1987 Delta 88 idle problem

[87delta88]

I have a 1987 Olds Delta 88 RB with the 3.8L odd fire V6 and 4 spd auto w/OD, 142000 miles.

At idle the engine runs very rough. With the lights and AC on, the car will sometimes die when slowing down from 55+. It has also died while idling, with both lights and AC on.
The voltmeter will range from 12-14 VDC at idle, but stay close to 14 when driving. The AC works fine.

There are no codes that come up on the diagnostic test.

The spark plugs are two months old, though the plug wires are a couple years old (I think).

Thanks!

[W-44Olds]

Hmm... How is it when you first start the car ? Is it fine or do the same thing ? Or does it only do it once the car has ran awhile ?

[87delta88]

It does it whether it is hot or cold, though it is worse when cold.

[SQUAREMAN81]

Try changing the throttle positioning sensor located on the main throttle boddy. I recently had this problem.