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misfire with low acceleration *HELP*

lilump

lilump

New member
I have 2001 Grand Prix GT 3.8L. Idles smooth, from stop 2 start it jerks just a little. not really bogging down alot. Also when I get up 2 around 40-50mph and apply steady low acceleration to maintain speen slight jerking comes again. With hard acceleration it will buggy with no problem. I just changed spark plugs (AC Delco) and wires, and fuel filter. No change. Please, any ideas? Thank you
 


I think i might have the same problem. when going 40 to 50 does it seem to jerk under light throttle when it holds its current gear, but under hard acceleration it downshifts and then there is no problem?
 
lilump said:
yes that is it! I don't know what is wrong. Do you?
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Muffler Bearings, I'd replace the whole cat-back system or grease the bearings :th_laugh-lol2: j/k j/k

Mine did that too, i think it has to do with the line pressure or possibly maybe need a service, I got a tuned pcm that up'd the line pressure and did a service just prior to a filter fluid change, doesn't do it anymore... food for thought, good luck
 
my mechanic said there was a regal in with the same thing and it turned out to be the mass airflow sensor.

not sure if it's the same exact problem, but another thing to check. I also have new plugs and wires and it still does it.
 


EJOUIE said:
my mechanic said there was a regal in with the same thing and it turned out to be the mass airflow sensor.

not sure if it's the same exact problem, but another thing to check. I also have new plugs and wires and it still does it.
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Pull off the MAS and see how it looks. I would start there. You can unplug the MAS and see if that makes a difference in how it runs. If there is no change then you could be looking at needing to get a new one.
 
Do you have SES?
What are the scanner codes (all)?
New wires and plugs?
If yes, what "P" codes (from above) are you getting?

Check the coresponding Ignition coil.

Turns out, we have 3 coils each sparking 2 cylinder plugs (always the same 2).

COIL-POSITION CYL-POSITION
(Closest to the windshield)
TOP: 6, 3
MIDDLE: 2, 5
BOTTOM: 4, 1
(Closest to the radiator)
 
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SuperStarr01 said:
Pull off the MAS and see how it looks. I would start there. You can unplug the MAS and see if that makes a difference in how it runs. If there is no change then you could be looking at needing to get a new one.
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Pull the MAF sensor out, and if its not a pretty shiny end, take some brake cleaner (brake, carb, b12, etc... SPRAY cleaner) and spray it clean, then let it dry and put it back and see if it makes a difference, DO NOT touch it with anything, its a fine tuned sensor and with age can be brittle and break if you touch it, it wont break under normal conditions just spray it clean vs using a q-tip and alcohol... :th_thumbsup-wink:

most likely a tranny issue, a 40mph lag or shutter occurs in some from what ive seen... not sure on a solid fix tho
 
surprisingly enough, it isn't setting the ses light. I was getting some misfires before, but the new wires fixed that.
 
The tranny issue makes sense. I had a Silverado that you could watch the tack jump over a range of 500 RPM. After I changed plugs, wires, coils, it turned out that I need a new tranny and lock up converter. That fixed the problem. Check the fluid level, and smell the fluid. I know amsoil can do a test on your tranny fluid to check how bad it really is.
 


SuperStarr01 said:
Pull off the MAS and see how it looks. I would start there. You can unplug the MAS and see if that makes a difference in how it runs. If there is no change then you could be looking at needing to get a new one.
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you have it backwards.

if you unplug it and the issue stops, then its the MAF sensor.

If it persists, then the MAF is not to blame.
 
Please dont use brake cleaner on the maf, use Maf cleaner. Its very sensitive. The Maf also effects tranny line pressure. So this could very well be the issue.
 
just because the ses light isnt on doesnt mean there isnt a code. i cant tell you how many cars ive scanned at work that had lots of codes but no light.
 
thanks for all your replies. I took it up to autozone to put it on the diagnostic thing. They said it read the EGR valve or cat. converter. If it was the cat. converter, wouldn't it run alot rougher & not have much power?
 
that doesn't seem to make sense. both of those seem like it would cause a more consistent problem. at least with mine, it is inconsistent. i am still thinking its the MAF. I tapped mine a bit while the car was idling and i could notice the engine struggle a bit.
 


well if its the egr it would have read an egr code if it was the cat it woulda been a catalyst inefficiency code. id say you got a cat problem. if you know how to cut and weld, cut the exhaust just before the cat and drive it. yes itll be loud but if you get better performance then you know you got a clogged cat. if its the egr get some carb cleaner and a toothbrush and start cleaning. or buy a new one. theyre about 160 bucks.
 
EJOUIE said:
that doesn't seem to make sense. both of those seem like it would cause a more consistent problem. at least with mine, it is inconsistent. i am still thinking its the MAF. I tapped mine a bit while the car was idling and i could notice the engine struggle a bit.
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Just a thought, IF the MAF isn't reading right, wouldn't it throw off the computer on air-fuel ratio, causing more or less fuel than necessary, possibly causing the egr sensor to be off the norm and the excess fuel or lack of enough fuel to be causing the cat to be overworked????

alot to happen just because of 1 sensor but isn't that why we have the sensors?

anyone want to dispute my theory? :confused:
 
^^^ i am thinking that is close to whats goin on. the maf is causing some trouble and using other car parts to take the blame when the mean ol OBD II comes checks thing out.
 
Well guys, I got some MAF cleaner this morning & cleaned the MAF sensor. I'v been driving it around & its had NO misfire (knock on wood)! I will continue to monitor it. Thanks alot for everyones input! Especially EJOULIE & TLSHEFF! Thanks
 
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