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Sorry to disappoint some of you - the coed is my daughter's college roommate.
To add insult to injury - its an S-10 chebbie, 1992, 4.3 V6, TBI??. Seeing all the recent non-Ford postings here, emboldened me to toss this out.
Being a Ford man, I know little about this truck, but told her I would see if any of the great FTE guys could help. The S-10 forums I visited this morning seem populated by goobers and miscreants - no help whatsoever.
I rode with her yesterday as she was trying to describe the problem. When cold, it starts fine but on take off, starts bucking and hesitating something fierce. Some fine gas pedal finnagling keeps it going. Once thoroughtly warmed up, it runs fine. By thoroughly, I mean driving for a long time.
The thing has a carburetor and what must be TBI. Any thoughts?
I've had that problem with my 2.5L S15 more than a few times. Once it was a spark plug wire another time it was the map sensor another it was the egr and another was the computer. It's a chevy shoot it much cheaper. Or offer to give the cute coed a ride in a real truck.. uhhh nevermind just reread the first part.
Usually with the GM tbi's, the MAT (manifold air temp) and/or coolant temp sensors go bad (short) and cause a hard start problem or a lean condition. When the engines cold, those sensors richen up the mixture and it "chokes" the motor. Making it start right up. When they short, it fools the computer into thinking that the engine is warmed up and leans out the mixture and gives you the problem shes having. Hope this helps!
Thanks guys, now I have some rational leads to follow when she brings it over. I would agree its somehow sensor related since it behaves properly once well warmed up. I just hope this thing is not some Pandora's Box of troubles. Appreciate your advice and taking the time to reply.
I would think the Engine Coolant Temperature sensor as well. It should be near the thermostat housing. It is just a resistor that changes its resistance with temperature so can easily be tested with a multimeter and a can of water at various temperatures. When cold the resistance should be high and decrease as the temperature increases.
Chevy TBI's are about the most simple fuel induction devices known to man. And sometimes some of the hardest to diagnose.
There are only 3 sensors: MAP (manifold absolute pressure), coolant temp, and throttle position. The knock sensor is for ignition timing. No air temp sensor. Speed-density systems don't require one.
On older units, the idle control solenoid (IAC) can start sticking. Sometimes it can require removal to completely clean out the ports it controls.
GM MAP sensors are notoriously reliable. Failure is rare, but it does occasionally happen. What CAN happen, though, is that the LINES between the manifold and the MAP sensor can become brittle and crack, thus confusing the sensor. The lines are plastic, with rubber "boots" on each end, giving a "flexible" connection. Other vacuum lines are also prone to this problem, although there aren't many on a GM TBI system.
How come two posts of the same subject within a day of each other? Didn't like the answers in the first post????jd
Nah, some computer glitch with the system here at work. Tried to edit out the second one and leave an ignore message and it didn't take either. Must have been a sunspot eruption.....yeah, that's it.