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My car has some gremlins. I would appreciate any assistance or direction in chasing down this problem.

Car: 1993; 3.8L NA; Automatic; 46,000 miles.

Symptoms occur when the car is cold after sitting for an extended period.
Symptoms stop once the car warms-up.

The car runs fine under acceleration, but when i come to a stop I hear a grumbling noise which seems to come from the passenger side and the car slightly shudders.

The symptoms do not change if the A/C is on or off.

Both symptoms go away if i put the car in neutral or accelerate. Again, all symptoms stop, even at idle, once the car has warmed-up.


Other Symptom which may or may not be related:

If a/c is on norm or max, operates fine at idle or cruise. Under acceleration, all air flow moves to the defroster vents. I believe this is a vacuum problem, but do not know if it is at all related to the issue above.

Thanks again for any help or direction.
 

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For the stumble, you'll want to look at the IAC valve. Typically when they get dirty they will not work properly when cold but may once warmed up. You can try cleaning it.

For the vent problem, you have vacuum since the vents operate under no/light load. Your problem is that the vacuum storage tank isn't keeping the vacuum applied when engine vacuum ceases. This could be a disconnected vacuum line, bad check valve, or bad storage tank. Look at the vacuum tee near the A/C accumulator and make sure everything is hooked up and nothing is broken. To check the tank, disconnect the line that goes to the passenger fender area and apply vacuum, then make sure that it holds once you stop.
 

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My car has some gremlins. I would appreciate any assistance or direction in chasing down this problem.

Car: 1993; 3.8L NA; Automatic; 46,000 miles.

Symptoms occur when the car is cold after sitting for an extended period.
Symptoms stop once the car warms-up.

The car runs fine under acceleration, but when i come to a stop I hear a grumbling noise which seems to come from the passenger side and the car slightly shudders.

The symptoms do not change if the A/C is on or off.

Both symptoms go away if i put the car in neutral or accelerate. Again, all symptoms stop, even at idle, once the car has warmed-up.


Other Symptom which may or may not be related:

If a/c is on norm or max, operates fine at idle or cruise. Under acceleration, all air flow moves to the defroster vents. I believe this is a vacuum problem, but do not know if it is at all related to the issue above.

Thanks again for any help or direction.
there is a vac junction (I had this issue on m 91) near the passenger side firewall that may let go. Check all your vac lines under the hood, especially in that area.
 

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Check the white vacuum line under the blower motor on the passengers side. It is placed nicely to allow feet to hit it and knock it loose. I delt with the moving vents and an annoying hiss from the dash for over a year before I found it after having to pull the dash for something else and spotting the little dangling hose.
 
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