Accelerating by itself, even in park

SHARDA KALLADEEN

MEMBER
2001 CHEVROLET SILVERADO
6.0L
V8
4WD
AUTOMATIC
160,000 MILES

I changed the EGR and the truck drove fine that day. The next day, it started accelerating on its own while on the highway. Pulled off the highway way and put the truck in park and it was still accelerating on its own. I had the scanner which had codes for the idle air control, the throttle position sensor and the MAP sensor. I replaced all them and it still does the same thing. As soon as I turn on the truck, it starts accelerating, almost like a runaway engine. It is not a diesel truck so I am really stumped.

Thursday, May 17th, 2018 AT 3:33 PM

1 Reply

STEVE W.

MECHANIC
15,244 POSTS

I would start by looking for a vacuum leak. Remove the EGR and verify the gasket is correct, if they are cracked or flipped on some they will cause a leak. Check all the vacuum hoses as well. It does not take a very large leak to cause the engine to run faster. Being seventeen years old the lines are probably getting pretty rough and with the higher RPM a leak will be hard to hear so check them first with the engine off. Do not forget to check the brake booster line and the PCV line.
I have knocked more than a few off and suddenly discovered the engine wanting to "idle" at 2,000 rpm's!

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Friday, May 18th, 2018 AT 10:38 PM