So I started poking around my car (87 GL turbo), looking for anything obvious, found one of the injector bolts was broken off on the driver's side. Got the broken bolt out and replaced the injector seals on that side, still ran like rump roast. So I poked around some more, and found that the intake boot had come off the turbo, so I stuffed it back on and tightened the clamp, and in doing so discovered that it had a huge crack in it, right above the clamp. So I dug through my parts shed and found a good boot, was off a flapper door style MAF equipped car, but since it's shorter it works better with my cone air filter anyway. Made sure it wasn't cracked and put it on, got it all tight and all the lines hooked up, and it still runs like rump roast and has a funky idle.
Compression is good, timing is good (both valve and ignition) alternator output is good and steady (The voltage gauge does jump around when the blinkers are on, etc.. but the voltage at the alternator stays steady, and this car has always done that as long as I've had it)
Cylinder #4 misses at idle (Was both 2 and 4 before I replaced the injector seals)
It does run better than before, and it goes like a scalded dog when it's cold but once it warms up it falls on its face unless I keep my foot out of it. Under higher boost (7+ lbs) it will start to cut out (Feels like the ignition shuts down for like, 1/2 second or so, about the only way I can describe it, occasionally it will backfire out the intake but seems to not do it anymore since I replaced the tube) but if I keep it under 2-3 psi it seems to be fine, and it has plenty of go off-boost. I've got a few theories:
1) it's got a bad knock sensor (I haven't tried putting a resistor in place of the coolant temp sensor to see if the problem is related to the actual temperature of the engine, or if it's related to what the computer thinks the temp is) and it starts dumping garbage data when it warms up, causing the computer to pull timing
2) It's leaning out, causing it to detonate, causing the computer to pull timing
3) It's got carbon deposits or a hotspot in the cooling system, and the excess heat is causing detonation, causing it to pull timing (Doesn't run hot or make noise or anything gauge wise)
4) Bad MAF sensor?
I'm not quite sure how to test the knock sensor without a scope, and I'm not about to just bypass it and have it be #2 or #3 and I melt a hole in a piston, but the knock sensor looks like a whole barrel of monkeys to replace... Might have to just pull the manifold next time I'm in Albany and replace all the vacuum lines and such (I did this when I put the new engine in my SVX, found like 3 cracked vacuum lines under the manifold... Tempted to just put the old engine back in [Nothing wrong with it, the guy I bought it from had a shop replace the flex plate, and they replaced it with a 4 cylinder flex plate, which shredded on the freeway, picked up a 60k motor for $100 and thought I'd just throw it in, turns out it has a dead hole... So now I gotta pull that one back out, replace the timing belt, water pump, and seals on the old motor, and drop it back in... And I can't do that until I finish the body work on dad's Mustang so we can sell it.. Ugh, too many projects, not enough time!