Idle drops while braking---nicoclub search isn't working

[WhiteKnight]

Sometimes when I brake my idle will drop and then rise back to normal.

If I'm at a red light....and I just touch the gas pedal lightly....rpm goes up and then drops to100 or 200rpm and then climbs back to normal.

What would cause this besides the brake booster check valve?

[nismoracingsx]

Guessing you already replaced your valve...checked the brake booster hoses themselves too right?
If your car is choking a little when you let off the gas, i would check the throttle body to see if the idle air control valve is clogged making it hard for your car to breath at idle. My car used to dip like that and my tb was all gunked to hell.
GL

[WhiteKnight]

I called a junkyard who wanted $40 for the check valve......so I'm waiting til monday to call Nissan. Brake boost hoses are new...but brake fluid was low. The idle doesn't drop every time I come to a red light. I found the plug wire #3 was loose also. The IACV is 4 months old.

[shiro_neko]

sounds like your idle adjust screw is not opened enough. check your IACV if its connected properly. remove your TPS harness. I suspect your idle would around 500rpm or lower. adjust it if it does.

[ride_240]

had the same issue. its your throttle plate. actually just finished cleaning mine. literally about 2 hours ago. buy some crc throttle body/intake cleaner ($5). take yur intake out and you should see the throttle plate. spray it with the cleaner and scrub away with a old toothbrush and wipe with a old rag. Will have trouble starting at first but it will with a little gas on d pedal. and den d idle will fluctuate...just drive it for a bit and itl be fine. did wonders for me (no more dipping rpm)!
initially i thought it was misfiring...i changed the distrubutor rotor, ignition wires and sparkplugs..was ok for a bit but then at idle it would dip sometimes stalling.

[Klits562]

It could also be a vacuum leak. I had this same problem when braking i heard somewhere that if your idles dropping from vacuum leak its somewere before the throttle body so i checked all my intake piping and turns out my maf was a little lose from the intake piping so i shoved it in and tightened the clamp and my problem went away.

[zer0c123]

It could very well be an electrical issue. I had the exact same problems for years and always suspected the IACV valve or fuel injectors. I ignored the problem for awhile, because the rpm's never dropped to where the car would stall. However, the car starting to stall last winter so something needed to be done. I cleaned out the IACV valve and replaced with new injectors from Deatschwerks. Car ran a little better, but the rpm problem remained.

I discovered that my TPS sensor was the problem. I had repaired the tps sensor years ago because the ground wire broke off. It turns out my solder and e-tape job wasn't holding up. After inspection, the area where I soldered and e-taped was full of green cancer (corrosion build up). I spliced a new connection and now the car runs perfect with no dropping idle on braking.

So check for electrical problems. Jiggle all the wires under the hood and see if the idle changes. Start with the wires that run above your injectors and work your way from there.

[MadScientistCreations]

Hey, if both symptoms appeared at the same time I might have something to check for you. The check valve on the booster just retains vacuum in the booster. Which means that if it goes bad it usually affects the ability of braking under conditions when the engine vacuum is less. That being said, its probably not the check valve. There is a possibility that the diaphram in the brake booster has developed a tear. This would be a source of air into the system that is not being metered by the MAF. Thus affecting idle. This would be more apparent during braking because vacuum is increased and pulls on the tear. It could also explain the throttle issue but could be two separate issues all together. If you have a hand vacuum pump, hook it up to the brake booster and see if it holds a vacuum. If not, start with replacing the booster first. Hope this helps.

[WhiteKnight]

I did all of the above. It doesn't always dip. But when I cold start the car--the idle bounces up & down until warmed up

[locoluna825]

Sometimes mine dips too on startup like white nights, on cold start up. and at stops and on deceleration. Not all the time but occasionaly. Im gettin ready to disect the whole engine harness and inspect it and replace all the ev1 connections.

It used to do it the most at stops or on deceleration.Then i cleaned my IACV, cleaned my maf, and replaced the O2 sensor and the dipping went away. Now it does the oposite, the idle goes up at stops to like 1300 rpms or sometimes just 1000 rpms for about 3 seconds then drops back down to normal. It only idles high only once in a while though. Its normally around 1000 on decel or at stops, then drops down to normal.