I have no idea what could be causing this but I will try to explain it as best I can. Here's a typical situation: At night, usually when the temperatures start to drop, I am driving home on the highway cruising at about 80 mph running at around 2000 rpm and the rpm's tend to jump around slightly after about 5 minutes worth of driving. Usually the rpm's go from 2000 to 2500, a constant bouncing back and forth real quick and then it goes away. I don't have this situation during the day, only at night or early in the morning. I would think that if the cable needed to be adjusted, the rpm guage would act up throughout the day, not just at certain times. The main thing is is that the car does not feel like it loses power, the needle just jumps, but never dips below where it should be. This is more annoying than anything else. Has anyone had an similar problems or know of anyone with this ghostly "rpm jumping"?

I have an 87' T/A, 305 TPI, 700R4 trans.

 

Check the connections to the coil and see if any are loose. I had a loose connection from my ECM to the coil wire and it did that.

 

Yes, I have had this problem and it was the TPS sensor. Tech articles off this sites main page will tell you how to check it. If it tests bad, remove it, work the wiper arm back and forth, LOTS, spray it down with carb cleaner (LOTS), work it some more, wipe it down and reinstall. Test it again, that fixed mine, the wiper arm that sets up the resistance to produce the dc voltage gets flat spots on it, dirty contacts, which makes the computer trip out because it can't tell where the throttle is.

 

Thanks, I'll check both the coil and the TPS sensor and let you guys know.

 

I solved my bouncing with a new cap and rotor. The old one (OEM, 75K miles and 14 years) had started to grow deposits on the aluminum terminals under the cap. Everything metal under the cap on the distributor was badly rusted, but the new cap and rotor seemed to do it.

I also put in new plugs and wire (once again, this car had never had a tune up). I also unplugged the wires to the coil thinking I would upgrade to an MSD coil, but I left the stock one in there, so it's possible that might have done it to.

Try any of the above, but I think the new cap and rotor are really what helped me the most.