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Random Misfire Cylinder 1 HELP!!!!!!

I

itsme

New member
ok, i really need some info. my father in law brought his 2000 Grand Prix over, with random Misfire Cylinder One. i also have a 2000 Grand Prix GTP. on His grand prix, we changed the plugs/wires and 1/4 coil. still misfire cylinder 1. so i swapped plugs around within the car, still misfire 1, changed the #1 plug wire with one from my GTP, same issue. Swapped the 1 and 3 injector to see if it would follow the injector, it stayed with Cylinder 1 misfire. checked the part numbers and the ignition control modual under the coils was teh same, so swapped them between cars, same issue. he drove the car yesterday morning for 15mns, said it drove perfect, then when he stopped it started running rough. any idea what it could be? we've done plugs/wires/coil/ig. modual/injectors, nothing has worked! ive never had a misfire like this before. any info is greatly appreciated.
 


was the spark plug smashed when you first changed it?

if you have a chipped piston its used engine time.

if your not sure you can buy or rent a inspection camera and stick it in the cylinder to see if the piston is chipped. (through the plug hole)
 
the plugs all looked fine, well, normal wear and tear, but non were smashed/bent etc. the car only gets driven 1,000 miles a year, as its a backup car. if it were a chipped piston. wouldnt there be smoke out the exhaust from oil blowby?
 
Not usually. The rings on these seal amazingly.

With that little mileage per year, I'd look more toward plugged injector etc.
 
no smoke, but random misfires will happen. as its got low compression now due to the chips

buy, build or rent a camera and look inside its a cheap thing to do to make sure the pistons are all good still.


could also be a bad icm. maybe swap yours to his car see if it helps. icms can test good and be bad still.
 
thanks for the info guys! we did the screwdriver stethascope trick on the injectors, to hear them open/close. one sounded weak, #3 sounded great, so we swapped them, same issue. i was hoping it was an injector issue. he said it happened a few months ago, he cleared teh CEL, and it didnt happen again until this weekend. when it idles, it is rough, you can hear it popping in the exhaust, and see motor shake, when its like 1500-2k rpm sounds amazing, then soon as it idles down its junk again. one thing i noticed kind of random was the idle surged a bit, not all the time, but once or twice when idling it would fluctuate 500rpm's up and down
 


as far as cat no idea, it doesnt throw any emissions codes, the exhaust kinda "pop pop pops" but no strong smell of gas, no smoke, etc
 
Do you happen to have a spark tester? I had picked one up at Harbor Freight super cheap and while it's a simple flashing light..it does help to spot a spark issue.
 
lol, about that...i pulled the plug out, connected the boot, and had them crank the motor, and i did get quite a few shocks lol. we replaced the cap/ignition control modual, plugs/wires. so it should be getting spark, and since it shocked me, ill assume it is.
 


we didnt try with an unplugged injector, we did swap them on the rail though, and nothing changed, misfire cyl. 1. i was hoping it would follow the cap/injector/plug/wire but nothing. it all stayed at injector 1.
 
I'd give it a try.

Reason being is all injectors have power from the same run, but they are controlled via individual grounds from the pcm. So maybe the injector is good and the wire for #1 is having issues. Take a 194 bulb (found in corner light) and bend the two tabs straight. Put it into the injector connector for #1 (not hooked to injector for test) and see if it flashes. It should. It's basically the same as a noid light..just handier and when you are done, you bend them back and put it back into the light.
 
thats awesome! i will try it! i really do appreciate all your guys' help and info! the GTP is the first pontiac i've ever owned, and aside from the rattles on the inside, i like it a lot. i also own a mildly built 05 Neon SRT4 (fun car) and a 1998 honda civic EX (gas saver). but the GTP is the most comfortable for long drives etc. i really am stoked so many people help out on here, on the SRT4 forums its all trolls and little **** head kids giving their opinions and not advice ya know. glad to find a good forum here
 
BillBoost37 said:
Not usually. The rings on these seal amazingly.
Click to expand...

Unless you have my skills ;)
e5azu7yn.jpg

Weirdest part was all it did was wrecked plugs left and right which would eventually make it misfire but until the plug was either wrecked, or the rings were destroyed in piston 3, I never got any misfire codes =o
Fun times.. Good luck finding what the cause is, I'm interested to hear what you find out

Sent from my SM-N900P using Tapatalk
 


that i do not know. he has a guy that works at a BP full service/mechanic shop. dude said cylinder 1 was the only bad cylinde? so im thinking bent valve or something. who knows, never would of thought a random misfire would have been such a big deal lol
 
I've tossed a compression tester on one cylinder and not blocked..gotten low like that. Next one might read right.

That's why I ask.
 
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