1989 Chevy Silverado Running Problem

Tiny
BILLYL
  • MEMBER
  • 1989 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 11,000 MILES
Truck has always ran fine. One morining got in it would not start. Everything checked out, I unplugged the map sensor and the truck started and ran ok. But when You put into drive it would stop running. Got a new Map Sensor, plugged it in and it would not start. Then I unplugged the map sensor and it would start up and run smooth, but would go dead when I put it into drive. I have replace everything and must be missing something. So help me out. Please reach me at billylothridge@yahoo. Com
Monday, July 5th, 2010 AT 6:29 PM

3 Replies

Tiny
INTERNETMECHANIC
  • MECHANIC
  • 700 POSTS
Were there any applicable trouble codes before you replaced anything? Did you check sensor wiring circuits? Do you have good vacuum at idle? If you unplug the map sensor, the computer will use a default value and use the signal from the tps to help with fuel. The map and tps share ref voltage circuit.
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Thursday, September 3rd, 2020 AT 9:58 AM
Tiny
BILLYL
  • MEMBER
  • 3 POSTS
Thank You for getting back to me. I read the code and it was 33 which is the map sensor on this truck. Now I have replaced all of the vacuum hoses and also have a new TPS and a new Idle Air control and put a new gasket under the throttle body. Have not checked the sensor wiring circuits, don't really know the right way to do this, give me the step by step way of doing this, I really don't know what I have overlooked, it may be simple, I have never ran into anything like this before. Got any other ideas
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Thursday, September 3rd, 2020 AT 9:58 AM
Tiny
INTERNETMECHANIC
  • MECHANIC
  • 700 POSTS


https://www.2carpros.com/forum/automotive_pictures/512072_89_chevy_map_sensor_1.jpg



In the diagram, you can see the circuit for ref voltage. Take the connector loose from map sensor, turn the key on, no need to start. Use a digital multimeter check for around 5 volts. You can check ground also, I use a simple L.E.D., like you get from radioshack. You'll probable need to use a resistor with the led, some leds can't handle more than a volt and 1/2. One end goes to battery voltage, the other end goes to ground terminal at the map connector, connector unpluged, if the ground is good, the lite comes on.

With the engine running, do you have vacuum at the map sensor, feel.
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Thursday, September 3rd, 2020 AT 9:58 AM

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