Vibration during idle

[AdamB86]

93 GC Laredo when either at a light and the engine is just slightly below 750 RPM, it begins to sputter and vibrate like crazy. It feels like I'm driving a manual and about to stale out, but this is an automatic transmission. When I begin to accelerate it's really rough and feels like it might stale out until I get to about 1250 to 1500 RPM and then it's fine again. I was having problems with it starting last year so all the spark plugs have been replaced and the carbon buildup in the engine was cleaned out. I am thinking maybe the throttle body might be dirty but I haven't checked it out yet.

Any suggestions?

Thanks

[BenBB]

Yea check the throttle body, it also could be the IAC valve.

[AdamB86]

The throttle body is clean as far as I can tell. I have a guide from the Haynes Repair Manual to check the IAC so I'll try that and see if it's the IAC.

EDIT: Tried it, but today it didn't do it at low RPM. I drove it a few miles to get the engine warmed up, but it didn't vibrate at the stops. Maybe I can try again tomorrow after a trip to school.

[MAldrich]

Originally Posted by AdamB86

93 GC Laredo when either at a light and the engine is just slightly below 750 RPM, it begins to sputter and vibrate like crazy. It feels like I'm driving a manual and about to stale out, but this is an automatic transmission. When I begin to accelerate it's really rough and feels like it might stale out until I get to about 1250 to 1500 RPM and then it's fine again. I was having problems with it starting last year so all the spark plugs have been replaced and the carbon buildup in the engine was cleaned out. I am thinking maybe the throttle body might be dirty but I haven't checked it out yet.

Any suggestions?

Thanks

Hey bud, I had the same problem and I found out I had a burnt exhaust vale and it was only kicking on 5 cyl.s Got a new head and it runs like a beast now...have your compression checked.

[AdamB86]

Originally Posted by MAldrich

Hey bud, I had the same problem and I found out I had a burnt exhaust vale and it was only kicking on 5 cyl.s Got a new head and it runs like a beast now...have your compression checked.

Alright I'll remember that when I get time to have it looked out in a few weeks. I bought a can of carb/throttle body cleaner and it was dirtier than I thought. Cleaned it up and it's been running great since. Knock on wood.

[MAldrich]

Glad that helped, maybe valves are ok..

[AdamB86]

Originally Posted by MAldrich

Glad that helped, maybe valves are ok..

Who really knows. I just spent 1500 on various brake repairs in the last two months so if cleaning the throttle body up fixes it I'm a happy camper. I must realize that it is 13 years old and it did sit for two years before I got it, so things are popping up now.