| Thursday, June 23, 2005 |
13:36 - Car Wars: The Phantom Idle Problem
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No real progress on the car front—I called Bob Lewis again yesterday to say that the idle problem still hasn't gone away, even with a) a new mass airflow sensor, b) a new ignition coil, and c) a new battery. They haven't called me back yet. I think they may have filed me under the "crank (shaft)" heading.
I did an experiment yesterday, though. I was heading down a local street on the way to lunch (Taco Bell, again, and the engine idle had jumped from 700 to 1000 at exactly the same point on the route to Taco Bell as it had last time). Noting that the engine was idling at 1000 as I coasted in neutral, I turned the engine off and immediately back on again. The idle dropped straight to 700.
So this tells me that it's not a purely mechanical problem, such as cracked vacuum hoses causing an air leak only when the engine gets hot. It's a very regular step function—700 for the first few minutes, then after being revved up for a bit (and after what seems like a random amount of time), it doesn't drop back down all the way to 700 anymore, but stops at 1000, for the remainder of the drive cycle. This might still be caused by (as CapLion suggested) cracks in some of the vacuum hoses, ones that are only opened up when the vacuum solenoid valves kick on after a certain amount of driving time.
It could also be a bad mass airflow sensor. That was just replaced. Maybe the one they replaced it with is also bad. Or maybe they jostled something nearby loose while replacing it. Neither possibility fills me with confidence.
I just got the comprehensive service manual by Bentley for my car; it's humungous, probably at least 2000 thin pages. But at least I know what's involved in replacing the MAF sensor, now. ('Course, that doesn't mean I'm at all equipped to do it—apparently I need a special tool from VW just to pull out the spark plug wires to get the engine cover off.)
Maybe I should just buy one of these and get it over with.
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Brian Tiemann
