1991 4.3 Tbi Sonoma/s10 Running Rich Nightmare

Hi, my 1991 Sonoma 4.3 TBI started giving me code 45 (rich), idles rough, stalls, black smoke.
Everything listed here has been done by me or my mechanic, who says he is stumped at this point.
I need some suggestions that are not on my list. Any crazy idea would be considered at this point, THANKS>>>>:confused::confused::confused::confused::confused: :confused::confused::confused:

New egr valve
New idle air control solenoid
New Iac motor
New map sensor
New tps
New o2 sensor
New knock sensor
New coolant temp sensor
New distributor
New coil
New wires
New plugs gapped to .035
New tbi rebuild rings/gaskets
New fuel pressure reg
New fuel pump
New fuel pump sending unit
New spark control mod
Replaced computer ecm
New exhaust/cat



Timing done
Fuel pressure tested at 13 psi
Fuel return line blown out/ no kink
Injector pattern fine
compression test fine 100-110 all

What happens when you unplug one of the injectors? What happens when you unplug the other injector?

The EGR is vacuum operated right? Have you pulled off the vacuum line while it is running.

Hi,
Pulling driver side injector connector stalls it out in about 3-5 seconds, the same for pass side. Pulling egr vaccuum, runs worse, will stall eventually.
Thanks for your interest.

Try running some high octane fuel. This stuff runs hotter and cleaner. Also helps to clean your head valves as-well.
Good luck

Hi,
Pulling driver side injector connector stalls it out in about 3-5 seconds, the same for pass side. Pulling EGR vacuum, runs worse, will stall eventually.
Thanks for your interest.

There shouldn't be any vacuum at the EGR Valve with the engine at idle. Removing the hose shouldn't even cause a vacuum leak at idle? So the fact that it ran worse and stalled has me stumped? It should not run worse with the vacuum hose disconnected!!!!!!!!

What happens if you create a small vacuum leak (pull the hose of of the PCV valve and then partially block it with a finger) does the idle smooth out or gets worse?

What happens If you spray a little carb spray into the throttle body while its idling.

Have you put a vacuum gage on it to see what kind of vacuum you have?

Does the brake pedal feel harder to press than usual?

Are you sure that the cat isn't plugged?

In light of you being stumped, I rechecked the egr, and I believe I was mistaken in saying that it made it worse. I pulled the egr hose off again, but I believe it is just the engine hunting and loping. It's having a hard time idling right. I felt the egr hose at idle, and there is just a slight tappping of suction that increases with rpm, I guess that's right. Pulling the pcv with finger partly over it does not seem to change anything. Spraying carb cleaner into tb stall out engine fast. Brake pedal feel fine. Cat is brand new. I'm thinking of sending injectors out to be tested by witchunter?? It seems unlikely both are rich, I don't know what else to check. Thanks.

That all sounds right.

If it is running rich than you should be able to control a vacuum leak and find a sweet spot where it runs much better (partially blocking the PCV with the finger). If you can't find the sweet spot than I wonder if the rich condition is a mechanical failure rather than an electrical issue.