Low compression on cylinder 3 of 2003 Tacoma


#1

I just picked up my truck from my mechanic after he was trying to determine what was causing a misfire in cylinder 3. He swapped coils and then did a compression test and found the following results in cylinders 1 through 4, in order: 143, 132, 57, 151. He said I need to replace the engine or start with adding Engine Restore to see it it helps. Is there a chance I don’t need to replace the engine? Could it need a valve job?
Thanks for any thoughts…


#2

It isn’t a valve job. But I also see no reaosn to doubt his diagnosis. It sounds like he did the right things.

Try some engine restore, or even try some additive that flushes the lubricating system out (in case it’s a gummed up oil ring). But if these things don’t help, your choices will be

  1. boneyard motor
  2. rebuild the motor
  3. buy an already rebuilt motor
  4. live with it and drive the truck into the ground.

Sincere best.


#3

Those sound pretty low across the board, not just the weak cylinder. You can have him repeat the test to verify, and possibly try a squirt of oil in each cylinder, which will tell you if the problem is rings or valves. Either way you’re looking at at least a partial rebuild or engine replacement.


#4

Those readings are all bad and 57 is horrible. He should have followed that compression test up with the wet test version of the compression test. That would determine whether rings or valves are the biggest contributor to the problem.

Odds are it’s the rings on 1, 2, and 4 and maybe a valve on the Number 3 cylinder along with the rings.
Forget any chemical treatment. It sounds like the engine is flat gone either due to miles, lack of regular oil changes, overheating, or any combination of those things.


#5

How many miles on it?? And yes, it could be a valve…And 140psi in an 8.6 to 1 compression engine is not to bad… But you want them all within 10% of each other…


#6

Thanks for the replies. I bought the truck used with 75,000 miles on it and it now has 124,000. I have kept up with oil changes and never had it overheat on me. Sounds like my options may not be great. Should I bring it back and ask him to a wet test? Any ideas on what a 2.7 engine reguild or replacement might cost me?


#7

The truck is almost 9 years old…Look at getting a used engine. Not worth putting a new engine or rebuilt in.

I really can’t talk about price…it’s going to vary greatly depending on where you live (i.e. mechanic hourly rate) and availability of a good used engine.

Not sure why this happened on a otherwise very durable engine design. I’ve seen that same engine with well over 300k miles. But it happens…


#8

Yes, I would do a wet compression test and see if that cylinder recovers. If not, pull the head and fix it…As a first step, check the valve clearances, looking for a tight valve. A valve job would be the least costly solution…


#9

If the compression does recover with wet test, what would be the next step?


#10

The “wet test” is checking to see if it’s the rings causing the low compression. If it “recovers” (shows a significant improvement), that confirms rings and you’re then faced with a rebuild or a replacement motor. That basically means “don;t bother pulling the head, it’s the rings”.


#11

I have to respectfully disagree that a low compression ratio automatically means lower cylinder pressures. If that were the case an 8.5:1 Subaru would not cough up 190 PSI.
Camshaft profile and timing does affect those pressures.

One way to find out; run the wet test and start with the highest one first. (151)
My feeling is that with a squirt of oil it’s going to shoot up to 175, give or take.