Well I have been having trouble with this truck for awhile now. I went out today and did some real troubleshooting and thinking and think it may be a bad valve.

Here is what I have now:

1. Engine runs rough at idle, but ok at highway speeds.
2. After a 15 minute warmup at idle the forward O2 sensor on bank #2 steadily climbs to about .775v and does not fluctuate, indicating a steady RICH condition.
3. During the same time the #2 bank long and short term fuel trims go steadily lean.
4. If you hold an index card over the exhaust pipe it will get sucked down to the pipe intermittently.
5. Cyl 5, which is on bank #2 has slightly lower compression than the rest of the cylinders.
6. Engine idle drifts up and down through a range of about 50 RPM's.


To me this is screaming "BAD VALVE".

What do you guys think????? Could it be anything else?

 

It sounds like a valve is sticking. Everything you did sounds tight and points to cylinder head issues