RWD - MAP Sensor test?

Volvo RWD 700 Forum

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MAP Sensor test? 700 1991

Just signed up to the forum. I have been gathering information for a while off of here, and others, and thought I may join and ask my questions. I was gifted a 1991 740GL with the Regina system last year, and have been doing all that I can with my limited time and resources to get it running correctly. This car had been sitting in the parking lot at work for at least 6 years before I got it. First thing I needed to do was replace the fuel pump which had gone faulty. The car ran pretty well, but it started like an old carbureted engine with a bad choke. I would have to put my foot on the pedal just a bit for it to start, and I would have to keep it in that position until it warmed up a bit. After that it would idle without dying, but the idle was very rough. Acceleration was a bit sluggish, but it drove well. I read that the rough idle could be caused by a dirty throttle body, so I removed that and cleaned it thoroughly. No luck in diminishing the rough idle. I also read that the the idle control valve could cause this. While running the diagnostics check from pin 2 in the OBD I was able to visually see the valve opening, so I crossed that off of the list. In the mean time, the car started to lose power and stall. I found that the crank position sensor had gone bad, and replaced that. At this point the car was back to a hard start, and having to keep my foot on the gas until warm up. I bench tested the intake air temp sensor, and found that it is working. Just for grins I disconnected the vacuum line to the MAP and found that the car would idle without stalling, and would start m,ore quickly. While I had it running I put my finger over the vacuum port, and the car car still idled without stalling. It does a lot of fluctuation in RPMs with the MAP disconnected, but I expected that. I replaces the vacuum hose with a length of fish tank tubing, and that didn't help. Given that the ID is bigger than the stock line I thought that I would pay it little mind.

Now that my long winded explanation is over, is there an easy way to bench test the MAP sensor? Does it sound like a sensor issue, or was it just a fluke that taking the vacuum line off helped? I got this car for my daughter, she will be getting her license in a few months, so I need to get it running correctly. Any guidance will be appreciated.


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New MAP Sensor test? [700][1991]
posted by  motorD  on Wed Jan 17 10:23 CST 2018 >

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