Glitch or "by design"?
#1
12-06-2005, 09:48 PM
Glitch or "by design"?
My B7 demonstrates some unusual idle behavior. When the outside air temperature (OAT) is above freezing, a routine cold start brings up a 1200 RPM idle. It sticks there for a minute or so and then drops to 800 RPM. The Volkswagen white paper on the design and operation of the 2.0T (a great document, by the way - I have the .pdf file if anynoe is interested) describes this interval as the time required to preheat the catalytic converter.
When the OAT is at or below freezing, I've noticed a different idle behavior. A cold start will result in an idle speed that seems to be reduced from 1200 by some measure of the temperature. If the OAT is 32, it cold idles at about 1100. If the OAT is in the 20s, the cold idle is barely 900. After the usual interval the resulting warm idle is 750 instead of 800.
Is this something that is "by design". I can't think of why, other than perhaps the notion that a 1200 RPM cold idle might unnecessarily stress very cold metal. If this is something that is unique to my car and indicative of a faulty component somewhere I'd like to know so that I can add it to the list of 5,000 mile service items (appointment is next Friday).
TIA
When the OAT is at or below freezing, I've noticed a different idle behavior. A cold start will result in an idle speed that seems to be reduced from 1200 by some measure of the temperature. If the OAT is 32, it cold idles at about 1100. If the OAT is in the 20s, the cold idle is barely 900. After the usual interval the resulting warm idle is 750 instead of 800.
Is this something that is "by design". I can't think of why, other than perhaps the notion that a 1200 RPM cold idle might unnecessarily stress very cold metal. If this is something that is unique to my car and indicative of a faulty component somewhere I'd like to know so that I can add it to the list of 5,000 mile service items (appointment is next Friday).
TIA
#3
12-06-2005, 10:07 PM
RE: Glitch or "by design"?
Yeah, you'd think that would be the case.
It does seem really odd to me. Of course, this is only my 6th aluminum block engine ownership experience and the other 5 have been Subarus. They have a different interpretation of "engineering tolerances" in their engine designs, which is most of what makes them as bulletproof as they are. You can abuse the crap out of a Subie engine and they just take it and move on. My wife once ran one of their 1.8s with NO oil for an entire summer. The car still hung around for 139,000 miles. I sold it because I didn't feel like spending the money to replace the original clutch.
Anyway, I reckon I'll bring it to the dealer's*** attention next Friday.
*** Gratuitous dealer plug - Shneider + Nelson Porsche & Audi of West Long Branch, NJ. They're everything a car dealership should be.
It does seem really odd to me. Of course, this is only my 6th aluminum block engine ownership experience and the other 5 have been Subarus. They have a different interpretation of "engineering tolerances" in their engine designs, which is most of what makes them as bulletproof as they are. You can abuse the crap out of a Subie engine and they just take it and move on. My wife once ran one of their 1.8s with NO oil for an entire summer. The car still hung around for 139,000 miles. I sold it because I didn't feel like spending the money to replace the original clutch.
Anyway, I reckon I'll bring it to the dealer's*** attention next Friday.
*** Gratuitous dealer plug - Shneider + Nelson Porsche & Audi of West Long Branch, NJ. They're everything a car dealership should be.
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