Strangeness in performance

[sleepy]

Ok guys, I have some really strange engine behavior going on. Even at idle this happens. Symptoms:
Seems to run fine when cold.
When warm, surges (not rhythmically) and runs like crap.
Even at idle, will sometimes run fine and other times knock like crazy (like a diesel truck) and even die.
The noise and performance is so bad that I'm very reluctant to drive it!

I currently have no way to see the OBD1 output. Any suggestions?

Thanks Mucho,

Barry

[prophecymiller]

I'm not sure if closed-loop uses the maf or not, but that's what I would check to make sure there are no leaks between the maf and turbo.

Edit: Just realized if it only happens once it warms up, I would check your O2 sensor since it could be causing a faulty reading once it's cycling.

[sleepy]

I'm not sure if closed-loop uses the maf or not, but that's what I would check to make sure there are no leaks between the maf and turbo.


No leaks there.

[sleepy]

Just realized if it only happens once it warms up, I would check your O2 sensor since it could be causing a faulty reading once it's cycling.

Was leaning toward O2 or Knock sensor - however, wouldn't the O2 sensor cause a CEL?

[sleepy]

Could this be the ECU going bad? Is there an easy way to test for that?

[D Walker]

check for caps leaking

check for boost/vac leaks

check your coolant temp sensor is actually working right

A list of mods/recent repairs would help

[sleepy]

Mods:

2g MAF (on two years)
18g (swapped out e316g thinking that was the cause - and it was really tight).
Balanced Shafts removed
550 injectors
ForcePerfomance exhaust manifold (last month - see rebuilt head)
Rebuilt head (last month) - spun timing belt a month ago in driveway at work. Was not running down the road - basically went to start and it started free wheeling. No damage to pistons or anything was noticed.

Ran well after head for about a month. Then started just dropping off boost like turbo was going out. Quickly degraded from there. Started idling rough and had no boost when driving and also missing.

before turbo was replaced - compression tests 135-150 so I figured that wasn't too bad.

[sleepy]

Ok, I'm just having the car towed to Jack's tomorrow. Just can't seem to get to the bottom of this. Thanks, for everyone's help. Watch for Jack's questions next :D