My buddy swapped an 04 LQ4 into his 00 Sierra about three weeks ago. The last few days, it has began to misfire. We assume its either an injector, coil pack, spark plug or wire because its only two cylinders misfiring. He was wanting to possibly swap out an injector from his 00 4.8 into the 6.0 to see if there was something wrong with the 6.0 injector. Are they the same size or are they different? TIA

 

No difference. They are both 24.7#. Try swapping coils, check for a BROKEN injector wire right at the plug. It can happen and it did on my 99 when I swapped. I looked and looked for the miss. Finally found a single small wire broke loose from the contact at one injector.

 

thanks jared! he's coming over after work tonight. we're planning on swapping his old coil packs back on, he already has new plugs, we were going to try a different injector, and a new plug wire while we were at it. hopefully we'll get it cleared up! thanks again!

 

update:

after swapping coils, plugs, wires, and the injectors, the truck still continues to misfire. note that the misfire is only on cylinder 1 and 5. he had the truck hooked up to a machine and none of the other cylinders were misfiring. the number 1 cylinder fluctuated from 5 misfires to 16 misfires. what would you suggest he do next? is it a possibility that its a tuning problem since he's replaced the 'mechanical' parts?