P0300 and P0305 Codes
 

Hello All,

I have a 2006 H3 with 63800 miles on it, adventure and lux package. Last week I got my first Check Engine Light and when I scanned it, sure enough it was the P0300 random misfire and P0305 cyclinder 5 misfire.
A week PRIOR to receiving the code, I changed the spark plugs to AC delco iridiums gapped at .041. I also cleaned the Throttle body and MAF properly.

When I received the two codes last week, I swapped coil pack 5 with 4 and cleared to codes, to see if the problem would move. Well it didn't, and now my check engine light is back on, and received only the p0305 code again.

I've read a few other threads, but it doesn't seem clear as to what I can do before taking it to a stealership?

Should I do a compression test?
Would replacing the coil pack be useless since it stayed in 5 after swapping the coil pack?

Are there any other options to resolve this? I do not feel a rough idle, fuel economy is 14 MPG with 33 inch MT's and a roof light/rack.

Thanks all!

IMHO I think it's a bit soon to do the extreem.
Following:
Replace coils
replace sparks
Clean tb
Clean maf
Replace injectors
tighten intake manifold

Just some thoughts.
Chris

By extreem I mean head.
Chris

From an old post of mine to a similar question: "Go back and revisit what you did. If you do not have a coil packs on straight and snapped down in proper position before you tighten the retainer bolt, you will have issues."
and ....
"When you place the coil on plug pack back on the new spark plug, you have to put it back on the plug like a regular spark plug boot. Make sure the plug goes in the boot and the boot is all the way down and centered on the plug, then tighten the retaining bolt.

The contact with the plug is made by a spring under the coil to the plug, if it is crooked, or the plug insulator boot is hung up, it might be a bad connection and cause a miss."


Did you happen to drop one of the plugs?

Simple stuff first. Since you are only getting a P0305, remove the #5 plug and put in a new one, like anything man made, you can get a bad plug (cracked or defective), and how much is that going to cost you? See if the problem continues.

Thank you chris and doc for the info.
To answer your question doc, I did not drop any of the plugs while installing them, but I put them in with my hands and slowly lowered them into position, hand tight, then used a socket to finish.


There's a good chance it's my fault the code appeared because it was my first attempt at replacing spark plug and cleaning t-body & maf. But if I had a crooked install on the 5th coil pack, wouldn't the code have moved considering i switched 4 and 5?

I've already replaced plugs, cleaned tbody and maf so now i'll attempt to tighten the exhaust manifold and install a new coil pack into the 5th position.

I will report back in once I take another look at it.

just an idea, try switching plugs 3 and 5 and see if the mis-fire moves.
Hope it helps. and good luck, I'm curious to see how it works out.

Swap the spark plug and ignition coil from #5 to another cylinder.
Clear codes & run, then check codes again. GL

update
 

The marked numbers are how they sat in line before i moved them(orginal stock positions). The reason its 3, 5, then 4 is because initially when i received the first p0305 i switched 4 and 5. Then i got the p0305 again, so i switched 3 with 5, giving me this result.
Attachment 12152Ok Here's what I did;
Switched coil pack 5 with three, and also inspected and reinstalled the 5th spark plug. Appeared fine. Also checked the wiring to plug 5, seemed fine.

Attachment 12154
Notice how dirty coil pack 3 is.

Attachment 12156
Where coil pack 5 sits, looks clean.
Attachment 12158
Coil pack 5, much cleaner than 3. Odd!
Attachment 12160
Spark plug 5. No damage, seems clean.

So that's where i'm at so far.
Next guess is a bad fuel injector?

During the run, use a mechanics stethoscope to "listen" to the injector comparing #5 to the rest of the injectors. GL

Hummer z; i didnt exchange the spark plug. I'll clear codes and swap them tomorrow, see if that changes anything.