OT need help 1998 Chevy silvroda P/U

Farmer(Ga) · Jul 11, 2012

When i let off gas the truck will go maybe 200+- feet before engine will start backing down. I took it to a shop with a good rep and they cleaned the TB but that didnt work. They put the comp. on it and it said all was working like it should but wasent returning ever what that meant. They called a macanic at the dealership and he had never heard of it either and if it was not the TB sticking he didnt know what was wrong either. Anyone have any idear what the problem could be? Since a light stroke and cant get my right leg from gas to brake without lefting with my hand i have parked it. I am old but would like to live to be a little older. Thanking you in advance for any info/advice. James

Lou from Wi. · Jul 11, 2012

Just a guess,but did they check the throttle posion sensor? It might be the culprit.
LOU

Farmer(Ga) · Jul 11, 2012

Thanks Lou, I dont know if they did or not but will check and see if they did. James

karl f · Jul 11, 2012

if it isn't idling fast enough, it might be the idle air control motor.

karl f

504 · Jul 11, 2012

Intake gaskets are going bad causing a lean condition, so the computer richens the mix causing the delay. Mine would take a mile to coast from 70 MPH down to 55 MPH. Make sure they use Fel Pro Problem Solver gaskets.

Sprint 6 · Jul 12, 2012

It is most likely the throttle position sensor, as has been suggested. I have seen it cause a runaway idle on a lot of GM vehicles. It will look OK on scan tool data because the glitch happens so fast not even a GM Tech 2 scan tool can catch it.

Mike in Mn. · Jul 12, 2012

I have an old 95 buick that is doing the same thing!!! Changes the tps and the idle air controller and it didn't change a thing, it will run about 65 with your foot off the pedal and it's not the throttle sticking. If you shut it off and start it right back up it's ok.

RWT · Jul 12, 2012

Sprint 6, I will second that.

I worked on a 2000 Monte Carlo that set a code for the TPS and I couldn't see a thing wrong with it.

When it wouldn't slow down again until he hit the brakes I replaced it and he hasn't complained since.

RT (my 2 cents)

luv2wrench · Jul 12, 2012

Take battery cables off, both of them, and touch them together. that will reset adapts in the PCM.

Clean the MAF (Mass Air Flow sensor) right after the air filter with a carb cleaner and blow it off as soon as you get it cleaned.

If the intake gaskets would be leaking here is how you tell.

UNHOOK and Plug the PCV tube and port on driver side valve cover. Then pull off the breather tube on the passenger side valve cover that goes to the throttle body inlet tube. If the intake gaskets are out (inside the engine, NOT OUTSIDE!) your hand will get sucked into that tube on the passenger bank.

When i see an intake gasket leak on a 5.7 L31 itss almost always internal causing the problem. Sucking air from inside the intake valley, not the outside.

how this helps.

(I see this issue all the time on MANUAL TRANSMISSION truck that when they step the clutch RPM"s race higher before going down when coming to a stop sign. That is a software glich and those trucks and can"t be corrected. My 96 4.3 V6 GM C1500 does that all the time.

From your post i assume you have an automatic 4L60E transmission.

TonyIN · Jul 13, 2012

Had a '90 that did the same thing. Same issue - bad intake gasket.

OT need help 1998 Chevy silvroda P/U

Farmer(Ga)

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Lou from Wi.

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Farmer(Ga)

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karl f

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504

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Sprint 6

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Mike in Mn.

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RWT

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luv2wrench

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TonyIN

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