Working on a friend's 91 GT. Had to fix a mess with the vacuum lines. They were routed all wrong. Then I noticed a vacuum line was run from the intake to the MAP/BAP sensor. On a mass air car, there is no need for a vacuum line there as it reads atmospheric pressure. I disconnected it and plugged the intake. The reason for going through the vacuum system is the car is running extremely rich. I fired it up and it ran like complete poop. Checked vacuum lines again and didn't see an issue. Then, I questioned why it ran so much better with that vacuum line hooked up to the BAP sensor. So it hit me, I think someone installed a speed density ECM in this car and they tried to just give the BAP sensor some vacuum. Could this be why it's running so rich? Is the wiring harness different other than having the connections for the MAF? Any help would be great. I have a friend with a mass air ECM, so I'm gonna try it when I can.
Different wiring harnesses. So a SD ecu on a MAF car is not good.
I was doing a little research today and found that the pinout is different. Looks like that may explain some of the codes I'm getting. Seems like all they did was install a SD ECM and run a vacuum line to the MAP sensor. Smh!
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