Jon97
07-16-2001, 02:38 PM
On three occassions during the past two weeks, I've experienced the following: at the top end of first gear, and on through to second gear, the car makes a loud, low-frequency, almost subsonic "whooping" sound. I can't tell if it's coming from the engine or the chasis. But it's loud and and is accompanyied by a vibration, which is always alarming. The sound is low and loud enough to hurt my ears -- in fact I even wondered if it was due to an air pressure imbalance caused by my open sun roof. Anyhow, the sound/vibration goes away by the time I reach 45mph or so. The sound does *not* occur when I rev the engine at a standstill. And whne the problem is occuring, I don't seem to be experiencing any power loss.
I suspect two possible culprits, and I would like some input on these theories.
1) The problem is wheel/tire related. Can this problem occur when the tires are severely imbalanced? Because the problem seems to occur at a specific rotational speed, I thought wheels/tires might be to blame. But then again, why wouldn't the problem occur every time I drive? Coincidentally, I am getting a full set of SO-2s installed this week, and we'll see if the newly balanced tires make the problem go away.
Or...
2) Could the problem be VANOS-related? Maybe tire-rotation speed isn't the issue. Maybe it's the rev range that's to blame. Can the VANOS system develop a timing problem and then correct itself? The strange thing is that if it is VANOS-related, how come the sound doesn't occur when I'm reving at a standstill? Also, again, I should note that I don't seem to be losing any power during the problem, and one would expect a power loss if VANOS is to blame, right?
I'm stumped. Anyone ever experience the same thing? What was the culprit? Any insight would be most appreciated! Thanks, guys.
I suspect two possible culprits, and I would like some input on these theories.
1) The problem is wheel/tire related. Can this problem occur when the tires are severely imbalanced? Because the problem seems to occur at a specific rotational speed, I thought wheels/tires might be to blame. But then again, why wouldn't the problem occur every time I drive? Coincidentally, I am getting a full set of SO-2s installed this week, and we'll see if the newly balanced tires make the problem go away.
Or...
2) Could the problem be VANOS-related? Maybe tire-rotation speed isn't the issue. Maybe it's the rev range that's to blame. Can the VANOS system develop a timing problem and then correct itself? The strange thing is that if it is VANOS-related, how come the sound doesn't occur when I'm reving at a standstill? Also, again, I should note that I don't seem to be losing any power during the problem, and one would expect a power loss if VANOS is to blame, right?
I'm stumped. Anyone ever experience the same thing? What was the culprit? Any insight would be most appreciated! Thanks, guys.