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Idle in stop and go traffic

 
Old 05-19-2003, 10:52 AM
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Niels Jørgensen
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Post Idle in stop and go traffic

Much like I expected my car is now again running as a charm (The recent hesitation under acceleration has once again disappeared - though I'm sure it'll be back ), but this morning another thing caught my attention - I have no idea if it's related or if it's even something I need to be concerned about, but anyway:

In stop-and-go traffic (very slow - never get out of 1st and RPM is less than 1500 RPM), when I depress the clutch and let go of the gas RPM drops violently to ~400 RPM almost stalling the car then rises to 1000 before it stabilizes at 900.

When driving faster (more than 3000 RPM) the car drops to idle much smoother. Quickly down to ~1200RPM, then slowly down to 900 where it stays.

In either case, once it reaches 900 RPM it's rock steady. A small blip of the throttle, however, will send it down to 400 and back up again.

Is this normal?

(BTW: The car has stalled on occasion when coming to a full stop, but it is rare)
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Old 05-19-2003, 11:26 AM
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Could this be an Idle Stabilizer problem?
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Old 05-19-2003, 02:45 PM
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Possible. Is there a way to check the stabilizer? I understand from this <a href="http://www.jdsporsche.com/faq.html" target="_blank">http://www.jdsporsche.com/faq.html</a> that the MAF meter also affects idle, and that it can be adjusted on a pot meter near the fuse panel (mine is an early S4 with no cat).

I recently fiddled with the fuse box so I'm going to follow the above MAF test procedures in case I disturbed something by accident.
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Old 05-19-2003, 02:58 PM
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The only way to check the MAF is with an oscilloscope. I wouldn't mess with the adjustment unless you've checked it first. The idle stabilizer is under the intake and, as far as I can see, the only way to access it is to remove the intake. I suppose you could cut the wires and see whether anything changes and get a diagnosis that way and then splice them together again.
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Old 05-19-2003, 02:59 PM
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The only way to check the MAF is with an oscilloscope. I wouldn't mess with the adjustment unless you've checked it first. The idle stabilizer is under the intake and, as far as I can see, the only way to access it is to remove the intake. I suppose you could cut the wires and see whether anything changes and get a diagnosis that way and then splice them together again.
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Old 05-19-2003, 04:08 PM
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Ok, thanks... I'll start with the basic MAF check (as in "test", don't "touch" ). I don't feel like removing the intake unless there is no way around it.

I'm also going to order fuel pressure gauge and ARM-1 from 928int. - not that it's necesarrily related to the problems I have, but I feel like a blind rat in a maze. I figure the more data I get the quicker I'll find the problems if (when) they appear... Looks like I'll have a couple of busy weekends ahead
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Old 05-19-2003, 04:19 PM
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I'm VERY familiar with the blind rat feeling. You'll figure it out and have a real sense of accomplishment when you do.
Good luck.
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