GeorgeK

I have been chasing a weird anomaly with my car: when I get off the throttle, it seems I get no engine brake, as if the fuel cutoff doesn't work. I can sometimes get the usual "engine brake" by touching the brake pedal, which conforts me in believing the fuel cutoff does not work/works intermittently. I have tested the idle switch with the KTS 300 and it works. I have no stored fault code either.
Any ideas where to look?

2nd question: My car is an '89 C4, engine M64.01. According to the PET, the idle/wot switch is #964 606 019 00. I ordered one, and got something very different from mine, to the point that it can not fit. At all. See pics of mine in the car and the new one with the box. What am I missing??

EDIT see page 2 clutch fork axle support ear brroke off....

Spyerx

can you remove the switches and place on the existing mounts?

GeorgeK

No, plastic studs melted through locating holes.
I'd rather understand where is the mistake and return those for the right ones, but the part number for these corresponds to my M64.01 engine.

Duck

The new part you received looks like one for the plastic manifold. I have a used one that matches yours if you want a used one. Just PM me.

Harry Apps

According to PET, your Pt No is correct. However, the part you have appears to be that for the M64.02 with the Pt No ending in 01. The EU PET diagram is poor but, unusually, there is a better one on the US PET which clearly shows the differences. Time to complain!

Robbrizzle

Have you tried flushing the ISV with carb cleaner?

-nick

Odd combination of symptoms. I can at least confirm that rpm's will hang if the idle microswitch doesn't activate. Good luck!

GeorgeK

Yup, email sent to the seller. In the meantime, I have found a correct one on my mechanic´s shelves, which is a relief. Although, I have checked the switches with the KTS 300, they both work as they should.

Yup. It was dirty but not filthy. Idle is more stable.

Nice way of putting it. When I go down the mountain (every morning to work), and release the throttle in 2nd gear, the rpms will not drop, and I have no engine brake. Hitting the brake pedal briefly will most often "release" the hangup and I get engine braking again. I am stumped so far. Clutch cable is new. Did not change a thing.

...But of course, it has all taken a backseat yesterday, when the clutch fork likely broke off and fell in the bellhousing, locking the gearbox and engine solid. In the middle of the street. At 6.30 in the morning. in -5°c temperature...

Robbrizzle

Crikey, that sounds ugly. I had similar issues which I attributed to the closed throttle microswitch, reasoning that without it functioning, the ISV wouldn't do its stuff. Carb cleaner inside of the ISV and contact cleaner on the connectors for the ISV worked for me. Good luck with the clutch. :-)

alsaab

Hi.

although the clutch will be the number one topic now, you know that, when you put the heating on, fuel cut-off is disabled in order to go on producing heat in the exchangers. I hate that feature but did not find the time to look which wire from CCU to cut.

Alain

GeorgeK

I was not aware of that. Where did you get that info?

In my car however, this symptom has appeared in the last few months and was clearly not here before, so something´s changed,

-nick

I've never heard of that feature either. Sounds plausible. I'd like to hear more too.

user8- The brake pedal contribution is really baffling in this. And sorry to hear about the clutch. Ouch.

GeorgeK

I believe that depressing the brake pedal cuts fuel injection, which is why I think injection does not cut out when I release the throttle, despite a working idle microswitch.

I have arranged for the car to be flatbedded to my mechanic tomorrow. He starts on it monday. On the clutch issue, that is. He will poke his nose around the throttle issue as well.

alsaab

Hi,

I have read about it on a german forum for 911 owners (elferteam.de) a long time before I bought my 964. But it's real. As mine is a Targa, I sometimes put the heating on also after winter when the top is off, and there is no cut-off. If you start w/o heating and put it on during your trip, it's even scaring during the first deceleration, although you (I) know it will happen. Put the CCU back to the blue dot, cut-off is back immediately.

Alain

elbeee964

I've been watching -nick's answers in agreement.

Mine had similar problems as yours except it was bumping the throttle, not brake, that settled my idle down.
Cleaned the ISV with no improvement.
Finally saw my KTS 300-equivalent noting (with the engine off and no one at the wheel) that both WOT and Idle switches were showing 'off'.
Turned out the throttle cable was just tight enough so that off throttle barely made contact with the Idle switch. Sometimes it clicked, sometimes it didn't. And that explained why upsetting the engine by lightly blipping the throttle at idle would randomly make the idle suddenly settle down. (It was just THAT insidiously adjusted so as to make it an inconsistent problem.) Perhaps your braking is similarly upsetting an idle switch teetering at the edge of 'on' off throttle.

Loosening the throttle cable (adjustment nut is along/under the shifter tunnel) took out juuust enough preload on my throttle linkage to consistently engage that Idle switch to 'on', off throttle.
That was many years ago and the problem has never returned on my C2.