problem when stopping

[knight_240]

got a 93 240sx 5-speed with really low miles. its starting to act funny when i come to a stop, the rpm's seems to bounce up and down between 300-700rpm's and then goes back at idle(around 700rpm)! has anyone experienced this problem? if so..please give me advice. thanks for your help!

[Rev_D21]

You may have a vacuum leak somewhere. The brakes use engine vacuum to assist in braking but if there is a leak the engine could run poorly when using the brakes. Check all hoses for cracking.

[95hardbody]

its starting to act funny when i come to a stop, the rpm's seems to bounce up and down between 300-700rpm's and then goes back at idle(around 700rpm)!

This is a common symptom of having problems with the idle speed control system. I'm actually not sure what Nissan calls it...GM calls it an "Idle Load Compensator", "Idle Speed Controler", "Idle Speed Motor", etc. If the shaft is sticky or binding for some reason (maybe someone used lubricant in the past), it can do that. Or...your TPS (Throttle Position Sensor) is possibly gone out of adjustment. Does your check engine light at any time during this?

[knight_240]

no, there is no check engine light. it just acts like its gonna die when i stop...eventually after 5-10seconds it goes back to normal idle. is it a pain in the *** to fix?

[knight_240]

thanks!! both of you for your help!

[95hardbody]

Does it also happen with the A/C on? Or ONLY with the A/C on? Or ONLY with the A/C off? If you notice it when you're not running the A/C, try turning on the A/C and see if the problem doesn't go away. Let us know.

[knight_240]

i have tried the A/C and defrost on and it still did it. The past week have been really cold and it started doing it, today was warm(about 48degrees) and the car didnt do it all day when it was nice and warm. Tonight(around 30degrees) I took it out and it started to do it again. So it seems to do it when its cold outside. But ill try it again with the A/C on.

[95hardbody]

Assuming you've found no vacuum leaks, I'd next try cleaning the throttle body good. It's free and easy to do. It may or may not cure the problem, but it couldn't hurt.

I also assume that on your vehicle (like my truck), when the A/C compressor engages, the throttle "kicker" extends a little bit to keep the engine from dieing if you're at idle or low vacuum or something...it extends to crack the throttle open a bit more. Knowing that your problem occurs both when this is happening and when it's not happening, it actually doesn't seem to be a problem with the idle control system...unless the kicker motor is sticky and moves irratically, but I doubt that'd be the case (check it anyway).

Also common on the trucks is a broken wire to the IAT sensor (Intake Air Temperature). Without this, you sometimes get a rough idle. That should throw a computer code, though, and light the MIL. Aside from what I've mentioned above, I'm kinda running out of ideas.

[knight_240]

ill cheak it out! thanks for your help

[Rev_D21]

IACV valve may be taking a squat on you. I have read that similar symptoms are felt on the Altimas KA24DE, most common problems are the IACV and the Distributor. The ditributor likes to fill with oil and ruin the electronics inside. The IACV will cause an erratic idle when it has failed. They won't always trip a CEL though.

[xxtrizz]

Hey 95Hardbody could you explain a little more abou tthe GM idle speed controller thingy? My 94 pontiac trans port van idle drops and sometimes dies when brakeing to a stop. I cant figure it out ive used sea foam on the intake so im sure the carbon is cleaned out. But technically speaking what should i do to check the idle drop on my van?