Hi all - I recently had a head gasket failure on what appeared to be the 3rd cylinder on a '97 with 3.4L. I replaced the head gaskets, adjusted both intake and exhaust valves to spec, replaced the timing belt, etc. Now I have a no start.

All timing marks are matched up exactly. I get orange spark from single electrode NGKs, and the plugs are wet with fuel. I replaced both the camshaft and crankshaft sensors. The 3x ignition coils are fairly new, after market, and so are the NGK plug wires. The engine went back together appropriately torqued with no parts left over. Before I started the project, compression tests were all over the place and still are off.

Any additional thoughts or ideas on this subject?

If your compression is suddenly varying and wildly inconsistent then it has to do with timing. If compression is varying and there's no start, my first guess would be something like a cam position sensor being unplugged or going bad (if just recently replaced most likely the connector isn't fully seated, but it's still possible to be DOA, I've had knock sensors arrive DOA directly from Toyota). If you're getting spark, fuel, but no ignition AND varying compression, I would almost put money on it being a cam timing issue - but that's just my preliminary guess - I don't know about you but my 4Runner LOVES to have other parts suddenly crap out while trying to fix a related problem in a way very similar to what you described, so from my experience I wouldn't be super quick to start ruling things out

Double check the plug wires are connected in the right order. Sounds basic but I’ve screwed it up before. If they’re good I’d do resistance test on the cam and crank position sensors and the coils. If that’s good I’d double check the valve adjustment. They could be too tight and staying open some I guess. That would be an kit of work to go back into but you could check everything under the intake when you have it off

My signature has a link to a thread with the wiring diagram etc on coils wires and spark plugs.

Sent from my SM-A536V using Tapatalk

Double check the coolant lines going to throttle body as well.

Did you ever figure out the issue?

They haven't logged in since May 2023