P0302

Qman24

Original poster
Member
May 28, 2015
12
I have a misfire that started on my way back from Tampa drove it about 60 miles with the misfire, got back and went to discount auto had the computer hooked up and was reading misfire cylinder #2, I replaced the coil pack and spark plug within the cylinder it seemed to help it a little, it doesn't idle as roughly and accelerates noticeably better but still idles rough and accelerates sluggishly I went back up and had them hook it again and got the same code, they said maybe it was a clogged injector. What should I do? buy a injector and see if that remedies the problem or maybe wait to see if it unclogs it's self I put some Marvel mystery oil in the gas hoping it may unclog itself, I cleaned the throttle body because I've had that cause rough idling before but nothing and I made sure to disconnect over 30 minutes to reset. Is it difficult replacing a single injector?
 

AtlWrk

Member
Dec 6, 2011
674
How many miles on your truck? Maintenance history?
Did you/they clear the code before having them check again?
Assuming your CEL was on solid (code present), and not flashing (damage likely occurring)?
AC Delco 41-103 spark plug?

Definitely do a compression test before looking to the fuel injector.
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
Never heard of our injectors being prone to clogging.

As Altwrk said, if they cleared the code and it came back, I'd probably go ahead and do a compression check. Might as well test all 6 while you're at it.


Furthermore, welcome to the Nation, you've came to the right place for help. :yes:
 
  • Like
Reactions: Mooseman

Qman24

Original poster
Member
May 28, 2015
12
I was trying to find the carfax papers, this Envoy has a branded title so the mileage reads as 89k but probably closer to 120k.
the codes were not cleared I was not aware they had to do that..should I go back to the store so someone can do that? I had the noobie help me as opposed to the guy who came out and did it in a few seconds the day before, she took a few minutes and didn't even ask to start the car like the other dude..
it was replaced with a AC delco iridium I don't know the numbers but it was adjusted before being handed to me they were already at factory spec. I'll try to find the papers I know some work has been done, one coil was replaced already.


My code light goes from solid to flashing.


Should I rent a compression tester from the discount and do it myself? It's not too difficult right? Just remove the coil packs and spark plugs? I know the 6th one is a bitch to get to.
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
Yeah, get the code read again and cleared.

When the light starts flashing, it's figuratively screaming at you, telling to turn the engine off before you melt the catalytic converter.

But get the code read again and see what it tells you. If it's still p0302, do a compression test asap before throwing anymore parts at it.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Even if you don't get the code cleared, it should clear itself after a couple of drives if the problem has been resolved. If it stayed on, then the code is either still there or there's another one. Get it read and cleared again. The flashing light just means that it's an intermittent ignition miss, not any worse than a steady light. If you replaced the coil and still no joy, I would do a compression test on all cylinders.
 

Qman24

Original poster
Member
May 28, 2015
12
It's not running as horrible since it first occurred, after replacing the #2 coil and plug it seemed to have helped a little, I need to go ahead and replace all of the plugs.
 

Qman24

Original poster
Member
May 28, 2015
12
Qman24 said:
It's not running as horrible since it first occurred, after replacing the #2 coil and plug it seemed to have helped a little, I need to go ahead and replace all of the plugs.
I went and got the code cleared but still reading#2 misfire, after the code was cleared it was actually reading multiple misfires giving a P0300.

I will have to wait until Wednesday to do anything with money. What should I do? Rent a compression test kit and get to testing?

What will I confirm after the compression test? Could this be bad valves?
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Or confirm that the engine is mechanically healthy. If you have compression, then it's time to look somewhere else.
 

Mike w

Member
Jun 24, 2014
287
I live nearby if you need help. Just to mention it is easy to put the coils in wrong. I have new coil boots if you need one.
 
  • Like
Reactions: Mooseman

uncafreddy

Member
Jul 20, 2015
4
Checking the injectors should be the very last resort, as they are buried under the intake manifold. It would be way cheaper, like free, to check the wires to the coil. They sould be ground, 12volt and a pulse signal (the middle wire at the connector) to fire . Mike w, the new coil packs usually come with a new boot installed.
For future ref, if the coil pack is suspect, and you have a p0301-6, swap the coil to another plug and see if the problem moves. Sometimes it takes a few miles for the PCCM to decide which cyl is missing, so it issues a p0300 in the meantime.
BTW, a basic code reader is fairly cheep these days. I keep one in my 03 Envoy in that cool compartment under the way back floor. A volt meter is also a good, low priced investment.
 

Mark20

Member
Dec 6, 2011
1,630
I've had a rough idle for a little while and an occasional flash of the CEL but until recently no codes to read. Changed the spark plugs for 100K service and the engine is running worse but I finally got a #6 misfire code. Thought it was the coil but after swapping it appears not. The #6 plug was charcoal colored indicating misfire. Others were normal ash tan. From some reading here, at the OS and elsewhere it seems the intake manifold gasket may be the cause. I checked the tightness of its rear nuts (except the rear most ) but no improvement. Can't look at it for several days but will keep you guys informed.
 

Forum Statistics

Threads
23,273
Posts
637,499
Members
18,472
Latest member
MissCrutcher

Members Online

No members online now.