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car running rich


10+ Year Contributor
Jan 17, 2010
kenosha, Wisconsin
this may sound really weird but when at idle on the wideband runs around 14.7-16.8 or so and when i push on the break pedal my car will run rich like in the 10's when i take my foot off it goes back up i have a 97 gs-t

One more question is the car suppose to run at 14.7 at idle and while cruising i hear different opinions


15+ Year Contributor
Mar 4, 2008
East, Maine
when you push on the brakes that cause some kind of vacum in the motor but my car does the same thing its weird.

when your motor is at idle there is vacuum in the intake manifold. vacuum is kinda like the reverse of pressure. and when you step on the brake your brake booster "fills" with vaccum so there is less in your intake manifold for a few seconds which makes your fuel pressure rise.


10+ Year Contributor
Dec 3, 2008
Shelbyville, Kentucky
mine does the same but my voltage also drops to about 12.8-13.5 sometimes when im at a stoplight with the brakes pressed. The car also idles down and wants to run rough but as soon as im off the brakes its fine..
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