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Old 4th November 2018, 11:31 PM
gsp1337 gsp1337 is offline
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Join Date: Mar 2017
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Default 1997 A8 4.2L idle problem when cold, interchangeable part #?

Hi! For the past two winters, I've had a very peculiar problem with my A8. Whenever the temperature was below -15 degrees C, the car wouldn't start due to the idle valve, so I replaced it with a used one.

Now the used one would start up fine, drive fine for about a minute or so. But after that, every time I would lift off the throttle, the revs would jump up a bit (kind of like it was stuck on cold idle) and the car would start gaining speed. As you can imagine, this wasn't the funnest situation in the snow, especially while trying to stop. It also made the shift pattern erratic. When I would put it in park, it would sometimes idle at 2500 to 3000 rpm. Again this is in the cold, usually below -15. When the ambient temperature warmed up it was fine. Obviously I couldn't keep driving like this so I threw in my old one again, this time just giving a bit of throttle when i starting it. Lately, the original idle value is starting to do the same thing as my replacement one (revving high while driving while off throttle).

I have zero problems starting and driving the car during the summer weather.

Now the part # I used is 077133455C (original one and used one purchased).

My question is if any idle valves with the part numbers 078133455B or 078133455A would work? They essentially all look identical, but they only list the 2.8L from the A4. Unfortunately the latter part numbers are a bit cheaper new than the 077133455C.

Im not sure if any of these part numbers are replacements of the older versions. I just haven't been able to find any information on it.

Any other input is greatly appreciated.


Thanks.
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