Throttle switch question.

[cano944]

Does anyone know what happens when a throttle switch goes bad?

[Roger Hall]

I can only tell you what I have read in other posts. Since the TPS (throttle posistion switch) is underneath it somtimes get filled with gunk. The electronics do not use the TPS input when the engine is cold so you would not notice a difference durring warm up. Once the engine is warm the TPS adjusts the air fuel mixture. The best way to measure it is with an air/fuel mixture guage. You might not even notice small problems while driving. If the problem is bad enough then there are four possibilites.

If the TPS is not richening the mixture then you are probably running very lean under acceleration. This would cause poor acceleration, and possibily show up more in the upper RPM range 5K and above.

If the TPS failed at full throttle then you would probably notice blck smoke comming from the exhaust, poor gas milage and possibly a jump in acceleration as the RPM's rise. Somewhere around 3500k.

If the TPS fails at partial throttle then you probably wont see many symptoms.

If the TPS is sticking between these three settings you will probably notice some surging and a mixture of all the problems.

Since the TPS is difficult to get too, and since these symptoms can be caused by many other problems I would first make sure that the air intake is functioning properly. There is a flap that can stick, also make sure there are no vacuum leaks, and that the air filter is in good shape. In addition I would also run some fuel injector cleaner through the system and change

Fuel filter
Spark plugs
Distributor cap
Rotor
O2 Sensor

I would also check the spark plug wires.

[cano944]

Thanks,I am in the middle of changing the oxygen sensor.It's a matter of finding the right part.I think according to what you say symptoms are for a bad throttle switch,mine is bad,almost for sure.When I got the car the guy gave me an extra(used),which I think he never got around to installing.I will do a quick part swap to see what happens.I am also doing the wires,cap/rotor,fuel filter.I am definitely not feeling a smooth powerband now.

Chris

[Roger Hall]

You can use the generic Bosch O2 sensor. Try this site for info

http://frwilk.com/early944/misc/oxygen.htm

[cano944]

I ended up getting the Borg-Warner for $95 shipped.

[ronin]

good looking car, btw

[CJFusco]

"...and possibly a jump in acceleration as the RPM's rise. Somewhere around 3500k... If the TPS is sticking between these three settings you will probably notice some surging."

aren't these the symptoms of owning a 944?