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454TBI will not idle under load
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Posted by: struck

I have a 1993 C3500 Chevy truck with the 454 TBI engine with an automatic transmision that will not idle under any load and mostly will not idle at all and I am not getting any engine light or codes from the computor.
It will idle when cold but when it gets worm it wants to stall. When it does idle it wants to stall with vary little load. (turning the wheel, turning on the AC, hitting the breaks.) and will not idle in gear at any time. It acts like a bad IAC modual but the problem did not stop when it was replaced.
I have also replaced the fuel injectors, fuel presure regulator, fuel filter, MAP sensor, throttle position sensor, spark pluges, wires. cap and rotor. I have also cleaned the throttle body, blocked off the EGR valve, check every thing I could think of for vacum leeks and still it will not idle.
I have talked to a dealer mechanic and he told me that without any codes he would have to start changing parts to see what worked!!
If anyone can help me it would be greatly appreciated.

Please help Struck

Posted by: skeezix

Check for a vacum leak somewhere. Spray wd40 around the intake manifold, tbi mount, vacum ports, etc. or anywhere there's a source of vacum. A change in engine rpm will indicate a vacum leak.

Good luck.

Posted by: cswrench

Some of the older TBI Big blocks had idle kickers on them (a solnoid that bumped the throttle arm up) If it does make sure it is operating normally. Also some get removed and not put back on. They also get out of adjustment. key off the kicker shold be just BARLEY touching the throttle arm.

Posted by: struck

I will test for vacum leaks again the first I used Chemtool with no indacation of leaks. My truck does not have the solinoid throttle kicker, All the info I have received so far says it is electronicly controled.

Posted by: struck

I looked for vacum leeks again and found no leeks and still no luck getting it to idle.
Any body else have any ideas.

Posted by: skeezix

Install a throttle kicker.

Posted by: struck

This truck never had a throttle kicker

Posted by: struck

My idle problem finnaly turned out to be the distributer. I could not test the old distributer to see exactly what went bad (the modual or the pick up) But when I put in a rebuilt it idled. I am just happy to get fixed.

Thanks for your suggestions
strusk

Posted by: cswrench

Cool! Good job!

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