: surges/sputters while driving, but idles perfectly fine?



Rattlehead
01-18-12, 06:45 PM
Hey, my first post even though i have been all over this forum for the past few days, seems its hard to find my exact problem

basically its pretty much the same as this post:
http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/217903-bucks-sometimes-stalls-only-under-load-2.html

im not sure if i would say it bucks, but while i am accelerating at a steady pace the RPM's start going up and down which makes the car surge forward and back, the car seems to bog down a bit with each surge the more gas i give it, and if i give it too much i can hear a sound kind of like lifters tapping with the surge, and every once in a great while the engine will stall.

if i give it very little gas at a steady pace it seems not to surge, but im talking maybe a 1mph every 30-60 seconds, at first i was thinking transmission, but then i pulled the DTC codes:
P1599 history
B0429 current
P0101 current
C0660 current

ok, so like a noob, i replaced the MAF sensor, made sure everything was tight, reset the codes, and it still does the same thing, and still spits out the same codes after a drive cycle. i actually started this with a fuel pump, and a fuel filter, then the MAF sensor, still does the same thing, i cant find any vacuum leaks but i did find out that if i pull my PCV out a bit to simulate a vacuum leak, then it does the same thing but a tad worse, and throws the same codes, and to test it futher i pulled the plug from the MAF sensor and the car does not do it at all with the sensor unplugged, granted i know that it goes into a type of default mode at that point, but that allows me to rule out most mechanical issues i hope.

so far im about $400+ into this fix with 0 resolution, i bought a TPS but have not installed it yet, as i have no clue at this point if thats going to be the issue, or if its going to be the crankshaft sensor like the post in the link above (like i said, not sure if i would say it 'bucks' and i know a crankshaft problem might cause it to buck) or IAC or a number of other sensors that work together with the MAF, im really tired of buying part after part and nothing changing, so i am hoping someone here could lead me in the right direction before i give her an old fashioned viking funeral . . . .

Ranger
01-18-12, 09:37 PM
If I understand you correctly you replaced the fuel pump? If not, check your fuel pressure. Make sure the intake ducting is properly connected and clamped tight. Check the plenum duct for a rip (vacuum leak). Give the TB a good cleaning.

Rattlehead
01-18-12, 10:20 PM
yes, items i have replaced:

Fuel Pump
Fuel Filter
Mass Air Flow Sensor


I have also purchased a Throttle Position Sensor, i have checked the plenum and the entire duct for leaks, all clamps are tight no signs of cracks or even hardening on the top or the bottom of either, checked to see if the fuel regulator was leaking and it seemed fine as well, although i cant be sure. i haven't cleaned the throttle body yet, but from what i have read in the post i mentioned he had cleaned his well and still had the same results, this isnt an excuse not to clean it, i had already planned on it, i just wasnt relying on that to be the fix for this particular issue.

i have also noticed that i cannot find a ground on the IAC plug, i can find one on the MAF and the TPS fine, but not the IAC, i dont know if this would make it run liek it does, because it idles beautifully, i can rev it and it sound great, so i dont understand how the IAC could, but maybe?

tateos
01-18-12, 10:33 PM
I think Ranger could be on the right track when asking about the plenum duct. What is your idle vacuum reading? What about the intake backfire valve, guys? I can't remember the setup on the 2000+...could that be a source of a vacuum leak?

You've seen this (with a nice video) or something similar?:

http://www.obd-codes.com/p0101

Rattlehead
01-18-12, 11:12 PM
checked the plenum, checked the duct, top and bottom, both visually and physically, i dont have a vacuum gauge, but i can tell you when i take a vacuum hose off i can stick it to my finger, it has 'a lot' of suction lol.

and yeah, i know what the p0101, thats why i replaced the MAF sensor ;)

Submariner409
01-19-12, 04:53 PM
The rattle that accompanies the acceleration surge - this smells like a faulty/excessively dirty EGR valve. The 'rattle' is detonation caused by incorrect mixture control - stuck/sticky EGR - and would not be caused by the MAF, which was probably OK.

Ranger
01-19-12, 09:58 PM
I think Ranger could be on the right track when asking about the plenum duct. What is your idle vacuum reading? What about the intake backfire valve, guys? I can't remember the setup on the 2000+...could that be a source of a vacuum leak?


The manifold over pressurization valve on the 2000+ engines is under the TB. Possible, but not probable.

Submariner409
01-19-12, 10:20 PM
Read post #6 again..................

Here's the 2000 and later overpressure valve - a spring loaded mushroom valve.

Rattlehead
01-19-12, 10:32 PM
well today i took off the intake duct to the TB and cleaned it out with TB cleaner and a small toothbrush, this made it drive ok for a bit, was still hesitating a small bit, but so much better then it was before, but after a few drive cycles the service engine light came back on and it started running like crap again, still not as bad, but same symptoms just the same. i also sprayed the outside of all the vacuum hoses i could reach, as well as the plenum and intake duct, with the TB cleaner while the engine was running to see if my idle increased at all so i could maybe find a leak i couldnt see or feel, but i didnt get an increase in my idle at all, but this is a 2000 caddy, so im not sure if this kinda test will even work on it, but it was worth a try ;)

tomorrow i plan on cleaning it out again, just to make sure i did a thorough job (never cleaned a TB before :P ) and while i am at it i will pull the EGR and check it out/clean/replace. since my TB was filthy (and it was, like an oven thats never been cleaned!!) im wondering if maybe its affecting the sensor that sits on top of the TB, i am assuming that it is the MAP, looks like its being held in place by the cable bracket, but it seems loose, i can turn it from left to right, again im a novice so it could be the way its supposed to be, but none of the other sensors are loose like that so it is a concern for the moment (until u guys tell me otherwise).

so, if i clean the TB again, and the EGR, and it still does it, what would u guys suggest i go next?

tateos
01-19-12, 11:34 PM
The manifold over pressurization valve on the 2000+ engines is under the TB. Possible, but not probable.

OK thx Ranger - I know that has occasionally been a problem on the <2000 MY N*s

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It's just barely possible the reason it ran better after the TB cleaning is some residual cleaner puddled inside the intake manifold and caused a temporarily richer mixture...

I think it's OK to poke around and clean stuff, but I wouldn't recommend you replace anything else like MAP sensor or EGR valve on a whim - you've already thown away $400, and it's cheaper to just go somewhere and pay for a diagnosis and/or repair

Submariner409
01-20-12, 10:02 AM
The MAP sensor is a press fit into the top of the throttlebody: its tip has a seal ring - and the thing will be easy to turn left and right - the throttle bracket tang simply keeps it from wiggling out.

The throttlebody - remove the intake ducting and block the throttle wide open - use a golf club or some such wedged against the front of the seat to press down the gas pedal. Scrub out the TB as far as you can see - use toothbrushes and lint-free rags. Try not to get excessive amounts of cleaner in the manifold - it simply puddles in the center log and goes nowhere.

Same for the EGR - lift it out and clean the pintle and manifold bore thoroughly. careful - don't get much cleaner up the shaft toward the solenoid.

Click on my username, open my profile, then the albums. 6 pages of Northstar engine stuff from 2000 on.

This is for an STS, but the parts are the same............. The EGR sits on the water crossover right in front of your gas pedal foot.

tateos
01-20-12, 12:13 PM
That's one heck of a picture, with labels, Sub!

Submariner409
01-20-12, 04:33 PM
Go back through my albums in my profile - did some more picture/notes homework the other day.

Rattlehead
01-20-12, 09:14 PM
well, i cleaned the EGR, thought it was running really well, better then it has since i have had it, then when i park it after a test drive the service engine light comes on (i had cleared the codes after i put the EGR back on) and got some EGR codes, turns out i forgot to plug the pig tail back into the EGR, after plugging it in i test drove it again, and its running the same as it was before i cleaned it.

without it plugged in it drives so well, is this a sign of anything?

Ranger
01-20-12, 09:30 PM
since my TB was filthy (and it was, like an oven thats never been cleaned!!) im wondering if maybe its affecting the sensor that sits on top of the TB, i am assuming that it is the MAP, looks like its being held in place by the cable bracket, but it seems loose, i can turn it from left to right, again im a novice so it could be the way its supposed to be, but none of the other sensors are loose like that so it is a concern for the moment (until u guys tell me otherwise).
Yes, that's the MAP sensor and that is normal.

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well, i cleaned the EGR, thought it was running really well, better then it has since i have had it, then when i park it after a test drive the service engine light comes on (i had cleared the codes after i put the EGR back on) and got some EGR codes, turns out i forgot to plug the pig tail back into the EGR, after plugging it in i test drove it again, and its running the same as it was before i cleaned it.

without it plugged in it drives so well, is this a sign of anything?
Exactly how did you clean the EGR valve? Did the pintle valve move freely with no resistance or sticking throughout it's travel?

Rattlehead
01-20-12, 10:00 PM
i followed this post, i cleaned it just like it told me:
http://www.cadillacforums.com/forums/cadillac-tech-tips/59077-how-clean-egr-valve.html#post523588

the pintle seemed to move freely as well, easy to push down, popped right back up when released, i actually didnt get alot of anything out of it when i cleaned it. i have test drove it again with the pigtail off again just to be sure my theory was correct and it does indeed run like a champ with it unplugged, prolly not very good for the car tho, plus my inspection is up and the codes will cause a fail, however its easier to get down the road to the store with it off lol, i really feel like this is something that i shouldnt take it to a shop for, i have some trust issues with the local shops for reasons i wont get in to here, but even taking it out of town somewhere im sure they will charge me an arm and a leg and it will turn out to be something i could had saved hundreds of dollars on AND know its done right if i were to do it myself.

what would u suggest i do next?

Ranger
01-20-12, 10:31 PM
Have you checked for a leaky FPR?

Rattlehead
01-21-12, 02:38 AM
i popped off the vaccum line to the FPR and checked for a smell of gas at the hose, and for any fluids, kinda smelt like gas, but the whole engine kinda does, no signs of fluids at all with car running or not.

Dr. John
11-05-12, 11:28 AM
If I understand this thread correctly, I have developed a similar problem on my 2005 STS with Northstar RWD. Eager to know of any solutions that worked.

N.Williams
08-29-14, 08:40 PM
Did you find the problem?My caddy has the same symptoms.

Submariner409
08-29-14, 08:55 PM
The thread has been dead for almost 2 years, Please update your profile to show proper information and consider setting your post/thread preferences to "View latest posts/threads first". That way, you see current information instead of digging up bones. Time zone - Do you really live in London - GMT ?