rogan

iTrader: (7)

Picked up a '91 na, trouble starting, horrible cold idle. Check engine light on, had code 09. While changing out thermister, discovered pins had pulled loose inside connector. Clicked terminals back into connector and reseated, cleared code 09. Car now stars okay, but still has rough cold idle with backfires until warm and then idles perfect. After fully warmed up, if you rev and hold at 2000, 3000 or 4000 rpm it has constant mini popping backfires, but smooths out inbetween. It pulls hard under load running it down the street.
I have adjusted the Tps via the fsm, new stock plugs, new ngk wires. Checked leading timming dead on the yellow mark and verified advance was working. Wasted a huge amount of time chasing ghosts with trailing timming. My timming light is rock solid on the leading timming, but only sporadic trailing pulses. At one point I had enough pulses on T1 to verify I was on the red mark. It worked fine for trailing on my GSL-SE but not on this second gen. After troubleshooting coils and changing out trailing assemblies and still no trailing timming, I pulled the wires off the trailing coils one at a time with the engine running and verifed good solid arching.
I even checked for vac leaks with a propane bottle, but my warm idle stayed rock steady and never changed.
So I still have rough, backfiring cold idle. Perfect, smooth warm idle. And then rapid mini popping backfiring at 2000, 3000 and 4000 rpm, smooths out inbetween. Any ideas?
Thanks in advance..

rogan

iTrader: (7)

Forgot to mention, that during warm up, the AWS seems to function correctly. She revs at 3k for a while, then steps down to 1500 for a bit and then finally to 800 rpm. The cold backfire problem is probably mostly due to the engine being held at 3000 rpm which is a backfire trouble spot.

lduley

iTrader: (1)

When the engine is cold the computer is dumping alot of fuel, just what they are programmed to do

About the only other thing you can do is adjust the variable resistor per the FSM (if i'm remembering the components name correctly) as that will lean/richen the idle mixture depending on which way its turned

Lower compression could be a factor too, along with a stuck injector

Shouldn't be reving it above 3K cold anyways honestly

rogan

iTrader: (7)

I did adjust the TPS per the FSM. S4 have an idle mixture adjustment by the airbox, but S5 do not have one. Also she backfires at 2k, 3k, and 4k when warm, not just cold. But she smooths out inbetween these rpm ranges. What is a good way to check the injectors?