2006 with 2.4, 98,000 miles, I have a randomly occurring miss that triggers a cylinder 4 misfire code-sometimes. Starts good cold, runs great (new plugs, coils, #4 injector, lots of Lucas FI cleaner since I bought it 2,000 miles ago), and gets good mileage, etc. But, upon restart after a say 30 minute stop, it may or may not, miss and throw a code. If I kill it and restart it is fine. Is this a computer issue? It may go a couple hundred miles and a week or so between events. Have not checked compression but doubt it would be the problem as the truck has had regular maintenance. I'm the second owner.

 

What does "regular maintenance" have to do with compression?
What is the code number? Any other codes?
Did you use ACDelco 41-103 plugs?
is coolant or oil disappearing?
What color were the removed plugs?
Have you checked all of the wires and connectors to the engine sensors and solenoids?
Have you looked at the timing chain?

Misfires are detected by variations in the crankshaft speed. Has the crankshaft sensor or ECM been replaced? If it has it needs to be relearned. They frequently get replaced by misguided interpretation of P0016/P0017.

 

Check the wire harness?

 

Swap the coil with neighbor. Did misfire move?

 

Is it possible you put the wrong fuel injector in #4? Have you tried cleaning the fuel rail? What spark plugs did you use?

 

I'll take cleaning the fuel rail for $400, Alex.

 

Faulty wire connection in #4 injector, for $600

 

Plugs were ok, but #4 was a little darker than other three; no head gasket issues; no compression check; have not swapped coils; used same number plugs that came out of it; used correct injector. Uses no oil, loses no coolant. Gets 22/29 MPG; Thanks to all.

 

Code was Po3040 or something like that, for #4. It shows it missing while running on a scanner. From a 2 to an 8 occasionally a 12. Lately, it hasn't thrown a check engine light, just the traction control and it goes away on restart.

 

Same that came out does not mean the correct ACDelco 41-103.. What does "From a 2 to an 8 occasionally a 12." mean? Code numbers are important, the name that a scanner gives to the test don't mean what you think.

So now you are saying no CEL? How do you know it is misfiring? P0340 means something entirely different from P0304 either can turn the ESC/TC off