Throttle Position Sensor and Misfire

[badgerraf]

Not sure if I have two different problems here. But I have a 1997 GP GT with the 3800 series and it has begun to misfire at idle. It does this sparatically once it has warmed up and it is just sitting at a stop light. It kicks on the Service Engine Soon light and I read the code on it and cylinder two is acting up. It also says there is a problem with the throttle position sensor. I was planning on new plugs and wires anyways, but could the sensor also have something to do with the misfiring? I understand the concept of the sensor, but how important is it and how does it work? Do you think I have two seperate problems here? Thanks

[richtazz]

Definitely tune it up, including plugs, wires, pcv valve and fuel filter. Have the codes cleared and if the TPS code comes back, you may have an issue with the TPS, but that could be a ghost code caused by the misfire.

[GMMerlin]

Originally Posted by richtazz

Definitely tune it up, including plugs, wires, pcv valve and fuel filter. Have the codes cleared and if the TPS code comes back, you may have an issue with the TPS, but that could be a ghost code caused by the misfire.

A misfire will not cause a "ghost" TBS code.

[GMMerlin]

Originally Posted by badgerraf

Not sure if I have two different problems here. But I have a 1997 GP GT with the 3800 series and it has begun to misfire at idle. It does this sparatically once it has warmed up and it is just sitting at a stop light. It kicks on the Service Engine Soon light and I read the code on it and cylinder two is acting up. It also says there is a problem with the throttle position sensor. I was planning on new plugs and wires anyways, but could the sensor also have something to do with the misfiring? I understand the concept of the sensor, but how important is it and how does it work? Do you think I have two seperate problems here? Thanks

I think you are looking at 2 seperate problems.
Since you have a cylinder specific misfire, I would start there.
Possibility of ignition or fuel related. I would start with ignition because that is the easiest .
You can start by swapping plugs and wires and see if the misfire goes away.
In my experiance with an idle misfire, I would look towards the fuel system (possible lean injector).
With the TPS, it is an important imput to the PCM It is a simple 3 wire potentiometer and diagnosis is fairly straight foreward.
The important thing was the code..was it a performance, low or high voltage code?

[badgerraf]

Originally Posted by GMMerlin

I think you are looking at 2 seperate problems.
Since you have a cylinder specific misfire, I would start there.
Possibility of ignition or fuel related. I would start with ignition because that is the easiest .
You can start by swapping plugs and wires and see if the misfire goes away.
In my experiance with an idle misfire, I would look towards the fuel system (possible lean injector).
With the TPS, it is an important imput to the PCM It is a simple 3 wire potentiometer and diagnosis is fairly straight foreward.
The important thing was the code..was it a performance, low or high voltage code?

It was P0121 Throttle Pedal Position Senson/Switch A Circuit/ Performance Problem. It then says that the computer senses a problem with the throttle circuitry. I agree that I should start with ignition and the cars due for new plugs and wires anyways. The misfire is not continuous so it may be more difficult to pinpoint. I'm not sure if this matters or not. Thanks