe cam reaching into the heavens pushing a monster stroke; and a ricegrinder type "understroke/overbore" setup that essentially dictates an idle, both smoothness and rythmn. hence our luxo-barges doing ads with nickel on edge on the valve cover, etc. these motors "should" idle with little to any vibration, even with high mileage, so thats half the benchmark i'm chasing. my 96 was a road rocket compared to this skittish like 01, which is ok (it was an sLs also.)

Ranger
02-27-14, 10:22 AM
Perhaps someone can comment on the "mathematical differences", I can't, but I can tell you that the engine should idle smooth enough that you can't tell it's running (other than by sound).

01slsseville
03-01-14, 06:54 PM
after replacing intake gaskets, tb gasket and plenum seal, injectors, injector and fuel rail o rings, and all vacuum and egr lines, the engine runs relatively smoothly / normally, except that it still exhibits a subtle but unmistakeable "miss", oddly enough every several engine revolution cycles, NOT in "every" cycle. The miss is not transmission related, e.g. it exhibits whether in park, neutral, reverse, or drive. DTC's rarely show in "normal" driving, under WOT the DTC will eventually set two lean codes, 171 and 174, and ever so occasionally the 0304 (that was originally an 0306.)

When the intake was off, no evident head gasket failure indications were observed, if indeed any are observable from mere visual inspection.

Is a failed PCM the only thing left to cause this condition, if so is there any further testing to do?

Thanks

Ranger
03-01-14, 08:49 PM
DTC's rarely show in "normal" driving, under WOT the DTC will eventually set two lean codes, 171 and 174,
You have a vacuum leak somewhere. Have you checked the manifold over pressure relief valve?

01slsseville
03-02-14, 12:26 AM
yes, when i had the intake off. i also replaced the nipple connector for the tube. it doesn't hiss or give audible indication of leak. i'll check it with carb cleaner and stethoscope, is there a way to test it besides visually if i pull the intake again? from what i'm able to see, it's pretty much a spring loaded trap door, correct?

Thank you.

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I'll keep on it, I'll find it eventually. At least it's running well enough now to do no damage to itself.

thanks again.

Submariner409
03-02-14, 11:06 AM
I believe that, on your 2001 model, the intake manifold overpressure valve has been moved to just under the plenum spigot - at the "driver's end" of the manifold. The PCV dirty air line snakes around and goes well into the "passenger end" tunnel, attaches to a nipple through the manifold inner wall, and dumps into the intake airstream.

Click a picture to zoom, use your browser <- to back out.

Ranger
03-02-14, 12:26 PM
:yeah: The spring loaded trap door is on the pre-2000 engines.

01slsseville
03-11-14, 09:29 PM
update, pulled intake again to double check everything, you are correct, the "blow off valve" is a pretty muscular, simple to the point of nearly too brick-ish for the rest of the car design. Just a big spring with a hard plastic cap, ribbon of an o ring. Can't imagine a whole lot going wrong with that on any car. Anyway, found a split beginning in the spigot nipple, replaced that. Now all vac lines have been replaced, all vac fittings, all vac anything. On the aft cylinder bank right by the air valve sits a t-bone vac line situation with a one way valve and what looks like another pop off type valve. Wiggle testing showed that pop off looking valve to be erratic, so I just capped off it's line for now. re lubed all the injector o rings, intakes, etc.

Took it out and ran it just a little, still has surging, rythmic idle. Runs ok, no giant hesitation, spools up appropiately under throttle. no codes except, and so far only when pressed hard, still gives a 0304. no discernable miss under load, no pinging or hesitation.

I can get the car back door smogged if needed, and it runs well enough to just drive into the ground as a grocery getter / commuter car.

No reason to leave well enough alone, though, unless it will blow something up, so the quest continues to find the "original" source of giving the cylinder misfire, which, recall, started as an 0306. Any interest / help is still very much appreciated.

Thanks much.

98eldo32v
03-13-14, 10:20 PM
"under WOT the DTC will eventually set two lean codes, 171 and 174, and ever so occasionally the 0304 (that was originally an 0306.) "

Based off the work you have done thus far, you have pretty much covered all the bases. The lean codes at WOT code indicate a possible weak fuel pump. I don't know if you have checked fuel pressure yet.

The rythmic idle/surging at this point, I would pull the valve cover and inspect the cam lobes, lifters and possible weak valve springs.


Yet, with your lean codes at WOT, it could be a pump possibly.......

Good luck

01slsseville
03-16-14, 01:44 PM
i'll check the fuel pressure with a gauge, i suppose i could figure a way to extend a hose to read it at speed / wot as well. the strength of the spray from the schrader valve when bleeding pressure off to work on it seems strong enough to be in the 55 psi range. funny how even after bleeding the fuel rail, it'll still issue a fair jet from the fuel line upon disconnect. (does the fpr provide a block between the schrader and the lines-to-tank? would opening the gas cap help bleed that section, or just time? and if it is just time, where is that point(s) that alows seepage / venting? just curious.)

if the fuel pump is getting weak, wouldn't that cause similar codes across all cylinders, whether misfire or lean? one of the more goofy aspects is that the first scanner reading showed a consistent 0306, only after coil swapping did the code move to cylinder 4, where it has super consistently stayed through injector swaps, intake gasket changes ( on and off several times), etc.
thanks for the input, i'll start with fuel pressure readings.

Submariner409
03-16-14, 02:18 PM
Fuel pressure spec - 41 - 47 psi running.

Ranger
03-16-14, 09:09 PM
I doubt you problem is fuel pressure. If so, ALL cylinders would be misfiring.

Last time I checked mine it was 38 psi at idle. Not sure just how low it would have to go to cause a problem.


i suppose i could figure a way to extend a hose to read it at speed
I simply cut my hose and patched in a length of fuel line hose of the same dia. with brass hose barb fittings. Didn't even need hose clamps.


(does the fpr provide a block between the schrader and the lines-to-tank?
Yes, the return lines. Un-needed fuel is returned to the tank via the FPR. Think of it as a return valve.


would opening the gas cap help bleed that section
No


where is that point(s) that alows seepage / venting? just curious.)
Not sure I am understanding what you are asking.
The tank is vented via the one way (inlet) valve in the cap to replace the fuel that is used. You'll have to define "seepage" better.

98eldo32v
03-17-14, 01:58 AM
http://www.aa1car.com/library/2003/us60324.htm

01slsseville
04-06-14, 09:13 PM
well, an update, after a few weeks of operation. unfortunately, it won't help the next guy with this problem. after checking, replacing, blah blah everything as noted, the engine has decided, apparently on its own, to "run normally." wish i could point to one thing or another as a culprit, but cannot. its been a few weeks, and the engine starts, runs, idles, accelerates, etc, "normally." does NOT throw me any misfire codes, not a 300 or a cylinder specific. still has its original coil packs (well, the ones that were on it when this episode started, i did replace the rear bank ages ago.)

although pretty much all the vac, pcv, etc lines were kind of literally toast and have been replaced, none were cracked, loose, or leaking prior to being handled.

all i'm getting now is a steady tcc code, which i've gone blind reading the hundreds of miles of commentary here on that. down the road somewhere i'll probably take a friday or monday off when the weather is good and go for the 14mm threaded rod deal, crack the tranny and replace that solenoid. right now it's just an annoyance and the thought of losing a few mpg, no crisis. i'll try a tranny fluid change first just to see if maybe that helps at all.

sorry i can't contribute to the database with anything significant / helpful.

thanks all for the help.

Ranger
04-06-14, 09:27 PM
all i'm getting now is a steady tcc code,
Let me guess. P0741?

Submariner409
04-06-14, 09:33 PM
P 1860. Too bad that TCC operation was used as a CAFE dodge - if it doesn't work, it's an emissions failure - the car will not pass state, county, or Fed annual or resale emissions tests.

01slsseville
04-07-14, 12:06 AM
yes, only the 741, have never seen the (more) dread 1860. Please clarify, though, Ranger, if replacing that solenoid is worth the time. If it's a seal inside the trans, the whole thing needs to come out, which is probably not something I would want to attempt, dropping the cradle and all... i paid some 8K or so to have a chevy dealer replace the engine in my '96, and after it was all over with, the speed sensor was "bad".... like you point out, a fifty dollar switch buried under 2800 in labor. I'd imagine dropping the cradle on one of these is a pita even for a line tech.

MoistCabbage
04-07-14, 12:21 AM
Actually, it'd be better to have both codes. That points to the solenoid, which can (however, far from easily) be replaced with the drivetrain in place. But if you have only P0741, replacing the solenoid will do nothing.

With P0741 by itself, the torque converter, and internal transmission seals have to be replaced. Which means the drivetrain comes out. At that point, definitely replace the solenoid.

Your dealer ripped you off BIG TIME for the engine.

01slsseville
04-07-14, 12:29 AM
"Your dealer ripped you off BIG TIME for the engine."

yeah, and he was a "friend"....

thanks for the clarification, it is as Ranger said, then. no point in all that work for nothing. i need to replace the engine mounts, (no engine rocking or anything, just the high speed front wheel vibration) but that's as close to dropping it as i'd prefer to go in my garage.

MoistCabbage
04-07-14, 12:32 AM
If the mounts aren't leaking, and there's no excess movement, I'd start by cleaning any corrosion off of the rim/rotor/hub mating surfaces. And if that doesn't work, a Road Force Balance (checking the rims for true while tgey're off).

Ranger
04-07-14, 10:34 AM
IF, by some odd chance you are not subjected to omissions testing you can ignore the SES light, clear the P0741 code and motor on like I do, but being from Socal, I doubt that will be an option for you.

Here is a better idea of what's going on.
http://www.cadillacforums.com/forums/northstar-engines-system-technical-discussion/149834-information-p0741-p1860-1998-a.html

01slsseville
04-10-14, 02:02 AM
well, in true form, payback for posting an after action report was swift and terrible. even though i had no newly tread ground to share, i didn't want to juzt eat and run without some kind of return. i forget which Chief it was, maybe Susquehanna, that said, take all you want, but put back more than you take.

well, t h e n e x t m o r n i ng after my report, vehicle runs poorly, right off the bat. gives a 306 code, (hey, buddy, how ya doin? remember me? like a bad.mikes hardlemonade commercial.) runs so bad i'm literally going down the road catchin flies. pull into work no overheating, NO symptoms of anything other than massive misfire shudder. off work, driving crappily down the road, get off freeway after a quick, but not fast, 20 miles (got off early.) half mile on surface streets, ac shuts off and temp pegs. its never seen that end of the range.

nurse it home, pull t stat. inside rubber gasket's wrinkly, fine, change it out. full on misfire after. i suppose i can pull plugs tomorrow, but since the misfire is twixt 4 and 6, i'm figuring the worst.
g

98eldo32v
04-10-14, 02:23 AM
You stated before you had lean codes for both banks. P0171 and P0174.

Again what has the fuel pressure been like?

Pull the codes before you pull the plugs.

Post back what the plugs look like.

I hope it's not the worst, but it sounds like it's running in that direction