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Misfire Help Please!

Ryan99639

Ryan99639

New member
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??
 




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
 
cam shaft sensor can cause misfires. Also vac lines that are faulty make it stumble. Heck I seen a temp sensor make a blazer read -40 out when it was 80 degrees guy change spider,regulator,injectors,fuel pump,filter,plugs,wires,distributor rotor and cap. was the temp sensor go figure lol
 


Ryan99639 said:
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
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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.
 
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
 


Ryan99639 said:
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
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Had this same code but mine ended up being the heads hopefully that isnt the case with youres. If you are good with tools do some diagnosing. I checked everything and came down to the valves in the heads and now runs fine.

First if you have the metal covers that go on the wires take them off that solved my issue on another gp i have. Second if you have a junk near you go to it and pull as many sensors as you can from 3800 great for having as spares that is what i do helps eliminate problems without the cost.
Check your Vac lines spray around with carb cleaner.
 
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
 
Ryan99639 said:
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
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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
 
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