Cold Start Problem
11-26-2005, 01:29 PM
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Cold Start Problem
I know this is a FAQ, and I've searched, but I'm still having a problem narrowing the cause.
Stock 2000 A4 1.8TQ, 108k miles.
Cold starts, after sitting overnight, are very difficult. The engine cranks, but ignition is a problem. After several cranking attempts, car will eventually start, run rough for a few seconds, and then smooth out. Immediately after the start, the smell of raw gasoline is usually present. Warm starts during the day are no problem. Car performance is fine once it's started. Pulled engine fault codes with VAG-COM, and there are none except for an intermittent cruise control code.
I suspect that the battery may need replaced because the car cranks more slowly than I think it should--but it never fails to turn over. However, because it turns over, I'm not sure how the battery could be at fault.
One thing that is missing is the spin-up of the secondary air pump. Previously, the secondary air pump would activate immediately after startup, and occasionally when idle. It doesn't seem to activate at all now, though I'm not sure if ambient temperature plays a role or not. In any case, there are no engine fault codes pointing to the secondary air pump, so I assume that it's not being activated for some reason--not because it failed.
Did a quick check for vac leaks, and didn't see or hear anything obvious, though I assume that I'd get a fault code for a consistent lean condition at some point if the leak was big enough.
Does anyone have any ideas?
Thanks,
JKG
Stock 2000 A4 1.8TQ, 108k miles.
Cold starts, after sitting overnight, are very difficult. The engine cranks, but ignition is a problem. After several cranking attempts, car will eventually start, run rough for a few seconds, and then smooth out. Immediately after the start, the smell of raw gasoline is usually present. Warm starts during the day are no problem. Car performance is fine once it's started. Pulled engine fault codes with VAG-COM, and there are none except for an intermittent cruise control code.
I suspect that the battery may need replaced because the car cranks more slowly than I think it should--but it never fails to turn over. However, because it turns over, I'm not sure how the battery could be at fault.
One thing that is missing is the spin-up of the secondary air pump. Previously, the secondary air pump would activate immediately after startup, and occasionally when idle. It doesn't seem to activate at all now, though I'm not sure if ambient temperature plays a role or not. In any case, there are no engine fault codes pointing to the secondary air pump, so I assume that it's not being activated for some reason--not because it failed.
Did a quick check for vac leaks, and didn't see or hear anything obvious, though I assume that I'd get a fault code for a consistent lean condition at some point if the leak was big enough.
Does anyone have any ideas?
Thanks,
JKG
11-26-2005, 02:52 PM
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Re: had the first problem and it turned out to be the battery
Check the coolant temp sensor reading in the measuring block if you can, make sure it is reading the outside temp after car has been sitting. These things are a problem, especially if you have the old black coolant temp sensor (located on back of cyl head).
Maybe clean the throttle body as a precaution, even if it isn't the cause it can save you from later problems. If the ecm thinks the engine is
100 and its 40, the car will be slow to start and ran crappy. You can wiggle the sensor while looking at the measuring value block and see if it changes.
Maybe clean the throttle body as a precaution, even if it isn't the cause it can save you from later problems. If the ecm thinks the engine is
100 and its 40, the car will be slow to start and ran crappy. You can wiggle the sensor while looking at the measuring value block and see if it changes.
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