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Northern, CA
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Annoying Deceleration Lurch
I have an '89 Carrera with what appears to be a very sensitive fuel cut-off/deceleration mode. I had an '87 Carrera several years back but don't remember the "lurch" when letting off the throttle being as bad as the '89.
It's very annoying when the throttle is nearly closed, but not completely, such as cruising through town at a slow speed in traffic. The car can't seem to make up it's mind if it wants to go into fuel cut-off mode or not and kind of lurches back and forth. It seems to be worse when cold. Can this be minimized by playing around with the idle switch/linkage mechanism or is it one of the "just live with it" traits. |
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07-02-2010, 12:47 PM
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1980 911 SC
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I don't know anything about an '89 or the fuel cut off mode, but , the symptoms you describe are exactly what my SC would do before I replaced the tranny mounts. At very slow speed, in 1st gear, it would "bounce" or "lurch" and not roll along smoothly. I replaced the mounts and now it will idle down the road with out the annoying bounce.
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Life's a Beach |
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07-02-2010, 01:00 PM
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Registered
Join Date: May 2009
Location: Vancouver, BC
Posts: 348
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Do you mean when you let off the gas pedal while driving at slow speeds (such as in stop and go traffic) and your head lurches forward and nearly hits the steering wheel? This is what my '86 Carrera was doing until I found all the vacuum leaks, plugged them and then reset the air/fuel mixture and idle. Now when I let off the gas the car "glides" forward and doesn't cause my head to slam forward on deceleration anymore.
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"Charlie don't surf!" |
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07-02-2010, 05:58 PM
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Northern, CA
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Not That Bad
Mine is not quite that bad. It happens when the throttle is just about to fully close but you're trying to maintain a steady speed.
I believe the Motronic system is designed with some kind of deceleration map to increase fuel efficiency at closed throttle. Mine just seems too sensitive. With the throttle just barely cracked, the car seems to pulse. It's not extreme. Just noticeably annoying. I thought maybe someone knows about a linkage adjustment that might help. |
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07-02-2010, 06:36 PM
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Registered
Join Date: Jun 2010
Location: Loeken, Norway
Posts: 95
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I have the same issue on my 79 SC.
Wasn't 100% sure how to go about searching for the problems. Now I have some things to check out! On the other hand, not much of a problem, can easily live with it. Thanks.. Cheers, Jarle |
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07-02-2010, 09:20 PM
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Registered
Join Date: Jun 2010
Location: Loeken, Norway
Posts: 95
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Quote:
 My 3.0 SC has been running a bit uneven, lurching a bit on low revs while deaccelerating or at low throttle conditions. Especially when cold. Without this in thought, I decided to drop the cat, to get more sound and a bit more hp. And suddenly the problem was gone as well as getting more hp and more power. Probably the 31 year old cat had started to colapse or something.. So, little tip for those with this problem.. Cheers, Jarle |
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07-25-2010, 01:03 PM
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911SC
