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#2767398 - 10/09/12 09:26 AM Symptoms of a bad gas cap?
wolf_06 Offline


Registered: 06/11/12
Posts: 408
Loc: Atlantic, Canada
Any of you experience a bad gas cap? If this can affect engine performance, fuel trim or fuel pressure? fuel economy?

Thanks!
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#2767401 - 10/09/12 09:30 AM Re: Symptoms of a bad gas cap? [Re: wolf_06]
Quest Offline


Registered: 12/19/04
Posts: 6075
Loc: beaver land EH?
on OBD-II cars: a bad (not sealing properly) gas cap will throw you a code.

Q.
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#2767404 - 10/09/12 09:32 AM Re: Symptoms of a bad gas cap? [Re: Quest]
Charlie1935 Offline


Registered: 05/18/08
Posts: 283
Loc: DuQuoin, Illinois
It will give a code for evaporation system leak usually.
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#2767417 - 10/09/12 09:53 AM Re: Symptoms of a bad gas cap? [Re: wolf_06]
440Magnum Offline


Registered: 02/01/09
Posts: 5746
Loc: Texas
Electric fuel pumps for EFI generate pressures on the order of 50 psi, the gas cap holds a pressure of 2-3 pounds. So at most its going to make a few percent difference in fuel pressure, and most likely not even that since the fuel pressure is usually regulated. So I'd say you'd never see a difference in performance at all, just the code for an evaporative emissions fault.
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#2767479 - 10/09/12 11:19 AM Re: Symptoms of a bad gas cap? [Re: wolf_06]
WishIhadatruck Offline


Registered: 05/09/06
Posts: 1245
Loc: Grand Rapids, MI
The only thing I've ever noticed is that my check engine light comes on. I've never noticed a change in how the vehicle performs.
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#2767495 - 10/09/12 11:39 AM Re: Symptoms of a bad gas cap? [Re: wolf_06]
Donald Offline


Registered: 03/21/04
Posts: 12608
Loc: Upstate NY
I drove for a few miles with the gas cap held neatly in the gas flap. No code or anything.
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#2767501 - 10/09/12 11:43 AM Re: Symptoms of a bad gas cap? [Re: Donald]
Trav Offline


Registered: 11/20/06
Posts: 8442
Loc: MA, Mittelfranken.de
It wont until the system runs an EVAP test.
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