1999 Pontiac Grand Am

MTOWNBBALLER20

MEMBER
1999 PONTIAC GRAND AM
4 CYL
FWD
AUTOMATIC
127,000 MILES

Hi, my 99 grand am has the normal wear and tear on it, but one thing is the SHAKING when I am at a red light, or anywhere sitting in gear. The rpms are 500-550. Sitting at the red light or wherever, if I turn the ac/heat on or just the fans the rpms will do a sudden drop and then level out to about 500. Also if I decide to turn the wheel while im sitting the rpms drop again.. Ive done a tune up. Replace ignition coil housing. Boots. Oil. Air filter. What could be the problem? Please help.

Also. This problem might be related to the one above. Driving the normal speed limit the car rides fine. Get on the interstate and around 55-60 the car shakes REALLY BAD. But if I increase gas it stops shaking. And also while driving at any time. When I let off the gas. The rpms drop all the way down to the idle rpm. Causing the car to slow down instead of just coast. Is this normal.I dont think the rpms are just to drop suddenly like that as soon as I let off the gas.

1 Reply

OBXAUTOMEDIC

MECHANIC
3,711 POSTS

Hello,

As far as the Shake while sitting still. Check the Engine and Transmission Mounts.

The shake at 55 - 60 have wheel balance checked.

Now the RPM's. When turning the rpm can drop a little. It can also drop when you turn on the A/C. Then all will balance out pretty quickly.

Now, anytime you let of the gas the RPM's will drop down to engine idle, because you are not giving gas to the engine. In turn the Vehicle will start slowing down. So, Yes it is normal.