So it was a high mileage truck , started missing on cylinder 5 and then eventually po300. So I did the usual stuff copper 570 plugs , wires , then tried new coils , injectors and still skipping. So I did a compression test and #5 was only 50 psi , #8 was worse. So I pulled it and did a full rebuild. It's still skipping ....... So I also replaced the cam and crank sensors , as well as the egr valve. My fuel pressure was 60psi so I'm not thinking it's a fuel delivery problem ? The throttle body was cleaned when I did the plugs as well. Since the rebuild I again replaced the plugs , this is where I'm at a loss. Cylinders 2 and 6 had dirty plugs as well as 1 and 5. I did pull the injection/coil harness to inspect it , all looked good. The truck idles a little rough and it misses to the point of shaking under light load or cruising , the truck has an audible miss at higher rpms. I have tried resetting the pcm , pulling the wires overnight and touching them together etc. What am I missing ?

 

Have any work done on the heads?

 

Yes I disassembled them and sent them with the block to get checked and washed. They cut .011 to square them up , and then I reassembled them with new seals and replacement springs. I used dye-chem to check the valves have good a seal to the seats.

 

Ok. That sounds pretty thorough.

Think I might run another compression test, and see where the numbers are at. (or, if you have the right weapons, cylinder leakdown test.)

 

Compression test was 170-175 across the board , I double checked the timing as well as verification of full cam lift at each valve. It's a non mds motor

 

Ok, so much for that thought.

I know your injectors are new, but, try swapping the injector from one of the cylinders you are getting a code from, to a cylinder you are NOT getting a code from. See if the miss follows the injector.

 

I'm waiting on a injector pulse test tool in the mail now , should be here today. But yes I was considering that too. Thanks for the info.

 

Let us know what you find out.

 

So it turns out that 4 of the " new " injectors were in fact faulty. I performed a injector flow rate test and two were intermittently malfunctioning and two others were not within accepted parameters . So I dug the old ones out of the bottom of the old parts box and cleaned them cleaned them out and installed them with new screens and I rings . Now it's running fine and no more codes !

 

Yeah, wouldn't be the first time I have gotten bad parts, right out of the box.....

At least its fixed.