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Alright to start I have a 2001 trans am mostly stock. I am having a problem with the car breaking up in third and fourth and I get a random cylinder misfire codegear under aggressive throttle . the problem comes and goes so I never seem to be logging when it acts up. plugs look good but ill be changing them anyway...fuel filter was replaced not to long ago and the pump was good last time I had the gauge on the fuel rail. any input would be great...


-Dave

Do you have a braking problem, or is the car only misfiring in third and fourth? If it is a braking problem, is it related to the random misfire or are these two different problems?

List of mods that you have done would help, mostly stock is vague.

I meant breaking up...sorry the OP was from my cell phone....but the car breaks up from time to time in third and fourth....and only third and fourth....

It may be a coil starting to go bad. I take it you've checked all the wires when you did plugs? Are you running the stock tune?

those msd coils are not exactly perfect.

How would I be able to narrow it down to one specific coil? The MSD's aren't exactly what I would call cheap. The wires are in good shape, and the tune is spot on....


Ok...lets hear it...whats wrong with my coils?

The misfire and breaking up in specific gear leads me to believe that tuning and ignition would be the issue. Any aftermarket part and tuning will add complication to the car. Why did you swap to msd coils?

Had an extra set laying around and threw em on my car....they have been on my car for well over a year...

If it ever throws a code for a particular cylinder then swap that cyl's coil with another and see if the code moves with it.

For what it's worth I had a set of Accel DIS coils on my GTP that lasted a grand total of 127 miles before they started to misfire. Put the stockers back on and never looked back.

ive always seen msd packs ***** up for no reason. they are a waste of money IMO

what is the engine speed and vehicle speed when it throws the random misfire? what code #'s in particular are you seeing?

i used to run the msd coils, and while i never had a problem with them, i also never had any gains with them.

i would try and swap on the stocker coils and see if that fixes the problem, and while your at it check all the plugs and wires for any defects

after talking to one of my automotive teachers could be a crank sensor hanging up or reading wrong. he thought that may be whats wrong with my car

I've been hoping for it to throw a specific cylinder misfire...but I'm only getting a random....

Personally I've never heard of a problem with the coil packs at all...

It's happening between 4k and 6200 in third and fourth gear....as for the exact code number...I'll pull it later...all I remember is random cylinder misfire...

What sensor or sensors was he thinking?


Thanks for all the input everyone....keep the good ideas coming...

hmmm, maybe a broken/damged valvespring? get somebody who knows hptuners to hook it up to your car and they could see exactly what cyliner is misfiring

I would think if it were the valve spring it would happen everytime and in every gear....I haven't had my HPT hooked up to the car recently...gotta get some logs...I'm gunna lean towards the plugs and wires....

Loose the MSD coil packs they suck... I know a few people that had them and there nothing but problems

^yup... they are expensive and dont do anything for you...

Do you have or have access to HPTuners or some similar data logging software? If it isn't throwing a code, maybe you can at least see what is going on by looking through histograms

Haven't had a chance to log it yet....

yeah if u can, thatd be the best thing to do. it will show what cylinder is misfiring because theres a thing monitors them and counts the misfires

crank sensor my bad

Oh...it's not the crank sensor....I already had the expirience of diagnosing a bad one....

Lose the MSD coils, I had a set and they gave me problems too. MSD makes good stuff for lots of applications, but the LS coils are junk. And they're expensive junk. Can you see if any of the coils(the plastic case) are starting to separate? That is usually what happens. I wouldn't troubleshoot too much farther until you swap them out first.

i would also look for carbon tracing and very light corrosion on the coils.