I had a probem before with misfiring and I thought I fixed it here with this post here.

http://www.j-body.org/forums/read.php?f=11&i=130558&t=130504#13055

Today after about a week after replacing the cover and the car running fine it started to misfire really bad and then the car died while I was driving. I read the code and it was P0171. After clearing that code I started it up and it was giving a P0300 then.
I pulled the plugs and the plug furthest away from the ICM and then skipping one over are really fouled up. The other two plugs are just like new. So looking at the car straight on and from left to right it's 1 and 3 that are fouled. Inside I can see where the fouled plugs were there is something wet inside at the bottom, oil or unburnt gas? Any clues on this one, Thanks.

take your plugs out.. and gently put a philiphead driver in ther plug holes .. see if you pull out any fluid. i did this to my 96 2.2 on my 3rd cylinder i had coolent really bad in there. in the end i had a cracked head. this #3 was causing a p303 code. misfire on 3

There isn't enough of whatever it is to pull it out. It's just on the bottom and a little shiney where the two are bone dry on thge bottom. I checked the coils and they are in spec.

try the driver technique and get back to me..

Sounds like you have some plugs not firing. Fluid is probably fuel. Another thing could be 2 bad injectors. Maybe staying open, that could have fouled the plugs. I did not read your other post, but did you replace the coils?



FU Tuning

It sounds to me as if one coil pack isn't working. I haven't taken apart the top cover of an Ecotec yet, but usually one coil is used to fire 1&3, and the other 2&4. If the coil measures within spec., then I would maybe look at the module - not properly triggering the coil? It would be nice to have another unit to swap in for this kind of diagnostic, wouldn't it? I would definitely not suspect the injectors, as the likelyhood of two injectors suddenly failing at the same time are rather remote - and I strongly suspect that the wet fluid is fuel.
Once you get it figured out, I would change the oil as it likely is fairly diluted with fuel now.
Good luck!
John



http://registry.gmenthusiast.com/images/2002sunfiresl/Modified%20sunfire2.jpg

I have two other coils and two more ICM to swap in and that didn't work.

Sorry about thinking it was an Ecotec - I should have read the previous post first. I just automatically think of that setup when I read about having a cover with the ICM. Unfortunately that wouldn't have made any difference to my post.
Are all of the boots in good shape? If one is arcing, it can take down both plugs. I realize that you changed some other parts, but I didn't see that you had changed out the boots.
Although I wouldn't think it would be directly related, have you done a compression check? I was trying to chase down a misfire code last year, that turned out to be a burnt exhaust valve. It was specifically affecting only one cylinder though, and the plugs were still clean.
Anyone else more familiar with these? I've only got the LN2.
John



http://registry.gmenthusiast.com/images/2002sunfiresl/Modified%20sunfire2.jpg

OK, figured it out again. It was the housing again. I bought everything new and put it all in and it worked so I switched parts out until it didn't and that was the culprit. The way I
tested it was removing the IDI cover with everything in place and harness still plugged in. I put a plug on the housing tips where they connect into the plugs and had somebody turn the
ignition to see which plug was firing separately. Just as suspected the from the wetness in the two cylinderstwo fouled plugs were not firing at all. After the housing was changed
out all fired properly.

John, you mentioned that it would be a good idea to change the oil after it's fixed. How would the gas mix in with the oil? Also you said that one coil fires 1-3 and the other 2-4.
Is that number counting from left to right on the block? If so that would make sense as it was the 1st and 3rd plugs not firing. What doesn't make sense is that I used a ohm meter
and tested the housing and the two far end plugs go to one coil pack and the two middle went to the other coil pack.

What are the chances of this happening two times in a week with the same part? Could something else be killing the housing? I inspected this housing also and I don't see
anything externally wrong with it. Would it be melting the leads inside the plastic? Hopefully this is it for a year or two when it goes bad again which I'm sure it will.

So for the record for others with these symptoms. The first time it was a random misfire P0300 with good idle, good low RPM speeds and when it was floored it would bog down.
The second time it was the bog at high throttle again but then it quickly went to really bad idle throwing a P0171 anf the car died. After that code was cleared it gave a P0300 with
the bad idle, backfiring, really bad driving like it was not running on all cylinders and dieing very frequently. It sounded like it was running on two cylinders and thats what it was.
How the housing singled out the 1st and 3rd cylinders(counting from left to right) is beyond me. I thought that it would be the two middle or the two end plugs as they are running
from the same coil.

Thanks again for all the help.

If the plugs weren't igniting the fuel, the unburnt fuel would leak down past the piston rings into the crankcase. It probably wasn't enough to cause too much in the way of problems, but an oil change is cheap insurance.

I haven't dug out my service manual to check on the firing order for the 2.4 - I was just going from experience with working on other GM 4 cylinders (2.2, 2.5 OHV engines) and they always had 1-3, and 2-4 tied together (unless my memory is failing again - wouldn't suprise me too much these days!)

I'm glad you figured it out again - things like that can almost make you want to start looking at new rides when they get seemingly impossible...

Greg is right about how the oil could get diluted with the unburnt gas. How badly would depend on how much you drove it that way. I would change the oil if it were mine, but if you want to do a quick check - pull the dipstick and smell the oil. If it doesn't smell like gas, you're probably okay - most of it will likely burn off during a highway run anyway. If it's diluted enough that you can smell it, I would definitely change it soon. Gas doesn't make a very good lubricant.

Hopefully this part will last better than the last one. Are there any bolts used to torque this part into place? If so, perhaps you're slightly over-tightening them potentially causing a part to crack? That's about the only idea I can come up with. Unless perhaps the new one had some rough handling during shipping? Nah - those couriers are always super-gentle, right?

John

Believe it or not it happened again. This time about three days later. Not the nasty backfiring and dieing but a miss at WOT again with no codes. I have a double of every part of
the ignition. Of course the one part that I didn't try was the problem. Tried the rest and even started going after different sensors. I then gave up as I went through everything I had
to throw at this. I got to that point where I start thinking of what new car I wanted so I went to the dealer........blah.

After the initial $86 to basically tell me what I already knew they said they would have to go deeper. Starting with replacing a rubber boot for $120 including part. What a deal huh?
I can replace that and be cleaned up in less than 3 minutes. Well they said it's begin with that part and then start digging or if I leave and replace it myself I have to start with the $86
again if I come back if it wasn't that. So I had to bend over and say stick it in.

Then to my surprise after about an hour and a half they said they fixed it. Turns out it was only 2 of the 4 screws that hold the ignition housing to the alum. cover were stripped
allowing something to spark out of there. They only charged me the $86 which was nice of them but I still had to pay $86 to have somebody tell me that a screw was loose.

I did change the oil after also as it did reek of gas.

So that ends this chapter of find the 2.4 random misfire ...until next time.

so haveing the hole for those super small screws stripped can cause the random misfire code? i find that very odd


owner of 2002 ls sport cavalier and 2007 cobalt ss

It wasnt a hole it. It was the 4 screws that hold the ignition housing tight to the aluminum cover and at first I only had three on there when the problem started. By the time I removed it several times
it had stripped the other one so I only had two screws holding the cover on at one end. Had it been one screw at opposite ends it might have never started the misfire but they were at the same
end. It was basically hanging down on one side and leaving the coils to move around in the housing. It was so simple but I overlooked the most easy solution...loose scews.

I HAVE A 1997 MONTE CARLO LS 3.1 AND I WANTED TO NO WHAT IS P0300 ALL ABOUT