Questions and Answers
Century Hesitates And Stalls
Q. I have a 1987 Buick Century 4cyl 2.5 liter with 120,000 miles. I think it has an early model fuel injection system. The engine hesitates and stalls when I step on the accelerator just right. Most of the time it dies when I accelerate to go up a hill. The car runs fine as long as I keep the accelerator constant, but if push it too quickly it dies. I have tried fuel injector cleaner and just recently changed the fuel filter. From other things I have read it sounds like it might be the air filter or the crack angle sensor. What do you think?
Thanks for the help,
JasonA. There are a few things that can cause the problems you are describing. Knowing that system as I do, I think I would take a look at the Throttle Position Sensor (TPS) first. They have been a problem on that engine. It is a variable resistor type and the resistor inside the sensor goes bad after time, leading to the symptoms you describe.
To really test it accurately, you need an oscilloscope, but you can get an idea using an analog (needle type) voltmeter. First thing you can check is the reference voltage. Connect the positive lead of your meter to pin B of the TPS connector and the negative lead to ground. with the key on, It should 5 volts. Now move the positive lead to pin C and slowly move the throttle. There should be a gradual decrease in voltage from the 5 volt reference. At about ½ throttle it should be about 2.5 volts. You need to go very slowly so the meter has time to keep up with the changes.
Another possibility is the Map sensor. Usually when it fails, it will throw a code and light the check engine light.
The best way to test the whole system is to have a scan tool hooked up and make sure all the inputs and outputs are correct. If the system checks out okay and the problem persists, GM has a PROM chip, Part No. 16072835, that will correct the problem.
Information provided courtesy of ALLDATA
