01 Seville runs rough, 0306 code intermittent
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Northstar Engines and System Technical Discussion Discussion, 01 Seville runs rough, 0306 code intermittent in Cadillac Engine Technical Discussion; tomorrow i'll switch injectors (checked with stethoscope, all clicking normally / alike) and do a compression test. after going blind ...
  1. #1
    01slsseville is offline Cadillac Owners Member
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    01 Seville runs rough, 0306 code intermittent

    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.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: 01 seville runs rough, 0306 code intermittent

    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.

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    Ranger's Avatar
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    Re: 01 seville runs rough, 0306 code intermittent



    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.

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    Mark D is offline Cadillac Owners Member
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    Re: 01 seville runs rough, 0306 code intermittent

    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.

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    01slsseville is offline Cadillac Owners Member
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    Re: 01 seville runs rough, 0306 code intermittent

    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.

    ----------

    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.

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    Re: 01 seville runs rough, 0306 code intermittent

    Quote Originally Posted by 01slsseville View Post
    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...60-1998-a.html

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    01slsseville is offline Cadillac Owners Member
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    Re: 01 Seville runs rough, 0306 code intermittent

    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?

    : )

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    01slsseville is offline Cadillac Owners Member
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    Re: 01 Seville runs rough, 0306 code intermittent

    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.

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    Re: 01 Seville runs rough, 0306 code intermittent

    Quote Originally Posted by 01slsseville View Post
    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.
    97EldoCoupe likes this.

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    01slsseville is offline Cadillac Owners Member
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    Re: 01 Seville runs rough, 0306 code intermittent

    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?

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    drewsdeville is offline Cadillac Owners Master
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    Re: 01 Seville runs rough, 0306 code intermittent

    Quote Originally Posted by 01slsseville View Post
    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.

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    01slsseville is offline Cadillac Owners Member
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    Re: 01 Seville runs rough, 0306 code intermittent

    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 (?)

    ----------

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

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    Re: 01 Seville runs rough, 0306 code intermittent

    "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.....

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    Re: 01 Seville runs rough, 0306 code intermittent

    Quote Originally Posted by 01slsseville View Post
    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?

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    Re: 01 Seville runs rough, 0306 code intermittent

    Quote Originally Posted by Ranger View Post
    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 ?

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