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Car dies when I take my foot of the clutch - Help!

 
Old 02-04-2019, 11:59 AM
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ARC Driver
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Default Car dies when I take my foot of the clutch - Help!

Hello,

About three weeks ago I removed the AC compressor belt from my 993 and about a week later I unhooked some power cables for accessories from the battery that previous owners installed. The car than sat for about a week after that. Yesterday I charged the battery and tried to take it for a drive. When I start it up it idols fine but when I take my foot off the clutch while driving it dies. I restarts just fine but once I take my foot halfway off the clutch it dies again.

What could be causing this?

Last edited by ARC Driver; 02-04-2019 at 02:26 PM.
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Old 02-04-2019, 03:52 PM
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NC TRACKRAT
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To my limited knowledge, the only thing electrical affecting clutch operation is the clutch microswitch in the pedal cluster. You may be able to start the vehicle with the clutch depressed but it might be shorting out when you try to raise the pedal. However, I always thought that, once a signal was received that the clutch is depressed, the car starts and microswitch is no longer in the circuit. I would remove the wooden floorboard and have a look. There's a thread about by-passing the microswitch which many of us have done. (See note#4 in the recent thread here: https://rennlist.com/forums/993-foru...-rebuild.html. It also refers to other threads on the same subject.)
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Old 02-04-2019, 04:24 PM
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Originally Posted by NC TRACKRAT View Post
To my limited knowledge, the only thing electrical affecting clutch operation is the clutch microswitch in the pedal cluster. You may be able to start the vehicle with the clutch depressed but it might be shorting out when you try to raise the pedal. However, I always thought that, once a signal was received that the clutch is depressed, the car starts and microswitch is no longer in the circuit. I would remove the wooden floorboard and have a look. There's a thread about by-passing the microswitch which many of us have done. (See note#4 in the recent thread here: https://rennlist.com/forums/993-foru...-rebuild.html. It also refers to other threads on the same subject.)
Thanks, I'll check it out.
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Old 02-04-2019, 04:59 PM
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Clean the Idle Stabilization Valve and also drive the car. The ECU learns over time and will adapt slightly to the changes you've made.
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Old 02-04-2019, 05:53 PM
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Originally Posted by ARC Driver View Post
I unhooked some power cables for accessories from the battery that previous owners installed.
What accessories did you unhook?

An alarm system and ignition cut-off wired into the vehicle's system?
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Old 02-04-2019, 06:06 PM
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I would purchase one of those $4 volt meters that plug into the cigarette lighter socket and observe the voltage. It should be 13.5 to 14.5 volts with the car running and over 12.5 volts with the engine just turned off.
If a short in the peddle cluster is serious enough to shut down the DME and stall the engine the meter should clearly show a sudden voltage drop well below 12 volts.
https://www.ebay.com/itm/Digital-LED...Vg24:rk:9:pf:0
If you are speaking of it stalling at the clutch engagement point in the peddle's travel something causing low torque at idle or just off idle may be your issue.
Andy
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Old 02-04-2019, 07:09 PM
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That one I hooked back up. The rest appear to be associated with an amp, speakers, and a charge cable and microphone that were installed in the cabin.

That black cable for the alarm is the only thing I have I have hooked up to the battery other than the neg and pos terminal clamps. Does that sound correct?
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Old 02-04-2019, 07:09 PM
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Originally Posted by IXLR8 View Post
What accessories did you unhook?

An alarm system and ignition cut-off wired into the vehicle's system?
That one I hooked back up. The rest appear to be associated with an amp, speakers, and a charge cable and microphone that were installed in the cabin.

That black cable for the alarm is the only thing I have I have hooked up to the battery other than the neg and pos terminal clamps. Does that sound correct?
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Old 02-04-2019, 07:11 PM
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Originally Posted by pp000830 View Post
I would purchase one of those $4 volt meters that plug into the cigarette lighter socket and observe the voltage. It should be 13.5 to 14.5 volts with the car running and over 12.5 volts with the engine just turned off.
If a short in the peddle cluster is serious enough to shut down the DME and stall the engine the meter should clearly show a sudden voltage drop well below 12 volts.
https://www.ebay.com/itm/Digital-LED...Vg24:rk:9:pf:0
If you are speaking of it stalling at the clutch engagement point in the peddle's travel something causing low torque at idle or just off idle may be your issue.
Andy
Thanks I'll get one of these.
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Old 02-04-2019, 07:13 PM
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Does this sound like it could be a fuel pump issue? I feel like the issue wouldn't be related to removing accessory cables or the ac compressor belt, even though I wasn't having the problem before.

Would letting the car idle for a while help to sort things out?
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Old 02-04-2019, 07:14 PM
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Originally Posted by Churchill View Post
Clean the Idle Stabilization Valve and also drive the car. The ECU learns over time and will adapt slightly to the changes you've made.
With the car dying on me over an over again, will it damage it to drive it around?
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Old 02-04-2019, 07:16 PM
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Originally Posted by ARC Driver View Post
That black cable for the alarm is the only thing I have I have hooked up to the battery other than the neg and pos terminal clamps. Does that sound correct?
I don't know, not being there to diagnose.

I'm just saying that if the previous owner or installer knew his electronics, he may have wired it with a relay so that it does start as it should and does, but cuts out when the clutch is released.

Your car must be a 1996 or newer unless the installer modified it.
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Old 02-04-2019, 07:22 PM
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Originally Posted by ARC Driver View Post
Does this sound like it could be a fuel pump issue?
But it could be a DME issue. I have seen enough of these with terrible solder joints. If the solder joint heats up, its enough to break the circuit.

Kind of coincidental that it would fail during your electrical clean up.
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Old 02-04-2019, 07:42 PM
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Originally Posted by IXLR8 View Post
I don't know, not being there to diagnose.

I'm just saying that if the previous owner or installer knew his electronics, he may have wired it with a relay so that it does start as it should and does, but cuts out when the clutch is released.

Your car must be a 1996 or newer unless the installer modified it.
It is a 1996, how did you know?
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Old 02-04-2019, 07:48 PM
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Originally Posted by ARC Driver View Post
It is a 1996, how did you know?
That is the 1st year of the clutch interlock.

You should Google and download the electrical schematics to see what is involved with the interlock.
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