Misfire with P0300

[Justin.Kirkham]

Re: Misfire with P0300

So I checked the electrical stuff again today, and checked the fuel injectors, as best I could (I listened for the clicking and checked the resistance of the injectors). Everything seems find with those.

I'm headed to buy a fuel pressure test kit now. I'll let you know the results.

Tim - As far as the hard starting - maybe. The only other thing I notice is the smell of fuel, since the new misfire, when the car is running. It is most obvious from the exhaust.

WhitDog - The coil packed weren't rusted, but both were from Advanced Auto Parts or Autozone. Given the above, however, it seems that maybe this time the coil pack was not needed.

-Justin

[Justin.Kirkham]

Re: Misfire with P0300

Here are the fuel pressure measurements that I just took:

Engine off, with key in ON position: 40 PSI (There are a momentary spike to 50 PSI, but it lasted for less than 1/4 second. The pressure then dropped to 42-40, but rested on 40 after a few seconds.)

Engine ON, at idle: 33 PSI.

So, the problem looks fuel related to me. I am guessing that the fuel filter is the culprit, since when I looked at it, it looked horrifically rusted and I am not sure if it has ever been replaced (car is a 2000). Any other ideas before I go ahead and replace the fuel filter?

-Justin

P.S. Thanks for the fuel suggestion, Tim.

[ssms5411]

Re: Misfire with P0300

If not the filter then its goes to be the pump or the FPR.

[thedetailman]

Re: Misfire with P0300

your icm is bad,
BELEIVE it or not

I bought 3 new coil packs and a icm from junkzone (autozone) and a week later. the coils went out. i turned them in and got three new ones. and a week later those were bad.

i then had the icm checked and BAM it was bad. So i replaced that with ANOTHER autojunk one and that one lasted about a month. and then started destroying my packs again. (they had never heard this.) being pissed. i gave it all back. got my money back and went to advance auto parts and got the coil packs from there and the lifetime warrenty icm from oreilys.

so far they have been GRRREAT :D going on a year now with no problems what so ever. and YES icms can make 1 or 2 or all your coils go bad. so im guessing its your icm. they run about 150 bucks give or take 20 bucks.

hmmm i have one for sale though :D for 20 bucks.

[Scrat's_Camaro]

Re: Misfire with P0300

pull the vac lines on your fpr. i had the same exact problem as you are having and come to find out fuel was getting in the vac line from the fpr. as soon as i replaced the fpr, i never had a misfire since and its not expensive to replace.

[whitdog54]

Re: Misfire with P0300

I was thinking ICM also like I said I before. I would go to junkyard and maybe find a low mileage 3800 like a grand prix or another firebird or camaro. Grab the coil packs off that. I believe the ICM on the grand prix is the same too, but imk not positive.

[Justin.Kirkham]

Re: Misfire with P0300

So I replaced the fuel filter (and the air filter since I was under there), and the misfire is much better... but still very much there. The idle is rough, yet at high speeds, the car seems fairly normal. The misfire isn't nearly as harsh now - almost more like a backfire than a stumbling "about to stall" misfire. So that just confuses me even more. I'll admit that I am about to just give up and take it in. I feel like I am fumbling in the dark a little here.

Tomorrow I will take fuel pressure readings again, and I will check the vacuum line off the FPR. After that, maybe I will try the ICM idea before I cave in to the dealership.

-Justin