Engine stalling when clutch is engaged

[midnightgarage]

After the engine gets hot, normal warm temperature, when i go to shift gears as i press the clutch in the rpm goes straight to 0 rpm. would anyone have any idea why?
i do have a supercharger and its been recently re tuned.
things i have done:
Cleaned throttle body
replaced coolant temp sensor
coolant flush
thanks in advance.

 

[Old Guy]

You are a little short on details including such things as the vehicle year and the fuel control. I am presuming that this car is not a drive by wire car since that changes lots of stuff. Also, when you press the clutch pedal in, does the engine actually stall or are you just seeing the tach drop to zero? I am operating on the premise that when you say 0 RPM that means an engine stall.

Once up to operating temperature, does the engine idle at factory specified idle speed when the car is sitting parked and in neutral? If so, does pressing the clutch pedal while the car is parked cause the engine to stall? If it does, there is an input to the ECU (if it is an OEM ECU) from one of the clutch pedal switches that puts the ECU into idle control mode when the clutch is engaged - I believe that it blocks idle control by the ECU when the clutch is engaged. I suggest that you check operation of the clutch input to confirm that the switch has not failed and that the input is correct. Has anybody been messing around with the wiring at the clutch pedal and perhaps screwed up the connections?

Normally, I would not expect the clutch input switch failure to cause the engine to stall. I would expect that it just idles erratically or too low. However, I don't know what the supercharger does to this mix. Are you using the stock ECU with a FIC add on or do you have an aftermarket ECU? If you have an aftermarket ECU and the supercharger re-tuning effort involved changing the fuel settings then perhaps they screwed up the idle control. If you have an aftermarket ECU, perhaps there is no clutch input to check.

When you cleaned the throttle body, did you mess with the throttle position sensor at all (or did the tuning guys mess with the sensor)? The throttle position is one of the inputs to the idle control system and that might be part of the problem. However, if the engine idles fine when the car is parked and in neutral I don't think the TPS is the problem.

When shifting gears, if the engine stalls when you press the clutch pedal in and then you let the clutch pedal out after completing the shift I assume the engine restarts? If so, does the CEL light come on for a couple of seconds like it normally does at start up (if it is an OEM ECU)? If so, that indicates that the ECU lost power when you pressed the clutch pedal so you might have some kind of electrical / wiring problem to the ECU and that problem is somehow initiated by clutch operation .

 

[midnightgarage]

so sorry! i have a 1992 nsx with a gruppe m supercharger.The car is drive by wire.
I am running aem v1 for my engine management.
When the car is warm and I'm in neutral, when I press the clutch in the rpm drops down.
When driving as I press the clutch in and hold the clutch down, the RPM drops all the way down and the engine turns off.
The engine idles at factory spec. no one has been messing with the wiring at the clutch pedal.
When I shift gears and the engine turns off. Once I let off the clutch the car bump starts itself again.
I had the car tuned last year and its been driving fine up until this point. So I don't think its a tuning issue.

Thank for the into so far

 

[Old Guy]

so sorry! i have a 1992 nsx with a gruppe m supercharger.The car is drive by wire.
I am running aem v1 for my engine management.
When the car is warm and I'm in neutral, when I press the clutch in the rpm drops down.
When driving as I press the clutch in and hold the clutch down, the RPM drops all the way down and the engine turns off.
The engine idles at factory spec. no one has been messing with the wiring at the clutch pedal.
When I shift gears and the engine turns off. Once I let off the clutch the car bump starts itself again.
I had the car tuned last year and its been driving fine up until this point. So I don't think its a tuning issue.

Thank for the into so far

Are you sure about drive by wire? A 1991 NSX with drive by wire would be unusual, particularly since I didn't think the AEM V1 supported drive by wire. I thought that drive by wire support only came with the later AEM V2 or the Infinity series. Since the original C30 engine used a conventional throttle cable, have you installed a later C32 engine which uses drive by wire and are you using some kind of separate DBW controller with the AEM V1 to provide drive by wire control or do you have a throttle body adapter to support DBW on the C30? However, none of this probably matters since you really appear to have a system that is definitely not OEM and I can't really provide any advice on specific things to check.

That said, based upon your description of the symptoms it really seems like you have an idle control set-up problem in the ECU. With the engine up to temperature and idling in neutral, pressing the clutch down should not cause the idle speed to drop. I have no direct familiarity with the AEM V1 set up and don't know if and how it would use a clutch signal. The limited aftermarket ECUs that I am familiar with use MAP level, RPM and throttle position as the inputs to determine that the engine should go into idle control mode. The fact that your RPMs drop when you depress the clutch suggests that the clutch switch is connected to something; but, I have no clue as to what that something is doing other than it appears to be doing something wrong.

The fact that the engine dies during shifts also seems like a tuning or ECU configuration problem of some kind. Normally, unless you shift really slowly, the RPM would not drop down low enough for the engine to enter the idle control region so something does seem wrong with the way things are configured.

Unfortunately, since you appear to have a very one of a kind system you are kind of on your own. The best suggestion I can make is to go back to whoever did the gruppe M set-up or did the last tuning round to see if they can fix the problem. As an alternative, perhaps you can find another gruppe M supercharger owner who may be able to advise on the idle control set up. Don't bother trying an Acura dealership. The techs will take one look at the engine and go "what fresh hell is this thing".

 

[Old Guy]

When I shift gears and the engine turns off. Once I let off the clutch the car bump starts itself again.
I had the car tuned last year and its been driving fine up until this point. So I don't think its a tuning issue.

Thank for the into so far

As a final thought, do you have one of those blip shift devices or a blip shift like function implemented in the ECU? I was out driving my NSX earlier today and I noted that during normal shifting, the engine RPM is typically dropping to about 2500 - 3000 RPM (based upon the tach measurement) during shifts. I have a 2000 with the OEM drive by wire system. If your tach RPM is dropping to 0 RPM during shifts, if the idle control function is not screwed up it almost seems like you have an overly aggressive blip shift function that is killing the engine during shifts.