I had another thread created so I'm going to copy and paste to save me a ton of time.

I've had it up to about here with this truck. 5.4 V8 year 2000. I don't know what else to do. CEL came on for 5 & 8, brought it in to the mechanic since it's 10* outside, they did all the cylinders COPs and spark plugs which I provided. Motorcraft SPs, and COPs.

Take it home, still running rough, symptoms of a bad fuel filter. So I replaced that just now. Go to start it up, CEL back on and cylinder 8 misfiring again. It's running rough and I'm honestly fed up. It holds back on me from 45-50mph. Right when OD kicks in it holds back and the engine shakes.

CEL for 8 misfiring 3 times in the past 2 months. 2 in the past week. I've replaced the SP and COP. Checked fuel line pressure, comes up fine. PCV valve is fine, valve in the back that 90* elbow that always pinches is fine, cleaned the TB, and just did a pressure check and here's the results:

Cyl 1: 195psi
Cyl 2: 97psi
Cyl 3: 135psi
Cyl 4: 95psi
Cyl 5: 190psi
Cyl 6: 175psi
Cyl 7: 133psi
Cyl 8: 185psi

A few things to note, throttle was fully opened, and did 5 full cranks of the motor.


So far on cyl 2 & 3 testing with oil resulted this:
2: without oil was 97psi with oil 130 psi
3: without oil was 135psi with oil 150psi

So now what? What is there left to do other than to rip into the motor? Add some MMO and pray? Sticky exhaust valve? What do you think?

 

Have you tried swapping the offending cylinder's injector with a good cylinder to see if the problem moves or stays put?

 

All new fuel injectors. All are injecting perfectly.

 

Quote:

Originally Posted by Titus136

I had another thread created so I'm going to copy and paste to save me a ton of time.

I believe that a "Leak Down Test" is your best hope in identifying the problem with these cylinders. The test will tell you or your mechanic wether the valves or rings are the problem in the low cylinders of which you have 4. #1,3,4, & 7 and it might be that for some reason your cams jumped time.

 

Also I'm having a skip issue, what would be causing that?

My mechanic has it now due to me simply on the verge of driving the damn thing off a cliff.

 

I belive you should address the major issue; low compression, first identify the cause of that and then either fix it or trade it.