Fuel system?

Tiny
HAMERJAMES
  • MEMBER
  • CHEVROLET
I have a 1994 chevy 2500 with a 4.3 L throttle body injection. It is stumbling during acceleration. I read the codes and got a open circuit on the m.A.P. Sensor. After inspection I found the wiring harness on another sensor right next to the m.A.P, it is also connected to manifold pressure. I reconnected the harness and disconnected the battery to erase the fault. It is still stumbling during acceleration and at a certain engine load also. I tested the map and got 300 ohms on the low side 1300 ohms on the high side. Could it be the t.P.S also?
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Sunday, November 12th, 2006 AT 12:54 PM

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Tiny
JRSIERRA
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Well to check the MAP sensor properly you should disconnect the plug from the sensor connect the positive lead of a volt meter to the grey wire and the negative lead to the black wire, with the ignition on engine not running, the voltage should be 5 volts. Then plug the plug back into the sensor and backprobe the green wire(middle wire) with the positive lead of the meter and the negative to a good ground. With the ignition on the volts should be 4.0 to 5.0. Then start the engine and allow to idle and the voltage should drop to about 0.5 to 2.0. If results are incorrect replace MAP sensor. To check the TPS for voltage disconnect the plug from the sensor and connect the positive lead of a volt meter to the grey wire terminal and the negative lead to the black wire terminal, turn the egnition on, engine not running and the volts should be 5.0. If voltage is incorrect check the wiring from the TPS to the ECM(electronic control module)To check the TPS Operation reconnect the plug to the TPS, backprobe the blue wire with the positive lead and the negative to a good ground point, turn egnition on, engine not running, throttle fully closed the volts should read approximately 0.6 volts, then gradually open the throttle and the volts should increase smoothly to approximately 4.5 volts with the throttle wide open, if results don't match up replace the TPS. But I think before you do all that u should check the timing with a timing light, let meknow how it goes good luck!
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Tuesday, November 14th, 2006 AT 1:40 AM

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