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Q: Car stalls at idle and fails to restart - 1993 Buick Century

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The car intermittently stalls at idle, and can fail to restart after this. Trying again after results in slow cranking, but nothing else. Sometimes it will start an hour later, sometimes not. It can stall upon placing in drive, and usually sputters so if I keep RPMs high, then ok. Check engine lights have never come on until recent. I'm getting a low voltage to the TPS code. I have replaced CKP sensor, ICM, and MAF. New battery, new fuel filter, the alternator and starter test fine. Replaced spark plugs and their wires. The car gets spark when it won't start. Throttle body and fuel injection cleaning as well. I've detached the Torque converter, but still stalled.

Could this be all from TPS or bad ECM ?

My car has 73000 miles.
My car has an automatic transmission.

Hello and thank you for contacting YourMechanic. The TPS (Throttle Position Sensor) could be a large part of the issue you are having. If there is low voltage to the the TPS, check the harness with the key on and engine off for a 5 volt reference to the TPS harness. If there is 4.5 volts or less, then the ECM has a possible fault. Remove the harness from the ECM and turn on the key with the engine off and see if there is a 5 volt reference to the pin for the TPS harness. If there is a 5 volt reference, then the harness has resistance on that circuit and needs to be replaced. If the reference is 4.5 or less, then the ECM needs to be replaced. If you need assistance troubleshooting the TPS signal, a certified professional from YourMechanic can come to your car’s location to assist with diagnosis and repair of the stalling problem.

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