Engine misfire

[AMRCNBA]

Car is a 98 firebird 3.8.

Throws the p0303 engine misfire code whille driving. Car studders slightly. Car was throwing a code for an EGR valve pintle position performance, and the car was driven some while that problem occured. The EGR valve was replaced, and that code is gone. The spark plugs have all been replaced and the old ones looked like a set of old plugs, nothing to speak of. Fuel filter has been replaced. Problem still occures. You don't even have to drive amile, and the studdering happens. I can clear the codes, and within a mile the problem and code reoccures. PCV valve rattles, so best assumption is that it's good.



Do the ignition coils fail on this motor often enough to speak of?

Does the crank position sensor fail often enough to speak of?



Ways to test either of them? Does anyone know of the ohm reading for the primary and secondary side of the ignition coil so I can test them?

Car has about 99,000 miles, so at this point I guess the o2's could be to blame. I have Autotap, so if there is anything pertaining to it, feel free to advise. I have several o2's from my v8, will they swap over to this car?

All help is appreciated and needed.

[SehlraC]

Crank position sensor failure isn't very common with the 3.8's, but coil packs are. Also, a common thing is spark plug wires failing due to being so close to the exhaust manifolds. Do you still have the heat shield boots on the appropriate wires?

[AMRCNBA]

Yeah, all of the shields are still there. Any source for the coil packs other than the dealership? Sold individually or in packs of 3?

[hrspwr00v6]

okay... its one of 4 things, Plugs, Wires, Coils or ICM. Coils normally fail due to heat.

[AMRCNBA]

I checked the plugs, wires, and coils and they all checked out fine. I'll check the module tonight, but I have my doubts. I may have a plug wire making an intermintant connection or failing once it gets hot. I'll try again tonight.

[20firebird02]

might also want to check ur cats and make sure they r not cloged up. that is what happened to mine. spent 300 bucks on new coils, wires, plugs and come to find out it was the cat.

[AMRCNBA]

When your cats failed did you get any codes for slow response O2's or the 3rd O2 sensor throwing any codes.

I'm actually looking at the IAC valve right now. While the car is just sitting there, not running, the IAC is clicking a few times randomly, and then the car will throw a code, once the car is running it then throws a mnisfire code.

[20firebird02]

no codes about the o2 just a misfire code. also the ses light would flash (misfire).

[hrspwr00v6]

Originally posted by AMRCNBA
I checked the plugs, wires, and coils and they all checked out fine. I'll check the module tonight, but I have my doubts. I may have a plug wire making an intermintant connection or failing once it gets hot. I'll try again tonight.

i don't think the plug wires will 'intermittenlyfail' once they are gone.. they are gone. i'm sayin' its probably your coil packs...
when they are cold they will test fine. car will run fine. when they get hot thats when they decide to crap out.

[AMRCNBA]

I believe the coil packs are OK. I switched them all around, all checked out fine with an ohm meter primary and secondary sides, and the car doesn't have to be hot to act up. The IAC Ohm reading was fine. Apparently the car will activate that thing at times even if the car is not running. Both of the other cars I looked at did it. Tonight the plug wires get changed and if that's not it, I'll just set fire to the whole damn thing.

[Nightrida]

i have the same problem and feel the same way. do you have huge power loss? i am getting p0300 but i also have a cam throwing the same code. my tuner thinks he deleted that code though. my misfire history is on cyl5 mostly the 6 is second most.

[AMRCNBA]

Yes, there is a power loss, although once the problem occured, I stopped driving the car. I have cylinder number 4 misfiring, with 0 misfires on all other cylinders. Numer 4 is misfiring on average 140 to 150 times every 200 revolutions per minute.

[Nightrida]

i was shocked when i saw 44000 misfires on cyl 5 and the others were like 20

[hrspwr00v6]

pull the plugs/wires
switch to NON platinum plugs and some goood wires (aka Taylor Moroso etc)

[Nightrida]

i have ngktr5 plugs gaped at .060

[Nightrida]

i think i found my problem. cyl 5 coil dies under load. bu sparks at idle.

[hrspwr00v6]

replace them all with accel or MSD stuff. not cheap, but will help with spark delivery, hell you might accidentally pick up a pony or two :shrug:

[hrspwr00v6]

actually i think OEM replacements are ~27 bucks, and i think the Accel or MSD are like 33. (thats per coil mind you)