Trouble shoot Cold miss for 2 blocks
 

I have very slight miss or surging from a cold start but only discernable
for 2 blocks. If it is still there after reaching normal operating temperature I can't feel it. There is no fluctuation on the tach (not very sensitive),I don't feel a lose of power but sometimes there is a slight delay in trottle response. I always have the AT in manual so it is in 3rd. gear at about 2000rpms. No codes show on my Bavauto Peake equivalent scanner. I am leaning toward an O2 sensor because the milage seems to have dropped offbut as you know it could be one of several other or a combination of possible causes. I don't want keep driving until it gets worse as I am concerned about ruining a cat. 108,000 on the engine. Question is---how do I determine the cause without throwing parts at it. I am kindaOK paying the dealer to diagnose the problem.. Can I get the information with an onboard unlock?

I had the exact same symptoms. Eventually I got a CEL for a misfire on cyl 6. I swapped the ignition coil to cyl 5, cleared codes, started it up, got a CEL for misfire cyl 5. This led me to believe it was the ignition coil. Replaced coil. No misfire since.

The misfire started in the cold weather, just like yours. Unfortunately I did not get a CEL for over 2 months. Finally when I got on the throttle hard, the CEL came on and I was able to get the code.

I have an extra coil, I can ship it to you, the bad news is that you'd have to swap it on each cylinder to troubleshoot.

Thanks for the coil offer.

It isn't cold weather, it is just the first start in the morning when the engine is cold. I have thought about a coil as it has the original coils. I can check them with a stethoscope as a bad one will sound different. I haven't because as far as I can tell it goes away after the engine has been running for 3-4 minutes.

I have tried the hard throttle-so far no code. What reader are you using?

I see we have similar rides, I went Dinan shortly after I purchased mine new.

My coil must have gone south fast, one day it was a slight misfire and the next week it was missing BADLY. If you aren't throwing a code yet, and your coil is starting to fail, my experience shows that you'll get the CEL sooner rather than later. It started with a CEL flash, then I hammered on it... solid CEL from there on out.

When you first start it, run to the back of the car and you might notice the misfire on one side or the other. My drivers side bank was clearly missing. That would at least narrow it down to 4 coils instead of 8.

I used the Peake scan tool.

Yes, we do have similar trucks. Mine was also Dinan modified as it left the dealership.

I will try that tomorrow morning. It is so slight it is hard to feel without a load on the engine. I will have my wife put it in drive and hold it with the brake and see if I can tell which bank. CEL hasn't even flashed and this has been going on for month or more. I haven't reset the MPG monitor for a long time. I checked it yesterday and it was showing 12. Usually it is a little over 15. I reset it and will check that when I have run half a tank through. Once in a while if I rev it shortly after a cold start I will get a small pop from the passenger side exhaust which would indicate a rich condition. I haven't been able to make it happen after it is up to temperature. I have checked the vacuum lines, air filter, MAF, and throttle body so it appears to be downstream from those.

I just started it up and held a sheet of paper over the exhaust on each side. It is clearly the drivers side. Can't hear it but can see that bank is not a steady rhythm.