I got my head gaskets done on my 2007 Explorer Sport Trac 4.0 SOHC in December. When I got my truck back the PCM was blown so I replaced that. Now the truck runs real rough. No codes are coming up. I pulled each plug wire from the coil block and it seem like cylinder 5 and 6 are dead. I am getting spark on all. The plugs on all cylinders look white (lean ???). I checked the compression on 5 and 6 and its low. Does this mean bad head or piston rings?
Could it be injectors or something else? The long term fuel trim is 20.

 

Update:

Cylinder 1 180 psi
Cylinder 2 Not tested
Cylinder 3 Not tested
Cylinder 4 180 psi
Cylinder 5 60 psi
Cylinder 6 35 psi

 

Replacing the PCM, did you just plug the new one in, or did you do anything else to help the PCM learn the new engine. I know with GM's, you need to do a CASE relearn in order for the PCM to understand where TDC is. Your long term fuel trims mean that the engine is running lean if that is a positive number....it means it's adding 20 percent fuel to what it perceives as a lean condition. You might want to contact the dealer and see if they need to do any programming on the new PCM in order for your truck to run correctly. They aren't just plug and play...

 

Also, if the PCM was blown, did you figure out why it had gone bad? Moisture, bad ground, voltage spike? If there was a problem with voltage or ground to the old PCM causing it to fail, it might be affecting the new one until it finally gives up the ghost. The computers in modern cars are pretty robust, but they are still razor thin contacts and circuitry mounted to a fiberglass board.

 

Oh, yikes...did you just replace the head gaskets and not have the heads tested? Gaskets rarely fail unless through corrosion, and even then, the corrosion that affected the gasket will likely affect the head as well. My Guess is that the original failure was between 5 and 6? If that's the case, then that head needs to come back off and get resurfaced/magnafluxed/checked for cracks.

 

The heads were resurfaced but I don't think they were tested for cracks. It was 5 and 6 where the gasket went btw. Why do I not see antifreeze in my oil this time if the heads cracked?

 

Who did the work?

Did you change out the tensioners and guides?

No codes?

Lean might point to vacuum leaks. These engines are prone to intake o-ring leaks and intake cracking.

 

I guess at this point I would do a leak down test on 5 and 6. There exists the possibility of ring fouling from the antifreeze leak.

 

Is it possible that the cam timing is of to cause low compression on 2 cylinders?

 

No. All cylinders would be affected. And you might have bent valves in all cylinders. Whoever did the work on this engine should be figuring this out.