Huckm80

Hello all,

This is my first post on the site. I've got a '95 pickup V6 that been running rough at idle and throwing a lean engine code (for longer than I care to admit). The truck still has decent power and gets 16mpg.

My 3vze has 188,000 on it and #6 cylinder has almost zero compression while all the others are around 160psi. I checked the valve clearance on #6 exh valve and there was NO measurable clearance. I swapped the 2.9mm shim with a 2.75mm shim (.006 smaller) and still there was no clearance that was measurable.

My question is: Is it possible that the valve is WAY out of adjustment (needing a smaller shim) or is this a sure sign of a burnt valve? Is there any hope a different shim will bring the compression back?

Thanks for any help!

TNRabbit

Could be burned/stuck open if it's been that way for a while. The only way to know for sure is to pull the head. If compression is at zero & you're still getting 16 mpg, you're one lucky SOB~

More details about the engine/truck would be helpful. It's easiest to just add it to your signature so it's always there (year/model/engine/tranny/4wd/etc.).

skypilot

iTrader: (1)

Sounds like its beyond burnt, maybe its just trying to pop out of the head & you have a nice hole in the piston too.

nerdlip

I just finished adjusting the valves on my 3vze a few hours ago. Mine had never been adjusted in the 280,000 miles i have had the truck. The initial readings were as follows: #1@160psi, #2@155psi, #3@160psi, #4@90psi, #5@160psi and #6@130psi. The clearance for all intake valves were spot on @.010in. The exhaust valve clearances were another story with #1@.004 ,#2@.007, #3@.005, #4@0(no clearance at all), #5@.006 and #6@.005. I found the chart in the factory manual to be pretty helpful for finding the correct replacement shim thickness except for the one that had zero clearance. I had to first order the size the chart suggested then after i had actual measurable clearance i had to order a thinner shim to get the correct gap. So after all exhaust valves were shimmed to the factory specs between .009-.013in i have the following results: #1@165psi, #2@170psi, #3@170psi, #4@110psi, #5@170psi, #6@170psi. I obviously still have an issue with my #4 cylinder compression which i suppose is a burnt valve from having zero clearance for too long. That will be worked on later. I just wanted to show everyone that MOST of the compression numbers did improve after adjusting the valve clearance within spec. Even with the #4 cylinder that low the engine runs much better than before. All compression test were done with engine warm.

4wd4fun

what wre the intake clearances? that can have a lot to do with compression too.
i'd hate to think you went thru that and still have a prob with the intakes.
nevermind- i see you said there on

Huckm80

Nice work Nerdlip! I bet she runs like a deer in hunting season now! I ordered a 2.3 and 2.4mm shim for my #6 exhaust valve (educated guess). Turns out the 2.3 mm shim gave me exactly .013" clearance. With the old shim the valve had -.011" clearance. My compression went from zero to 75psi! I am going to check it again soon after driving it for a few weeks to see if there is any change. I can't imagine having to check the valve lash every 30k miles like the book says.

DBS

My 4runner had a CEL with a misfire code. It ran fine except for occasionally stalling at idle particularly when the engine was hot. Dealer reported that the compression in cylinder #2 was 135 psi. Recommended a $4,000 head job. I took it home and adjusted the valves the compression came up to 174, nearly at spec. Don't hesitate to question dealer diagnosis. 2.7 liter engine with 211K.

"G"

2.7 liter engine?

rworegon

What is the question???? Yes, the 3rz-fe is a 2.7L engine used in various Toyota products.