1997 Chevy Tahoe Misfire

POOH123

MEMBER
1997 CHEVROLET TAHOE
V8
2WD
AUTOMATIC
166,000 MILES

I was going to turn the vehicle around and it misfired dramatically. "I think it broke either the "cat" or the baffle. Had just started the vehicle and was going to put it in drive when this happened. Now it starts and screams untill the rev limiter shuts it down.
Could this be the crank sensor?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Has the check engine light come on? Also, have you checked the throttle cable to the throttle body to make sure it isn't stuck wide open?

Let me know.

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Friday, November 13th, 2009 AT 10:31 PM

POOH123

MEMBER
6 POSTS

There was no service engine light prior to this. I didn't notice it on afterwards but when you start it it only runs for about 5 seconds befor it shuts down and no the throttle is not stuck

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Saturday, November 14th, 2009 AT 5:40 AM

POOH123

MEMBER
6 POSTS

I ran the truck plenty long enough to get A service engine light and it never came on. Then I disconnected the TPS and started the truck and almost instantly the light came on. Then I foud that the backfire was so severe it actually blew the gasket out under the plastic intake which is probably the reason for the revving. The big question is what caused the backfire in the first place.
I'm off to the auto parts store to buy A replacement gasket.

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Saturday, November 14th, 2009 AT 9:24 AM

POOH123

MEMBER
6 POSTS

I replaced the gasket and everythin except for the muffler (broken baffle) is fine.
Still don't know what caused the backfire though. No service engine light. And truck is running great.

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Saturday, November 14th, 2009 AT 1:10 PM

PEAR69

MECHANIC
1,482 POSTS

The TPS will not cause the throttle to stick wide open (which is what happened). The throttle is controlled by a cable that attatches from the foot pedal to the throttle body -- it is a mechanical setup. The TPS is a rheostat sensor that tells the computer how far the throttle body is open.
It sounds to me that there is either a problem with the throttle body or the throttle cable.
With the engine off - disconnect the throttle cable from the throttle body. Operate the butterfly valve on the throttle body by hand. Check for smooth operation while opening and closing. If it sticks at any position it must be replaced. DO NOT grease - oil - or clean the throttle butterfly.
Check the cable in the same manner, make sure it is operating smoothly -- and make sure that a floor mat is clear of the throttle pedal.

The back fire probably came from the over-reving of the engine. The only way for that to happen is the throttle was stuck or pressed wide open.