1990 Chevrolet Truck

90 lumina
4cyl. 2.5L 126,000 miles

my car has been running rough and stalling out. To be more specific, car runs rough from the start and when the car has warmed up it will begin to act like it wants to stall. If I'm going down the highway and slow to make a turn or come to a stoplight, it will stall as I'm slowing down. Sometimes it will die as I'm accelerating as if the fuel just cut out. When it stalls it takes 10-30 minutes before I can get it started again.
Once when it stalled I discovered that there was barely any fuel coming out of the injector.
I have replaced the injector, fuel filter, and sparkplugs. Whenever I scan the computer, I get no codes, even when it has just stalled.
I'm not sure what to check next so I would greatly appreciate being pointed in the right direction.

Today the car finally gave me a code 34 so I replaced the MAP sensor. Car still running rough but left it run for a short while and it didn't stall so far. A storm moved in so I had to shut off the car and go inside. Will let it run longer tomorrow.
while changing the MAP sensor I noticed a crack in the TB housing. Could this be causing the roughness? I'm guessing that this may be causing a vaccum leak.

I have since inspected and cleaned the IAC valve and tested the EGR valve. Engine stumbles when egr plunger depressed, so that is okay. Still present is the loping/surging idle. Also replaced TB Housing (well I guess it's acurately called the air box or air cleaner top).

more to add: I got a code 35 (iac valve), replaced it, hooked everything back up. Started the car and it was running great but the engine light kept coming on with the same code for the IAC. I reset the computer and it was still giving the same code. I got under the hood to recheck the valve and realized that I forgot to plug in the electrical connector. I plugged it in and now the car is running just as bad as before if not worse. It idles fine in park, but if I'm just sitting there in gear the idle is low and rough and when it starts to stall the engine revs itself. After letting the car idle in drive for about 20 minutes it finally stalled again and the computer gave me no more codes.

summary of replaced parts:
fuel injector
fuel filter
spark plugs
MAP sensor
IAC valve
tested EGR valve
unplugged TCC solenoid
June 19, 2006.

Try pulling the plug on TCC solenoid. That should solve your highway to stop problem.

Jun 24, 2006.

Jun 25, 2006.
Bump for help

Jun 26, 2006.
Found the problem. The infamous vacuum leak. Plugged it and the car is purring like a kitten.

Jun 30, 2006.
My lumina euro idles a little rough sometimes but im not too worried about that, the main problem is that when it gets hot ( running temp.) It sometimes sputters then stalls, if I give it gas it will restart and I have to keep giving it gas or it stalls if I try driving after the initial stall it barely wants to get out of its own way. Ive seen alot of talk about clogged catalytic converters and also the torque converter lockup solenoid but I have no idea what to do. The computer comes up with 5 codes (1)-23 manifold air temp to low, (2)-21 throttle position sensor/ckt high, (3)-15 coolant temp signal high or open (4)-53 system voltage to high (5)-43 esc module or sensor circuit problems, also the scanner says that my systems voltage is 25.5 volts and the fuel pump is getting 25.5 volts when its acting up. PLEASE HELP

Mar 21, 2007.