Advise Need - Help Wanted

[NSX4U2]

Have a 97 6-speed tranny. I have the following symptoms:

With my headlights on and approaching a red light I push the clutch in and move the shifter to neutral. The RPM's come down below normal causing the engine to almost stall. The headlights also dim down very low.

Acura is not sure what is causing this. Could it be a sensor on the clutch foot-pedal causing this? Tranny sensor? Bad alternator? Bad battery (starts fine)?

Anyone experienced this before?

Thanks in advance.

97-T #009 @23K

 

[cojones]

I think its related to this problem; however, it may also be compounded by some charging inefficiencies (alternator not getting enough juice, or a short/sink/leak somewhere) in your car.

 

[Nsxotic]

Actually, that problem would never cause the car's rpm's to fall dangerously low to the point of stalling so........ Does it do it when you don't have the headlights on? Try driving it without ANY accessories on.. (radio, lights, etc.) IF it doesn't do it, then it is your alternator. It is not properly charging and once the rpm's fall, the lights are causing stalling feeling. It starts fine now but the battery will fail soon. JMO

 

[NSX4U2]

Thanks for the input. Alternator may be a problem.

Feedback I received includes:

1. Must have fuly charged battery;
2. Check/change plugs;
3. Remove idle/mixture screw from throttle body clean and polish and reset base idle.
__________________________________________
_Hi Larry:

The charging system was something I thought about being the problem also. But since the car starts just fine I assume the battery is fully charged.

The reason I think it is electrical is because it only does this when the headlights are on. The idle does not drop with the lights off.

Is there a switch on the clutch arm (foot pedal) in the car that controls idle speed when more amps are drawn due to the lights on?

It is similar to when you are idling and you activate the power windows. The RPM's drop down slightly.

In my case, the RPM's drop to the point the car almost stalls. And it only does this when I engage the clutch??

IF I SIT AT IDLE (EVEN WITH LIGHTS ON) AND REV THE MOTOR THE RPM'S DO NOT DROP BELOW NORMAL??? HAS SOMETHING TO DO WITH EGAGEMENT OF THE CLUTCH.

Would a spark plug or throttle-body problem be evident ONLY when the headlights are on?

Thanks again for the help.

Regards,

Tom
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[This message has been edited by NSX4U2 (edited 27 January 2002).]

 

[nsxman]

You can rest assured that your problem is electrical and not related to the clutch. Check the specific gravity of battery. Check alternator output. Check regulator. Check major load connections and grounds.

 

[sjs]

Long shot, but...

IF the dimming lights and RPM drop happen only while the clutch it depressed, then look for a dead short in the switch or related wiring that prevents you from starting the engine unless the clutch is depressed.

Such a short would load the alternator, dim the lights, and possibly disrupt the ECU or injectors or ignition due to low voltage, causing the stall.

 

[Kinan]

I would think that any kind of electrical demand great enough to cause this kind of load to a charging system at idle speed would first blow the fuse in its circuit.
The only way to be sure it is electrically related is to measure the voltage drop at the alternator while recreating the problem.

 

[sjs]

Originally posted by Kinan:
I would think that any kind of electrical demand great enough to cause this kind of load to a charging system at idle speed would first blow the fuse in its circuit.
The only way to be sure it is electrically related is to measure the voltage drop at the alternator while recreating the problem.

Probably true, but if the fuse is large enough or defective and the rest of the system is already weak, he may react fast enough that the fuse doesn't blow. The RPM drop could be more about disrupting the computers than the actual load.

Pause…

A quick look at the book and I think it uses the same fuse as the PGM-FI main relay and the Voltage Regulator. Hmmmm… Maybe not such a long-shot after all. Engine compartment fuse #18 (20A) is listed as Security Control Unit, Voltage Regulator (Alternator), PGM-FI main relay. I think the clutch interconnect feeds the Security Control Unit, so even a mild short on that line could disrupt the charging system and the fuel injection.

Mention that to your mechanic and see what he thinks.

 

[NSX4U2]

Thanks again for the feedback. I will relay all possible scenarios you have astutely pointed out.

An NSX tech that I sent a note to seems to strongly believe it is a "base idle" problem.

Regards,

97-T #009 @23K

 

[Amnesia]

My 3000GT had these same problems awhile back.. whenever I hit the clutch so I could shift, the car would stall. With the clutch depressed, the engine will idle if you're not accelerating.. and the idle was too low causing the engine to stall. It was a real pain getting it to the shop... but once there, I had them reset the idle to the factory specs and that fixed it right up.

Hope that helps..

 

[cobalt]

#3: loosen idle mixture trim screw on TB by turning it counter clockwise 1/4 turn at a time, and re-test...should take care of it. after you find the right setting...reset ECU and be done with it.