I've been having a strange problem with my DET powered 91 classic lately. Sometimes at idle it will hunt between 500-1000 and runs pig rich (i.e. visible black smoke out the tailpipe). When it is running like this it also hesitates very badly at part open throttle conditions until it gets into boost then it just runs ok (but not as good as normal) and lots of smoke is visible at night when at wot or close to it. It seems to happen more often when under higher electrical loads i.e. headlights, wipers, fan is on. Even when it is running well if I turn on a bunch of accessories the idle will start to hunt. Once in a while it will just start to run bad for no aparent reason at all. It seems like its either an electrical problem or vacuum leak. This is an intermitant problem, sometimes it runs as well as ever and sometimes crappy like I described.

I've tried:

regrounding maf again
squeezed pvc hose
looked for other vacuum leaks after maf
tested alternater with dvm got 13.6
tested battery both on and off got 13.4 on and 12.82 off
tested maf wires
tested tps

I can't seem to figure this out


Thanks for any help

maybe you have a leaky injector o-ring. I had a few before and it would run good sometime snd crappy others. Afyer i changed it , everything was fine. Maybe you might want to verify your ignition timing and check 02 sensor as well.

When it is running like this I've unplugged the 02 sensor and injector wires one at a time and it made it run worse.

You know, I had a prob with my t25 DE setup running rich. Could not figure it out for the life of me... o2, maf, vacuum lines, TPS, fuel pressure regulator, checked for vacuum leaks in the IC plumbing... just couldn't figure it out. I would get the 0706 and 0302 codes from the ecu (fuel injection system, egr). plugged up the EGR so it wasn't that.

My car was pumping out black smoke at idle and WOT. Could tell real easily how much smoke was coming out the back at night with the headlights from the cars behind.

Went on a massive road trip and about 500 or so miles in, the motor was kinda sputtering and hesitating a bit for a while. Then it all cleared up and ran perfect. checked the plugs and they were clean (no more soot), car got decent gas mileage vs. the 13 mpg I had been getting in the city.

I still don't know what the hell was wrong.... but it runs perfect now! Weirdest darn thing ever I tell ya...

Khiem