'93 Buick Park Avenue, 3.1
The complaint is an intermittent jump from idle to high rpm. I wasn't able to duplicate the symptom on a test drive but the Service Engine Soon light was displayed during the short road trip. A test for engine codes with a scan tool could shed some light on the problem.
I have an old OTC 4000 Enhanced that is my tool of choice for these earlier systems but since it doesn't get used much these days it was easier to just grab the Snapon Solus Pro and give it a try. The scan tool would not communicate with the car's computer. Now before you go into diagnostic mode, faced with a communication problem, try a different scan tool. It isn't unusal at all to find a particular tool doesn't read a particular system well. That's life in the aftermarket scan tool world. The OTC EVO worked fine. My stored trouble code was a 22. I guess no need to dust off the 4000.
A 22 sets if the engine computer sees a voltage of less than 0.2 for at least 4 seconds on the throttle position sensor signal circuit. Before digging out the multimeter and doing tests, and since the scan tool is already connected, I can pull up the datastream and look at the tps voltage as seen by the engine computer. In this case it was 0.04 volts with throttle closed and key on. The voltage did rise with opening the throttle but that voltage is out of range. Now since the throttle sensor connector is not hard to access, I disconnected the sensor. At the connector you should have a 5 volt reference on the gray wire. So if you jumper the gray wire to the blue, which is the sensor signal wire, and you see the sensor signal voltage on the scan tool data change to 5 volts you know you have 5 volts to the sensor and that the wire from the sensor to the computer is good. A 5 volt sensor signal voltage should also set a code 21 (voltage too high), which will verify the computer is good.
After doing the tests and verifying the throttle position sensor was bad I replaced the failed part and fixed the problem.
Kenneth Hayes
deranger@ipa.net
