2TR-FE 2006 255k Misfire on Three and Zero Compression

I'm working through a problem with an 06 Tacoma 4cyl with 250k miles. On a long run yesterday it threw a code for Misfire on cylinder three. It got home but is idling rough and the code is still present after a reset.

So far I have replaced plugs and swapped the coils with no change.

The plugs I removed were normal except for three which was black.

I tested the compression, which was 150psi in every cylinder but three, which was zero. The gauge doesn't even wobble. I tried five times, just in case the guage wasnt seating, I suppose it still could be that, but the same procedure on all the other cylinders gave decent results.

I have put a camera into the cylinder and there are carbon deposits and a bit of lose granular carbon in all of the cylinders. Three is wet, I guess from fuel from the compression test, but other than that everything seems undamaged, including the top of the piston.

I took the valve cover off and all seems ok in there, no broken springs and everything moves as it should.

I don't have anything to do a leak down test, but I guess thats the next option?

What are the possibilities from here? New head? Or is the 150psi suggesting a worn engine. It has been using a lot of oil for a while, but it didn't seem to be burning it, my guess was the rear seal, as there is no smoke and it ran well until this issue.

 

You just need oil for the leak down test. I heard of a few members on here who had this issue with that motor even well before that mileage. It was never the valves but the rings unfortunately.

do these cylinders have sleeves like the 4.0? If not you could at least have the consolation of boring it out for some extra ponies

 

I think 150psi on a warm motor is a little low (should be around 175) but if all are within ~15% of each other it should run fine. Except you have no compression at all in #3

 

Don’t just replace the head. Assume you checked your oil and didn’t find coffee?
At that mileage I’d just get a low mileage replacement motor from a wrecker tbh. They are cheap and plenty.

 

Zero is pretty bad. Like suggested, small bit of oil in the cylinder before cranking...if the compression goes up it is rings. If it stays the same you have other issues.

My thought is with zero compression you have a burnt valve. It would take a lot of damage of rings/piston/cylinder wall/head gasket/head crack to lose all compression. Not to say it isn't possible but unlikely.

If a valve is munched or has incorrect lash just ever so slightly, you will lose all compression.

Not to mention if it all was going into the crankcase or cooling system there would be other symptoms.


If you have it can rent a bore scope, I'd take a peak at the valves.

I also agree that if you have catastrophic damage, just swap a lower mileage motor in. They made tons of them.

 

Thanks for all the replies. I'm going to take a quick look at the valves and do the leak down test. It does sound like an engine swap may be in my future. I'll report back when I have more information

 

Yeah, do a leak down test. I'd think zero compression that suddenly appeared like this would be a blown head gasket, but they usually fail between cylinders.

 

Thanks again for all the replies. Just an update on progress. The leak down test suggested an issue with one or more of the valves. Air seemed to be leaking into both exhaust and intake valves. A boroscope check showed a bit of build up on both but no damage. The next step was to take the head off and probably end up either doing a valve job or more likely replacing the head. Given the mileage, the other oil leak and the low compression I decided to put a re manufactured engine in. I'll put that in another thread because there is some information that others may find interesting