Mechanics

CHEVY ENGINE STALLS WHEN WARM UPON STARTUP

1993 Chevrolet Silverado

Engine Mechanical problem
1993 Chevy Silverado V8 Four Wheel Drive Automatic 143000 miles

The truck starts and runs fine until it is parked for a short while (maybe 15 min) then when I go to start it again (while still warm), it has a hard time running. It wants to stall unless the gas is pumped to keep it going (but then just barely). This only lasts for about a minute then it runs smooth again as if something just got cleared out of the gas line or the choke just got unstuck? I recently changed the fuel and air filter with no improvement. Any suggestions would be appreciated.
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Tshad
February 21, 2010.



Has the check engine light come on?

No, the check engine light has not come on. I found a similar question someone else asked that a technician answered. He said it could be the throttle position sensor, the idle air control valve, vacuum leaks, or the EGR. I will look at these things unless you think it might be something else.

Tiny
Tshad
Feb 22, 2010.
I would start with the EGR / vacuum. As far as the other things, they would cause a rough idle but I've never seen them prevent an engine from actually starting.

Correction: the engine does start 99% of the time, but almost immediately it starts to idle rough and if I don't pulse on the gas it almost always dies. Again, it does this for about a minute, then its totally fine until the next time I stop for a while then try to start it again while still warm.

Tiny
Tshad
Feb 22, 2010.
It could be any of the items mentioned. Start with the cheapest fixes first, vacuum leaks and check the EGR for carbon build up. Also, let me know when the last tune up.

Joe

This afternoon I took off the EGR. It only had a bit of carbon build up - just a thin coating. The diaphram moved up and down freely by pressing it and air came out the little hole at the outlet spigot. I don't have a vacuum pump so I couldn't do an official test.

The throttle position sensor (TPS) test: With a voltmeter I checked terminals A and B. It was 5.03 volts with the key ON, engine off. However, terminals C& B only read 0.01 Volts. The Chilton manual states it should be 0.5-1.2 Volts. Also nothing happened to the voltage when I moved the throttle open and closed. Does this indicate a faulty sensor?

Idle Air Control Valve (IAC) test: Using an ohmmeter, terminals A& B and C& D both read on average 49 ohms which falls within the manuals parameters of 20-80ohms. However, when I went to remove the IAC, it unscrewed so easily that it was only about finger tight- maybe even less. The recommended torque is 13 ft lbs. For lack of a 1 1/4 socket to fit my torque wrench I don't know if this was correct but seemed not quite right to me. Everything looked ok with it so I put it back on. A little tighter this time. Could this looseness be a part of my problem?

Lastly, I found that a mouse had chewed the end of the vacuum hose going from the EGR solenoid to the EGR. The boot end separated from the hose so I reinserted it a little deeper and taped it with electrical tape. I live out in the boonies so I don't have immediate access to parts. Will replace it later.

I purchased the vehicle only last year and I have not had it tuned up. Not sure when the previous owner had it tuned up last either.

Hope these small things I did will help.. Any feedback would be appreciated.
Thanks
Gerry

Tiny
Tshad
Feb 22, 2010.
Based on your info, it sounds like you need a new TPS. As the leaks you found, they could play a role in the problems too.

Let me know how it goes for you.

Joe