Thread: Misfire Help Please!

ok so since i bought the car two months ago it has been misfiring terrible at idle, all the cylinders are misfiring on my aeroforce gauge and the car drives smooth down the road just the idle is ridiculous. just a note i have replaced spark plugs, plug wires, and idle air control valve all with brand new parts and i am getting sick of the elimination progress because its getting expensive, anyone have anything like this or any good advise??

Have you replaced vacuum lines yet. They may look good but probable have cracks in them.

nope didn't think of that, I've got a few that don't look to good now that I think of it

Get your icm checked out too

ignition control module? right

Yep

at first I brought it to a shop to let them check it out, they told me they were going to replace that screen that goes over the throttle body to see if that works, I said ok when I asked how much they said $150 after parts and labor haha I just took it home at that point

That screen shouldn't cause any misfires but will cause a rough idle

is it more restrictive if I put it back on? it wasn't on the car since I bought it

Originally Posted by Ryan99639

at first I brought it to a shop to let them check it out, they told me they were going to replace that screen that goes over the throttle body to see if that works, I said ok when I asked how much they said $150 after parts and labor haha I just took it home at that point

whats wrong with your maf screen that they wanted to change it? its there to smooth out the air flow as it passes the maf, so it gets a better reading.

and from what ive seen here, its hit or miss how your car will idle with out the screen. some do just fine, others dont.

Put a screen in. It's there for a reason.

i say vacuum leak somewhere maybe even injector o rings. no1 i know has the maf screen on... is the code for multiple cylinder missfire or does it actually point out which cylinder?

right now my scangauge is giving the p0300 code and I clear it and it comes right back, but when I watch the misfires on the scangauge it moves around through all of them it's not one cylinder sometimes one will be bad for a couple seconds then it will change to another one, but the moment I take off or give Any throttle all cylinders go to zero misfires Until I stop again it's so weird

ok I'll have to do that then too, how did you find out it was the heads? and what was wrong with the valves? that sounds like a major pain

Originally Posted by Ryan99639

ok I'll have to do that then too, how did you find out it was the heads? and what was wrong with the valves? that sounds like a major pain

Alot of diagnosing and switching out sensors like, icm, coils, o2, anything that had to do with that code which is why its good to have extra parts. Once i ruled all that out, compression test, once i had 2 cylinders with 0 compression did a leak down test and found out they were leaking exactly from the intake valve.
Trust me it was especially when i just put in the engine into the car and had to pull the heads 1 day later and put it back togehter in the car.

Best thing to do is diagnosing its a pain but the more you learn and work on the car the easier it will be next time you have the issue.

very true, well I hope I don't have to take it that far but like u said I gotta keep diagnosing it as much as possible I'll probably try the sensors, throttle body screen and coil packs next I guess