After 222,000 miles my 3VZE is finally giving up on me. #6 cylinder has about 90 psi of compression.

So, I really want to do a 3.4 swap but I am in CA and the passenger side drop issue scares me a bit. Plus I just put $600 in parts on the front of the motor last week. All OEM timing parts, belts and hoses. Which in hindsight was dumb.

So......decisions decisions.

Anyone have experience driving for awhile on a motor that has such low compression on one cylinder? I am not sure what the ramifications are.

Number six you say? Check for a blown head gasket. The low compression won't hurt much but you can limp it around for a bit, but if the low compression is due to a blown or blowing head gasket, you don't really want to drive it around. When that thing finally lets go it'll strand you. Find out what's causing the low compression post haste, and then go from there.

Don't be scared of the 3.4 swap. The 3.4 Tacomas and 4Runners may be drivers drop, but even if you don't reuse your existing transmission, you can source a tcase from a 3.4 T100 or an earlier A340F trans that are both passenger drop.

I don't think the head gasket is blown. The oil and coolant both look good. The thing runs fine and seems to run the same as it has the last couple years. I just noticed its been idling rough lately.

I have a manual tranny which I plan on keeping(had tranny and transfer case gone thru last year), so i know that I will have to do a drivers side drop. I don't really want to go thru the hassle of doing a passenger side drop, getting it thru the ref., then changeing it. The A340f is a auto right?

I have a feeling this cylinder has been weak for a long time.

I too was in your position. The California emissions standards are tough. I can highly recommend a engine re builder in Ontario California that did my engine and installation for under $ 1900. Been going strong for fours years and two smog checks. On ski trips to Mammoth I average 18 MPG going up and 21 MPG coming down the 395. My 3.0 does just find.
PM me if you need contact information

Willy, that seems really reasonable. My local shop wants $3000. How Many miles have you put on the motor?

My reman 3.0 long block cost me 2700 & get the rest of the gaskets that arnt included in a complete motor gasket kit + I have to do all the work.....

If you can get the whole thing done right for $1900 (not just a half assed rebuild) Id jump on that like a hobo on a Hot Dog!

I have driven 40,000 since the the rebuild was put in. My 3.0 also has have the injectors replaced and the water pump bracket replaced . 2 1/4 inch new exhaust and cat were done this helped with the mileage and power. Also a three row aluminum radiator.
Considering what a newer less capable 4runner will cost these repairs are cheap.

Willy, PM sent.

I finally got around to doing a leakdown test. #6 cylinder has a bad exhaust valve. It is reading about 30% more leakage than the two other cylinders I tested. You can hear quite a bit of air coming out the exhaust. I was going to do them all but it really doesn't matter at this point what they show. The engine is going to get replaced or rebuilt.

Sounds like you found the problem.

But just wanted to say that a head gasket failure doesn't always result in oil or coolant looking bad. It depends on the failure. You can also have oil or coolant making it's way out of the engine or into the combustion chamber.

I believe the friend's 3000gt that he gave me had both of these problems, yet the coolant and oil looked fine and very little was lost. But some (and then more) oil was making it out the front of the engine and then smoking once up to temp. And it failed CA tailpipe smog, likely from one or both getting into the combustion (and also causing O2 sensors to foul). And this engine had bad compression in one cylinder, along with occasionally a terrible sound.

Good luck on your fix.

Wouldn't it be cheaper to do a valve job? @KidVermicious - what do you think?

This whole post kind of scares me, as I have 1 cylinder testing pretty low relative to the other 5 on my 3.4

compression test question

Depends on what you mean by valve job. That normally means pulling the heads, stripping them down, and putting all new valve stems and assorted goodies in. If he's going to pull the heads, he might as well pull the motor and rebuild the whole thing. If you're talking about a valve adjustment, that's a different thing. You can certainly adjust the valves without pulling and rebuilding/replacing the entire motor, but I don't think that'll help him in this case. I'm not a trained mechanic, but I think the results of his leakdown test rule out a bad adjustment.

In your case, bad compression on one cylinder could be a lot of things - it could be a bad head gasket, it could be a bad valve (probably exhaust, but an intake valve is possible), it could be worn piston rings or cylinder wall damage, etc. You've got some more isolation to do before you can point the finger at any one cause. If it does turn out to be a valve issue, it's not likely that adjusting the valve shim thickness will cure it - that shim would have to be STUPIDLY out of spec to cause a loss of compression in the cylinder.