I've run into the egr problem before on other vehicles....but this truck doesnt have one...it was one of the first things I looked for.

When I do the compresiion test today I will unplug the coil...and I'm supposing I should pull the power to the fuel pump as well?

If the plenum is the issue would this explain some of the popping back thru the throttle body that I heard when I was revving by hand under the hood?
It was only mildly noticeable...nothing major...only heard it with the air cleaner off and my head under the hood....just curious.
I should have more to report back this evening...gotta go run some tests...then I'm goin fishin to relax............or maybe get even more frustrated!!LOL

 

Yep. Need to disable the fuel pump as well.

Not sure if the plenum will cause it to backfire, but, I don't think it would...... that sounds like more of a timing/valve issue......

 

well heres what I got on the compression test

cyl #
1 120
3 138
5 18
7 100
2 115
4 8
6 30
8 10

I rechecked the numbers 2-3 times each cylinder
cranked the engine for 10 seconds each test
tried cylinder 6 the third time with a little oil shot down the cylinder..ende up with 35psi....the numbers were so low on the other cylinders I didnt bother with the oil test.
stuck valves?
bad cam?

 

Probably bad valves. Possibly bad rings.... doing the wet test anyway might be a good idea, if the numbers don't come up much, then you are looking at pulling the heads. For the cost of having the heads checked out, and then repaired (if they aren't trashed to begin with....) you could just as easily pick up a pair of NEW heads from Clearwater Cylinder Head. They sell BETTER heads on EBay, for 270 each. They are better designs than the factory head, have thicker decks, so are less prone to cracking like the factory units.

If the numbers jump pretty good on the wet test though.... it is gonna be rebuild time. Or, just replace the motor.

 

Do the wet test and see if the numbers come up.
If they dont try pulling valve cover and squirt Marvel Mysterey oil on the valve stems of the low compression cylinders.
It may take some time to free them up but it will.
While valve covers are off crank it over and see if all valves are moving.

Dave

 

thanks for the help so far guys...I REALLY appreciate it!!
will re-run the tests tommorrow...dry and wet...then pull the valve covers and look it over.

 

I want to also add that...this truck seemed to run good last year when it was parked...but its been setting for nearly a year now...you suppose that was enough to stick the valves?

 

Entirely possible.

 

re-ran the test today....4 squirts oil down each of the troubled cylinders,no change except cylinder 6 went from 30...60psi.
pulled passenger side valve cover...all looked normal...started the truck let it run for about ten minutes after soaking it with pb blaster....no effect.

sounds like I'm pulling a motor...if you have to rip 3/4 of it apart ...might as well re gasket the leaky oild pan etc,..

anybody know what the differences between model years is for the engines?

local salvage yard is getting $850-900 fo good running engines ..they have '99-01 years to select from...are ther any compatability issues to expect?
what if I went 5.2 vs staying 5.9?

 

The basic engine is all the same. Some minor differences in intake manifolds thru the years, and the fuel rail. If you reuse your parts, shouldn't be a problem.

For the money...... you might want to spend a few hundred more, and get a Rebuilt motor. Or, as it seems that your rings are pretty much ok, the one cylinder aside.... just replacing your heads would be relatively cheaper. You could even re-ring the entire engine and still have less into it than a junkyard motor. (that still has all the weak points of what you are replacing....) Toss in some new bearings, and you HAVE a rebuilt motor...... and you know what ya got. The junkyard motor is a crap shoot. I bought a 'good running' motor..... only to have it develop a rod knock within a week of installation. I was not a happy camper.

If you change to a 5.2, you will need to reflash the computer as well, to clue it in about the smaller motor.