I just picked up a clean 88 Extracab with a 3.0 with a 5 speed and 214k miles . The previous owner was selling it because it would no longer pass emissions and had low compression in two cylinders. My plan is to do a 3.4 swap and eventually a SAS. However, I'm wondering if it is worth trying to adjust the valves on the 3.0 to see if that will fix the problem and let me drive it as-is for awhile as the engine looks to be in good condition with a recently replaced timing belt, alternator, power steering pump, etc.

The engine has no compression in cylinders #1 and #3 according to a compression test the previous owner had a mechanic do. The truck starts up and idles normal, but driving the truck it certainly feels like it is only running on 4 cylinders. I'm assuming it is the exhaust valves being out of adjustment as there is no signs of the head gasket being bad. Is it possible that the valves are just out of adjustment or are they likely already burnt? Anyone had any luck with adjusting valves to fix compression on the 3.0?

 

If the valves are the cause of the low compression adjusting them might do something. Unless they are bent.
If your already eyeing a 3.4 to swap in, don't bother trying to save the 3.0 and go straight to the 3.4 that's just my opinion.

 

You reasonably easily check the valve clearance. You'll have to pull the intake mani to do both sides. You can loosen the cam bolts enough to swap shims around with a good magnet. Sometimes you'll get lucky and will be able to swap shims enough to get them close. Other times you'll have to get a few from Toyota.

 

Did you ever figure it out? Have the same thing going on. Thanks!

 

Pop your valve covers off and see if you have any clearance on intake and exhaust valves in the problem cylinders. There's no universal answer for low compression.

 

probably blew the gasket out between the cylinders 1 and 3. 0 compression and not even a little points to this. if it were burned valves leaking that bad you would hear it "chugging" in the exhaust note.

 

Yes, you should check the valve clearance before doing anything major.

BUT: if the clearance on an exhaust valve got so low the valve wasn't closing, it also means the valve wasn't getting cooled and will rapidly burn up. By the time it gets to "zero" compression you probably need to replace a valve.

 

I had this exact same thing happen to me. I had zero clearance on two cylinders exhaust valves. I had nearly zero compression on those two cylinders. Unfortunately not having proper clearance caused the valves to stay open and burn up. Had to replace them. Hope this helps.

 

I know this thread has been open for a bit. If your planing to swap to a 3.4 I would just wait for that. Otherwise, if you do want to mess with the valves and heads, I would just do a rebuild from the heads up (machine shop to clean, Xray replace parts, new Valve cover gasket, half moons, ect..). Will most likely be about 1600 to 1800 for everything and It could fix your compression.

However, worn piston rings can also cause low or no compression as well. At that point you may just want to swap to the 3.4.

 

Do a cylinder leak down test.

 

Sorry novice here but having a poor, sloppy engine when cold or ambient is cool/Humid ( mostly just when engine is not yet reached operating temp). First thoughts are: O2 censor or plugged up Cat. This was a junkyard rebuilt engine swap because the previous on developed some knocking when going up a pretty steep pass and gave out. Rods blew out the engine. Have a feeling that engine was running rich or valves were bent or out of adjustment. Thoughts? And what is a leak down test I have never heard of that..

Thanks in advance
Josh

95 4Runner 3.0 4wd 4 Door Standard

 

did you ever figure out what the problem was? I'm in the same situation and I am stumped