Questions and Answers

Chevy S-10 Blazer Weird MAP Sensor Q. Greetings from Costa Rica, 1986 Chevy S-10 Blazer 2.8 liter 4x4 automatic transmission with a 1987 wire harness and ECU. Here is the problem; car is running very rich. Went to one of the tech boys down here and this is what we found. All sensors are within limits.

But listen to this, when we unplugged the MAP sensor vacuum hose from the MAP sensor, all readings regarding emissions when to the bottom of the chart 0.00 CO, 0.15 HC. If we unplugged the wires the reading went up again. So without the vacuum hose connected, and with the wire harness connected, the car will pass inspection.

The MAP sensor seems to be working. We changed it with another and the same thing happened, but that's it. Nobody has any idea what's up, so I guess my question is: What's up?

Thanks,
Kim

A. The harness may have wires for different sensors for this year car. There may be a barometric sensor on one and not the other. You will need schematics for both models to see what the difference is.