I have a 2002 Audi A4 1.8T, my problem is sometimes when I start it the car will not go into high rpm (1200 RPM), instead it just stays at 750~800 or something. This happens only in freezing temperatures, and for a second or two will run really rough and then everything is fine. As I said this happens only when the car is cold and when outside temperature is on the freezing mark.
I am thinking this might be cold start sensor but I don't even know where it is nor how to find it.
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Re: 1.8T with cold start problem.
The engine temp sensor is located at the back of the engine above the gearbox. It is usually green with 4 wires if there is only one sensor, or 2 wires if there are 2 seperate sensors. make sure engine is cold, remove plug, then slide clip out and pull sensor free.
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I've seen from 500 to 1500 RPM in all the manuals I've been through, depending on the year and application (truck/car). In personal experience, 650-800 RPM is acceptable warm operation range. This will also depend on elevation. Will go up to 1200-1500 RPM for cold starting. I live at about 2000ft and my '86 Pickup 22RE idles at 725-750 like a top after about a 3-4 min warm up @ 1250 RPM if it's cold (<45ish).
the iac probably has carbon built up around it this controls the idle speed try cleaning it first,if not it could be a bad iac or a vaccum leak that the iac takes some time to compensate for to control idle.
I have a 99 a4 and it revs to about 1200 at first start, after a minute or so it lowers to about 750 rpm which is the norm.It has done this since it was bought. Also when the air condenser/conditioner is on it idles high. The condenser is run off the engine so i also lose a few horsepower.
I'm not sure what "transmission pulls when changing" means though, needs clarification.
I had the same issue with my '05 A4 1.8T. Turns out it was the RPM sensor. Audi tried to tell me it was teh fuel pump and the cam-shaft positioning sensor. Paid for teh fuel pump replacement and it died 6 blocks from the dealership. Then they replaced the RPM snesor, works great now... Except it's still an Audi.