New 1st Gen Tacoma Owner - Misfire and Low Compression Confusion

New guy here with a 2004 Tacoma 4X4 with the 3.4L. Bought it three months back in Arizona (super clean truck, very well taken care of) with 136k on it. Only thing I noticed was an intermittent rough idle. Drove it cross country last week to NJ to visit family and the truck performed like a champ.

However after a couple days here the CEL came on, I ran a test at autozone and it gave me P0302, cylinder 2 misfire. Local mechanic swapped plugs, checked coil packs and still got the code (so they say). They ran a compression test and said that cylinder is coming in at 80psi.

They said it's only misfiring at idle, but off idle runs fine, which explains that rough idle I've been feeling. I'm wondering why it took all this time for the CEL to finally come on though.

Anyway the mechanic said my options are a fuel injector service or a top engine cleaning to clean off any carbon buildup. I opted to just take the truck home as it's still running fine, except for that occasional rough idle. Could this be a valve problem? I thought maybe they overlooked a plug wire or something but that wouldn't necessarily explain the low compression. My first Tacoma and I'm a little bit bummed bc I got it specifically for the reliability of this engine.

 

If i truly has 80 PSI then it can be a valve problem (not good) or a ring problem (really not good). I have not reason to doubt the mechanic but at 80 PSI i doubt it would ever fire that cylinder. Do you have any idea if he did a dry or wet compression test? You can somewhat tell from those two test if it is a top end or bottom end problem......

 

Welcome to TW Blake

 

might be obvious but I didn't see you list it, when they did the plugs did they do wires too? Had the same issue and plugs didn't go it but wires did.

 

They didn't do the wires but jumped right to compression check. Could bad wires also cause low compression? I can always swap the wires myself since its cheap

 

If not wires I would check injectors. Had this issue and went down the list. Plugs/Wires/Coils/Injectors. Sure enough it was injectors. I would try replacing them before jumping into bad compression problems. Doesn't hurt to cover all bases.

 

Thanks for the replies. Mechanic did a leakdown test and determined it was an exhaust valve problem. Pulled the head and found the culprit:

 

Oooh that is one unhappy valve. What are they recommending for repair?