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Gmc truck dies when i stop

i have a 1998 gmc sierra 2500 truck when i start it it runs just fine but after i have driven it awhile when i go to stop as soon as i come to a stop the engine revs up and down and it dies it will not do it if i am in neutral or the engine is cold any ideas what could be causing that . ty

Check engine light?

The idle air control valve (IAC) controls the air for the idle and if it is squirrely it can cause the revving up and down and stall the engine. It costs only a little time and money to clean it so there’s not much reason not to.

But it shouldn’t make a difference to the IAC whether you’re in neutral or not. (Cold/hot can make a difference with the IAC). I assume this an auto transmission? In that case, I’m actually going to suspect that you have a torque converter clutch (TCC) that not unlocking. It would end up being like stopping a manual in gear without depressing the clutch. If you have an “overdrive off” (or O/D off) option try it out & see if it changes anything. That normally disables the TCC lockup.

How many miles are on it? Give all the details you can about maintenance history.

Gasket air leak between Carburetor and manifold

A 98’ GMC Sierra has fuel injection.

If you have an “overdrive off” (or O/D off) option try it out & see if it changes anything. That normally disables the TCC lockup.

x2

missileman

You are correct. I should have printed " 89 "

A 1989 Chevy pickup was still injected, no carb. 1987 was the first year for injected Chevy trucks . I would have to go with Pumpkinkrasher on the TCC. Unfortunately there is no switch for OD or TCC.

It can still be a gasket leak. I have the same truck. Mine is not fuel injected. It has throttle body injection. Some kind of precursor to fuel injection. My truck still has a manifold and the throttle body of a carb. Just doesn’t have all the inards (I don’t think it does?)