Idle drops and hesitation

[boostedtsiawd]

When my car is fully warmed up and i put it in drive with my foot on the brake i notice the idle drops down to like 580rpms and there is hesitation what can cause this? I already had the alternator and battery tested and they both passed. It only happens when i press the brake pedal the idle and hesitation happens. There is no cel on either but I noticed one of the brake light bulbs works off and on like there is a loose connection can this be the issue?

1994 Infiniti J30

 

[mclasser]

Perhaps a bad ground somewhere.

 

[Rolla07]

Try cleaning throttle body. Thatd be first thing to try.after that check idle air control valve, it allows you to adjust the idle speed. Might just need adjusting.

 

[LoneRanger]

Check the brake booster for vacuum leak. Check all vacuum hoses through the engine bay for secure fit to their various fittings. I just solved a similar issue on my Forester. It was a vacuum hose that went from the intake manifold just aft of the throttle body assembly and connected to a fitting on the fuel rail. It was not damaged, just fitting a little loose at the intake end due to the rubber had hardened up over time and heat cycles.

 

[Ohle_Manezzini]

My former 95 Golf had up and down idlle and the idle screw at throttle butterfly axle was too much retrieved.

 

[Astro14]

Only when you press the brake pedal sounds like a vacuum leak in the booster as was said above.

 

[Bgallagher]

Originally Posted By: Astro14
Only when you press the brake pedal sounds like a vacuum leak in the booster as was said above.


+1

 

[boostedtsiawd]

Also when im in drive foot on the brake pedal with lights on u hear a noise but when i turn the lights off it goes away im thinking alternator maybe?

 

[mjoekingz28]

Doesnt the brakes use boost that comes from the engine vacuum?

If so, then maybe that is it and not electrical.