Had what I thought was an incident

[BMWDavid]

I've had my '89 3.2 for over two years now and have driven over 7,000 very enjoyable miles.

I use the cruise control quite often when driving on divided highways (helps with the speeding!). Anyway I came up on my exit and always in the past I tap the cruise control lever to cancel the setting. This time with out really giving much thought I pushed in the clutch and moved the trans into neutral without touching the cruise control lever.

I was coasting down without touching the brakes...and I let the clutch up. Yeeowzaa! Instant high revs, I saw the tach needle flying up over the top down toward the red zone. Total confusion on my part but I instinctively pulled back on the cruise lever. I thought that perhaps one of the switches on the pedals were not working but after reading the owners manual under the cruise control heading it warned not to do what I just did.

Man...you would think that any clutch pedal action would cancel the setting.

Anyway, heart rate is back to normal and thinking about it I realize that no damage was likely as the rev limiter would have prevented an over rev.

David

[wilke3169]

On the '92 964 you can actually shift and the speed returns to your setting. I was a bit suprised as you were but thankfully discovered it on an upshift.
It is a quirk I guess and as you said, your rev-limiter likely prevented any damage, but a less skilled driver may panic and not react the way you did.
We live and learn with these cars...

[Zeke]

My clutch pedal does not cancel the cruise. I don't think the Boxster does either.

What you did seems like a peculiar way to drive, but we all do different things I guess to break the monotony.

[mossguy]

Milt - You have an Email.

Tom

[Formerly Steve Wilkinson]

All cruise controls are canceled by brake or accelerator action, as far as I know, and not clutch movement. But then I never use cruise control (don't have it on either of our Porsches, but there is one on the Volvo) so what do I know?

[spuggy]

Originally Posted by Formerly Steve Wilkinson

All cruise controls are canceled by brake or accelerator action, as far as I know, and not clutch movement.

Don't have cruise on the 911, but factory cruise on an '86 944 was smart enough to do the right thing when the clutch was depressed.

[aj88cab]

David,

Your '89 (I am assuming it is a Carrera not a 964) has a clutch activated CC switch that needs to be adjusted properly or it could be bad. However, a bad or mis-adjusted switch usually prevents the CC from working in the first place, but it could cause the issue you have if the switch is stuck. The clutch switch is located in the center tunnel next to the gas pedal.

The clutch switch operates a relay (#3 from windshield on front relay panel). That relay may be bad or sticking.

The CC is also turned off by braking. In the case of a Carrera it is a signal from the brake light circuit. If your car suffers from the classic Carrera "slow brake lights syndrome", then that might be part of the problem also. Replace the brake light switches (or the entire master cylinder with new switches if the car has high miles.)

I don't believe it is normal operation for the Carrera CC to return to speed after a clutch operation unless you press the control lever down ("Reset" position). Other models may be different.

FYI - The '88-'89 Carreras used an electric CC Servo (not vaccum). After examining the diagrams for those and previous years, it appears that the Troubleshooting guide in the Bentley Manual (p. 960-12) may not be correct as far as the terminal numbers are concerned for the '88-'89 models. Does anybody else concur?

Good Luck,
Andrew

[BMWDavid]

Originally Posted by aj88cab

David,

Your '89 (I am assuming it is a Carrera not a 964) has a clutch activated CC switch that needs to be adjusted properly or it could be bad. However, a bad or mis-adjusted switch usually prevents the CC from working in the first place, but it could cause the issue you have if the switch is stuck. The clutch switch is located in the center tunnel next to the gas pedal.

The clutch switch operates a relay (#3 from windshield on front relay panel). That relay may be bad or sticking.

The CC is also turned off by braking. In the case of a Carrera it is a signal from the brake light circuit. If your car suffers from the classic Carrera "slow brake lights syndrome", then that might be part of the problem also. Replace the brake light switches (or the entire master cylinder with new switches if the car has high miles.)

I don't believe it is normal operation for the Carrera CC to return to speed after a clutch operation unless you press the control lever down ("Reset" position). Other models may be different.

FYI - The '88-'89 Carreras used an electric CC Servo (not vaccum). After examining the diagrams for those and previous years, it appears that the Troubleshooting guide in the Bentley Manual (p. 960-12) may not be correct as far as the terminal numbers are concerned for the '88-'89 models. Does anybody else concur?

Good Luck,
Andrew

Andrew,

My clutch pedal does turn off the cruise upon depressing the pedal. When pedal is released the cruise resumes. This is correct according to my owners manual. The brake pedal does fully cancel the cruise.

In any case this may be normal but is a bit strange and did catch me off guard for a moment.

David

[aj88cab]

You made me pull out my manual and sure enough there it is...the clutch switch is a monentary CC dis-engage and the engine will return to speed after the clutch is released.

Now that I think of it I do recall a few times having the engine race for an instant, but it had never dawned on me that it was because I went to neutral while using CC.

I learned something new today...a bit embarrassed...having had the car for 5 years...but thankful never-the-less...

thanks
Andrew

[dentist90]

Originally Posted by Formerly Steve Wilkinson

All cruise controls are canceled by brake or accelerator action, as far as I know, and not clutch movement. But then I never use cruise control (don't have it on either of our Porsches, but there is one on the Volvo) so what do I know?

FWIW, my Talon's cruise cancels with a touch of the clutch or brake, but not accel. If I'm cruising along and decide to pass I can simply accelerate in that gear and lift off the gas when complete. The car will coast back down to the set speed and resume. I will often use a light tap of the clutch pedal to deactivate the cruise and keep my foot gently on the accel so there is no abrupt slowing when the cruise comes off. The switch on the clutch is set so that it activates long before the clutch begins to release. I guess the Porsche might be set up to allow changing gears and maintaing the same speed. If true, this arrangement seems a bit dangerous. Say you're coming up to some twisty curves so you drop a gear in anticipation... as soon as you let the clutch out you are accelerating into the curve. Makes more sense to me to require the driver to hit the resume/accel button to reset the cruise.

But my Porsche doesn't have cruise, so what do I know.

[aj88cab]

Originally Posted by dentist90

If true, this arrangement seems a bit dangerous. Say you're coming up to some twisty curves so you drop a gear in anticipation... as soon as you let the clutch out you are accelerating into the curve. Makes more sense to me to require the driver to hit the resume/accel button to reset the cruise.

Ya think!....I was at Barber Motorsports Park once. Came flying into Turn 5 (a 180 degree hairpin), did the heel-toe, downshift thing, but didn't realize I had accidentially hit the CC lever a little ways back. Ya know something... these cars can take a corner a whole lot faster that you realize...

I learned something that day too...!

Actually the core of the problem that day (besides my clumsy fingers) was the "slow brake light circuit" that had allowed me to slow the car but had not disengaged the CC...that was quickly fixed by the way! Definitely something to check in the Carreras.

[kodioneill]

bad design. i connected the clutch cancel wire to the lever cancel circuit. now when the clutch is depressed it sends a cancel to the ecu. you can do it at the ecu harness.