Alright, the car was running fine for the 2 hour drive from phoenix, and i got home and let it cool down. I go and replace the engine mounts, and then take it for a test drive, and BAM it starts detonating as soon as the turbo begins to spool (about 3500 or so, under light load) without fail, every time. It also sounds that it detonates once right when i turn the engine on, a quick "creak" as soon as the engine catches.

Im puzzled, i dont know why out of the blue this would start, also now my car is idling very rough, backfiring more frequently than usual, and making a slightly different smell. I checked vac lines... i dont know what else it could be? Timing? but i dont see how the timing could magically change on me like that, it was fine for the last year.

What can i check? Im stumped and a little nervous... im scared to put it on a compression tester.... maybe the problem will just go away if i ignore it

 

Also, the car still runs as long as i dont let the turbo boost at all. Keeping it below 3000-3500 is ok. No detonation, and it seems to run fine as long as i dont boost.

 

Pull your EGI fuse and listen as you crank. Listen for 3 even "wooshes" if you do here them, your seals should be ok and start working on the detonation problem. If you hear 2 good strong wooshes and a weak one, well you probably have a blown apex seal.

Another way is to pull a spark plug and stick your hand there as someone else cranks and this way you can feel the wooshes.

 

You forgot pull a spark plug, it'd be kinda hard to hear the whoosh with all the plugs in there

I figure while im seeing if i still have all my seals, i should also see what kind of compression im getting.

I've yet to check my timing, but im almost sure thats not the problem. What could the detonation at such an early rpm and low load level be caused by?

 

apex seals lose compression on 2 faces, side seals lose it on one.
and "creak" doesnt sound like a typical detonation sound. most people say something like "metallic popcorn." and i have never heard of detonation on start-up. that sounds highly unlikely.

 

I have no other explanation for the sound, actually it sounds very similar to the sound a match makes when you first strike it... it doesnt sound very metallic to me. And the sound it makes when under boost (what i think is the detonation) it makes that same sound on start-up sometimes.

I dunno, its like a creak/match-strike... doesnt sound very metalic.

 

Check the spark wires - you may have leading & trailing reversed.

A low speed, low power knock probably did no harm.