Does the ECM use the TPS output when the motor is cold (closed loop)?

 

I'm going to say yes because the one I bought back in the spring/summer went out a few weeks ago causing the car to run like crap on a cold start and was throwing a high voltage code almost instantly.

 

Computer always uses TPS output. And FYI closed loop only happens once the motor is warmed up. Open loop is for cold.

Are you having a problem? Or just curious?

 

I have a definite problem. Engine has a very erratic idle when cold. Varies between 500 and 2000 rpm. The dirveabity of the car when cold is terrible. It moves a few feet about stalls goes a little further and does it again until it reaches about 45 and ten soothes out some. Idles and runs almost right when warm. I have replaced the fuel filter and EGR solenoid. Engine vacuum is a steady 17 lbs. Repair shop replaced the computer, IAC and colant temp sensor connector. They are at a loss of what to do now. I am tring to learn more to fix the problem

 

Does the 'service engine soon' light come on?

Just taking a guess, my first thought would be the TPS (you can test it if you have a voltmeter to see if it has any dead spots) or just replace it, its about 8 bucks where I buy parts. My car did some very funky things similar to what you described when I had a bad TPS.

Let us know what you find!

 

The "service engine soon" light never comes on which seems kind of odd.

 

Try replacing the TPS just to rule it out. It's cheap and you can do it yourself in just a few minutes.

Are both injectors firing nice cones?

Does the SES light flash a few times when you first start the car to let you know it's alive?

Have you checked for vacuum leaks? You can try popping off various vacuum hoses and plugging the port to see if any of that fixes the issue.

 

I was thinking about replacing the TPS.

Both injectors are firing a nice cone but looks like a lot of fuel.

The SES light does come on before starting to do the bulb check.

Engine tests 17" vacuum when idling warm.

Thanks for your ideas.

 

Please expand on almost right when fully warmed up.....?

 

The idle is a just little rough when fully warmed up. Power feels down a little when driving on the highway. I also noticed when driving on highway at 70 mph cruise was not keeping as steady speed as it used to. Would occasionally speed up to 72 and then slow to 68. May not be related.

 

I agree in having your TPS replaced as well, but while your at it, inspect the ignition system, too, especially the ignition module....

Sounds like the cable needs a little adjustment. The last time I ran cruise control in a 3rd Generation F-Body, it either slipped out on it's own after it's setting, or, with the assistance of me hitting the throttle, would immediately reset itself once the set speed was again realized. Rarely ever used it, so I tossed it....