Need help with check engine light code 25. Does anyone have an idea or where to start with this? I looked it up but couldn't find much other then it may be running lean and it does smell like fuel. Not sure what or how to fix that. Just recently got the truck 91 4runner v6 4x4. I just did spark plugs, cap and rotor, oxygen sensor, timing belt/water pump, and pcv valve. Light was on before I did that stuff. Any help thanks

 

Did you clear the codes after you installed the new parts?

My guess would be the 02 sensor, but you already replaced that.

Check for any leaks in the intake. They like to hide in the bends of the tubing, hold them up the light and bend them, if light shines through cracks, replace it.

Good trouble shooting code 25 thread.

https://www.yotatech.com/forums/f116...-3vz-e-258926/

 

Well when I tried clearing it by removing the fuse it wouldn't clear...but since I recently did my timing I had my battery disconnectded for few days and that cleared it up for a bit. After few times driving it came back on. I have not checked the intake I will do that. Do you think the catalytic or exhaust would have anything to do with it? My muffler does have few holes in it and not sure if the cat is good.

 

I dont think so. Your stock exhaust manifold makes all the back pressure your engine needs.

 

Okay so I think I found an issue.. The truck has been running pretty shaky and sluggish. I did a compression test and cylinder number one read 30psi with it just cranking and 60 psi running. All other cyclinders read from 149-150psi. What does this mean in the sense of work to be done or what can it be.

Thanks

 

What does the oil look like? Milky? It sound like you probably have a blown head gasket. Might be something else but probably not.

 

No not really.I just did an oil change and didn't look strange. It doesn't over heat. There aren't any visible leaks from the head area.

 

I suggest a leak-down test. That will pinpoint: head gasket, intake valve, exhaust valve or rings as the failure.


But if I had to guess, since you say you're oil looked fine, head gasket and rings are probably out leaving bent, stuck or mal-adjusted valve(s).


Can't rule out cracked head or block though... but those would probably show up as contamination in the oil or coolant, i.e. gasoline in the oil or coolant.

 

I was doing some reading on the compression test and people are saying to remove all spark plugs and hold throttle fully open? Is this necessary to get a good compression reading?. I checked compression with all other spark plugs in and not holding the throttle open.

 

You'll get the most accuracy on the compression test with plugs out and throttle open, but no matter how you do the test it won't change a 30 psi reading to 150 psi. I agree the most likely problem is a bad exhaust valve. Pull the valve cover and check the valve clearances. If that cylinder is at zero clearance it's another indication that could be the problem.

 

Okay I'll try removing removing that valve cover again. I just removed it like two days ago to do the seal and didn't check the valves :/ sucks. Can that cause error code 25? Lean condition.

 

Either way you need to trouble shoot the bad hole before I would even continue worrying about the trouble code. Which cylinder has low compression? A burnt exhaust valve is probably the most common cause of that on the 3vze.

 

Its on Cylinder 1

 

Anthing special needed to check valve clearance/adjustment?

 

As with anything else you're doing, you need to start with The Good Book:
http://personal.utulsa.edu/~nathan-b...e/64tuneup.pdf (page 19).

Checking the clearance is pretty straight-forward, adjusting not so much. You need to replace shims (my dealer had some, and my machine shop had the set), and to do that you will need a tool like this: (others have managed to do it with just a small screwdriver, but that's beyond my skill set).

In your case, you may be looking for an exhaust valve with "zero" clearance. If you have one, there's a good chance it's already burned and adjusting it won't help. Of course, adjusting it is actually pretty easy compared to removing the head to replace a valve, so you're likely to want to try it. But if there is "no" clearance, you won't be able to tell how far off it is, and you might be guessing on the shim size.

Good luck!

 

How do I perform a leak down test? Where do I start to pin point this problem.thanks

 

Thanks this is very helpful

 

Could easily be a simple vacuum leak.

My roommate likes to use carb cleaner, but propane is a lot safer

 

Nice I will try that leak test and see what happens..