I have a 91 pickup 3vze 4x4. My truck has been having a very rough idle lately, and I've determined that it is the number 3 cylinder. I am getting spark to the plug, however, when i remove the wire from the distributor there is no change in the way the truck runs. I have been researching on this site for the past few weeks trying to find a solution. I am getting codes 25 and 26. All of this seemed to happen after i seafoamed my truck. I have seafoamed it many times without a problem, but this time is different.

here are the readings from a compression test.
cyl 1: 170
cyl 2: 160
cyl 3: 100 (poured oil in spark plug hole, retested, and got 160)
cyl 4: 170
cyl 5: 170
cyl 6: 165


are my piston rings to blame? if so, why did it happen only after the seafoam?
the problem is only noticeable during idle. I probably have a lack of power, but the 3.0 has always been slow for me so i haven't really noticed too much of a change.

what is going on with my truck?

 

i had about the same problem it turned out to be #3 and #5 valves burnt. from the vacume
valve on the bottom of the ps pump sucking all the ATF in the intake.

 

The weird thing is that it only started after the seafoam...
How do I test for exhaust valves being burnt?

 

Could egr have anything to do with it?

 

try a pressure gage test to check it its making a good seal...

 

how do i do that?
can i rent the tool from autozone?

 

you can buy a compression test tool from IE, Sears, but i perfer you to try harbor freight tools its a dirt cheap way to buy tools you will only use once or tiwce in a life time.. snap on or anything else you are just wasting your moneying if your not using it everyday...

 

You've already tested the valve seal, if the valves were bad, you would have still had bad compression after adding oil to the cylinder and re-testing. The fact that your compression went up to 160 after adding oil indicates you have bad rings on that cylinder. The seafoam treatment MAY have broke loose the crud that was holding the last bits of your rings in place but most likely coincidental.

Sounds like its time for a rebuild, sorry.

 

u could just add 2 QUARTS OF 90W