Cracked head at cyl #3 at only 37K mi. It's out of warranty so a local shop with a very good rep replaced the head. They had some problem setting timing until they found the TSB on timing belt. BUT, now it has a flashing CEL, code is mis-fire cyl #4 - lean (not the replaced head, the other side they didn't touch). Also Random Mis-fire code at times.

They reset the timing belt numerous times, swapped plug, coil,and even injector between cylinders but error stays at #4. FWIW the compression on #4 is 10# lower than the other 5, but w/in spec.

They're at their wits end, anyone have an idea ?

Thanks.

BTW,it didn't have this problem before it when into the shop.

If the ecm has stored a hard code, then it needs to be reset correctly to clear the light and relearn the fault.
Since your truck is obdII I'm not sure a generic scanner can completly reset the comp. correctly enough to let the ecm resume learning.... this may not matter but just a thought