Hunt for Idle

[TomCat]

I just had some stereo work done on my 1991 NSX (5 speed, ODBI) (the owner of the stereo shop is a knowledgable NSX owner). I've only had it for three months but I had never had any electrical/battery problems.

When I picked it up I noticed that it was "hunting" for idle...almost dying and then surging. I also got a check engine light. I called the shop and the owner said to pull the negative terminal off the battery for 30 sec and then reattach it...this did not solve the issue but what I have determine:

1) The negative terminal was a little loose...I have shimmed it for tightness.
2) If I start the car and don't touch the throttle it settles down to a perfect 800 rpm idle...if I blip the throttle it starts the hunt!!! almost dying
3) The check engine light has come on during this evaluation phase

The car ran perfectly on the dyno a few weeks ago so I am sure it is something associated with the electricals/stereo.
One stereo tech asked me if I had trouble with the battery staying charged and I said...never even though I have left it sitting for 3+ weeks...they had the car for 10 days.

I'd like to know the procedure for pulling the clock fuse...resetting the computer (if that works for OBDI) and if I need to do this in conjunction with the battery disconnected?
THANKS

 

[Daedalus]

Have you pulled the code? Bet it's MAP sensor.

 

[TomCat]

Have you pulled the code? Bet it's MAP sensor.

Thanks...
Additional info. When the car is cold (high idle) it didn't seem to do this when it warmed up still in my garage (lower idle) it see to start down it. It got more pronounced (almost instantaneously) when I turned the headlights on to take it for a test drive.

It is on a battery tender right now to see if low battery/electrical is causing some strange gremlins...BMWs seem to be especially prone to this.

 

[Daedalus]

True, cars act funny when the voltage drops below some threshhold, but I hope that's not the case. With the car running, the alternator should put out more than enough juice to power everything, including the headlights. Weird sympom though, hunting with the lights on. Have a voltmeter? You can all but eliminate voltage being the cause by measuring across the battery cables with the car running, headlights on. Pulling the code will point you in the right direction, assuming the hunting is linked to the code thrown.

 

[Mirroredshades]

I had the exact same thing happen to me after I had a stereo installed. The installer messed something up. 10 days for an install? I bet he knows it too. Take it back and raise hell.

 

[sjones]

I had the exact same thing happen to me after I had a stereo installed. The installer messed something up. 10 days for an install? I bet he knows it too. Take it back and raise hell.

Do you remember what specifically was messed up in your case?

 

[Mirroredshades]

No. I should have had them uninstall the stereo. I spent several thousand dollars trouble shooting every single electrical gizmo in the car. Eventually it fried the main ecu and I sold the car for salvage.

 

[Whatwasthat]

The computers in our cars have to "learn the idle" after the battery is diconnected for a time period. I can't remember the exact procedure, but you do have to let it idle for a period of time and something about pulling the parking brake. Hope it's an easy fix.

 

[Larry Bastanza]

The computers in our cars have to "learn the idle" after the battery is diconnected for a time period. I can't remember the exact procedure, but you do have to let it idle for a period of time and something about pulling the parking brake. Hope it's an easy fix.

EVERY NSX I service has the battery disconnected. I have never experienced any idle issues upon startup.

HTH,
LarryB