Random misfire at Idle, no codes yet

[H32NV]

Just when she's all back together from winter projects and running like a champ on the last few trails that I ran, I went to start the H3 this morning, and its all of a sudden got a random misfire at idle. It's pretty mild, and doesnt effect vehicle operation, and hasnt thrown a code yet, but I did replace the Intake Cam Position Sensor about 10,000 miles ago. Maybe its the crank?. 99.3k miles. dangerously close to warranty. any ideas?

 

[Big2dabank]

Fouled plug???

 

[alrock]

Slightly off topic but I'm about to replace the two Camshaft position sensors. Intake is which location? How easy of a job is it?

MAF could be a culprit though usually that throws a code pretty quickly. I've also heard others talk about double checking wiring and connectors when replacing the Camshaft Position Sensors - make sure there's not an intermittent issue there with frayed, exposed or loose wiring.

 

[H32NV]

the intake one is super easy. its on the frontside of the engine block and bolts on with one 12mm bolt if I remember correctly. There's also a cam position sensor actuator? that was replaced about 15,000 miles ago, its the sideways silver can/plug looking one on the left side-top of the engine near the front. I cleaned my MAF about 6,000 miles ago, although thats a good idea to look at it again...

Also, all new plugs 10k miles ago. OEM platinums/iridium, whatever it was from the factory.

 

[alrock]

It doesn't take long for my MAF to get wisps of dirt on them, regardless of the filter I use. I think it squeezes between the filter and the housing (round filter from 06-07). I hope you get a code if just to help pinpoint issues. Well, I hope it goes away first and doesn't reappear, but if it does then hopefully the codes show. You could have a coil on its way out too.

 

[H3slate]

I had a similar issue that finally posted a code of p0302. Thought it was the cylinder head, but replaced the ignition coil and it runs great now.

I could feel and hear the miss at idle, but under load the engine ran fine.

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[H32NV]

Also, just today I came home to "the letter" that everyone has been talking about. Un-related to this thread, but I was offered $1100 over book price for the vehicle in good condition. Does that seem comparable to others who have been contacted by their dealerships?

 

[06 H3]

Check the plugs then the ignition coil then head. I did the plugs first kept pulling P0302 then replaced the coil still pulled the code then replaced the head...

 

[H32NV]

well ive got 500 miles left on my warranty, I'm at 99,500mi. I havent thrown a code yet... are ignition coils covered under powertrain? Or should I just go and replace it myself and see if that fixes it? if not then take it in...

 

[alrock]

Powertrain coverage varies by year but I'm pretty sure these aren't covered.

 

[H3slate]

While dealing with the misfire I was able to pull a "pending" code for the misfire. So it registered that it happened, just not enough to trigger the cel light.

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[H32NV]

Am I reading this right on AutoZone, that an ignition coil is $109 each, and should I be replacing all 5? thats a bit spendy. What is the best way to check them? other than look for the arc

 

[H3slate]

I got mine from amazon for a lot less than that. You can check the coil by switching it with another one. I did this, engine ran even worse than before.

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[H32NV]

they appear to be $22 on gmpartsdirect. that seems to be more palatable. Maybe I should just replace all 5.

 

[06 H3]

Wait before you do check them and see if they look like this!!

this one is good the top one is bad.

 

[evldave]

they appear to be $22 on gmpartsdirect. that seems to be more palatable. Maybe I should just replace all 5.

I paid $35 at a local parts house, just replaced the one bad coil (I switch them around to make sure it was the coil)...I bought an extra just in case another went out, but there's no need to replace them all at the same time.

 

[bebe]

Run a couple of bottles/tanks of injector cleaner through first!