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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: 462
Loc: Atlantic, Canada
Any of you experience a bad gas cap? If this can affect engine performance, fuel trim or fuel pressure? fuel economy?

2011 Chevy Cruze 1.8L 6AT
AC Delco Dexos 5w30 - OEM filter

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

Registered: 12/19/04
Posts: 7355
Loc: beaver land EH?
on OBD-II cars: a bad (not sealing properly) gas cap will throw you a code.

"Internet discussion boards act as echo chambers for conspiracy dittoheads" A.Allen

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

Registered: 05/18/08
Posts: 618
Loc: DuQuoin, Illinois
It will give a code for evaporation system leak usually.

#2767417 - 10/09/12 09:53 AM Re: Symptoms of a bad gas cap? [Re: wolf_06]
440Magnum Offline

Registered: 02/01/09
Posts: 8404
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.
'66 Dodge Polara & '69 Dodge Coronet R/T both 440/727
'08 Ram 1500 4.7/545RFE
'12 Challenger SRT8 392/6-speed
'99 XJ 4x4 4.0/AX15, '14 WK2 4x4 3.6/8HP

#2767479 - 10/09/12 11:19 AM Re: Symptoms of a bad gas cap? [Re: wolf_06]
WishIhadatruck Offline

Registered: 05/09/06
Posts: 1326
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.
1996 Buick Roadmaster Wagon
2014 Cruze Eco Manual
2003 2500 Suburban, 8.1L

#2767495 - 10/09/12 11:39 AM Re: Symptoms of a bad gas cap? [Re: wolf_06]
Donald Offline

Registered: 03/21/04
Posts: 17418
Loc: Upstate NY
I drove for a few miles with the gas cap held neatly in the gas flap. No code or anything.
2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)

#2767501 - 10/09/12 11:43 AM Re: Symptoms of a bad gas cap? [Re: Donald]
Trav Offline

Registered: 11/20/06
Posts: 14420
Loc: MA,
It wont until the system runs an EVAP test.
ASE L1, Master. Deutsch Meisterbrief.