Random RPM drop regardless of gas pedal position

[mediccody]

Hey guys, I've got a 1990 Talon TSi with manual transmission, and about 110,000 miles on it. I have had it since June, and the problem which I am about to describe seemed to initially only occur on the highway, but now can occur while I am driving at any speed.

The problem is this: I will have my foot on the gas, usually while accelerating or maintaining speed, when my RPMs drop rapidly. The car behaves exactly as if I were coasting in the gear that I was just driving in, and if I put it in neutral the RPMs go to idle. It seems like more and more often my car rolls almost to a stop on the side of the road before I put it back in first or second and it suddenly begins to respond again.

"Solutions:" (This is in quotations because my friends and I have not tried any actual mechanical interventions yet). Sometimes if I pump the gas, or put the car in neutral, then back in gear, I seem to get a response. Otherwise, if I just keep my foot on the gas, the car will suddenly surge forward again, rise to normal RPMs, and keep going as normal.

A couple of my more automotive inclined friends have suggested that this is possibly due to a faulty throttle position sensor. My research suggests the same thing.

Are all my problems consistent with a bad TPS? Are there any other problems that may be causing this issue?

Thanks

 

[juanpac0]

Ignition issue, check your wires, coil pack and power transistor. My money is on the power transistor (91+ controls output to tach and is why your rpms are jumpy.) If you shift to a lower gear (less load) it'll also fix your issue, for example if its really bad in 5th you can put it in 3rd and itll be more responsive due to less load on the engine (and ignition system.)

 

[3kgt2nv]

also check for cracks in the wires leading to them wich may cause arcing or grounding out the system. motors make a ton of heat and the wiring harness is 21-22 years old in the car.

 

[white92talontsi]

My 90 would randomly cut off on me while driving down the road.
There is a 30 amp ignition fuse on the + post at the battery and on my car it was losing connection.

Also make sure your battery is tied down and not sliding around and hitting the underside of the hood. This will do the same thing and shut the car off.

 

[3kgt2nv]

i had a friend put his battery in the trunk and had an issue with the terminals hitting something and it would shut the car off for a second as it lost ground then it would shudder and stay running.