Engine Braking - odd symptom
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Intermediate
Joined: Apr 2007
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Engine Braking - odd symptom
'89 C4 57k miles.
When decelerating while in gear, clutch engaged, foot off both the gas and brake, engine braking occurs as expected for, however as RPMs drop the car will momentarily speed up - like a slight throttle blip - then continue decelerating. If the RPMs are high enough, I might experience 3 or 4 of these slight throttle blips even though I'm not touching the gas pedal.
Can this be a problem with the ISV??
When decelerating while in gear, clutch engaged, foot off both the gas and brake, engine braking occurs as expected for, however as RPMs drop the car will momentarily speed up - like a slight throttle blip - then continue decelerating. If the RPMs are high enough, I might experience 3 or 4 of these slight throttle blips even though I'm not touching the gas pedal.
Can this be a problem with the ISV??
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Joined: May 2002
Posts: 3,605
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From: Bologna, Italy
It could be a broken throttle return spring or sticking throttle cable? There should be a spring that returns the throttle back to idle once you take your foot of the accelerator. Perhaps if this is broken, the throttle isn't returning to idle properly.
If you look in the engine bay it's a spring next to the end of the throttle cable. This set up is only on the earlier 964 engines and unfortunately I don't have a photo of it to show you - maybe someone else will!
If you look in the engine bay it's a spring next to the end of the throttle cable. This set up is only on the earlier 964 engines and unfortunately I don't have a photo of it to show you - maybe someone else will!
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Joined: May 2007
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From: Portland, Oregon
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Joined: Dec 2010
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From: Ocala, FL
Seems like you could rule out the idle microswitch if you do your usual engine braking but keep the throttle slightly depressed, as if you were attempting to run the engine at 1000 rpm or so. This would keep the microswitch from activating and if your car still behaves poorly, then you can probably rule out the microswitch.
