No Acceleration

1998 CHEVROLET LUMINA
120,000 MILES
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HOOTY
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The car still has good take-off. I can accelerate normally up to 25mph but then it stops accelerating and is very laboring to get up to 40mph and higher. A relative of our told us of a similar issue and they cleaned the Mass Air Flow (MAF) sensor and everything was fine. I disconnected my MAF and the car runs great! I replaced the MAF but the car returns to the same problem as soon as I connect the sensor back up. What's the deal?
Jun 4, 2011 at 1:19 PM
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JDL
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Any applicable trouble codes? What is litre size of engine? Check ref voltage and ground for the maf sensor. Is the maf sensor new?
Jun 4, 2011 at 3:56 PM
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HOOTY
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No trouble codes have appeared except when I disconnected the MAF sensor. I have a 3.1L The MAF sensor is new but did not make a difference in the performance. I'll check the voltages and reply back tomorrow.
Jun 5, 2011 at 1:43 AM
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JDL
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At the sensor, pink is voltage, yellow is signal from maf to computer, black wire with white tracer is ground.
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Jun 5, 2011 at 4:46 PM
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HOOTY
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I checked the voltage and it reads 12.2V. We noticed something else when driving. It makes high-pitched sound and occasionally sounds like a water sprinkler when the accelerator is depressed about half way. The sound disappears when I let off the accelerator or floor it. I also noticed a significant power increase when the sound disappeared. From the inside, it sounds like the source is directly behind the steering wheel. I thought it may be a vacuum leak but I was not able to locate it. I pulled off the brake assist hose and plugged it but we were able to get the sound to come back. Could this be related?
Jun 5, 2011 at 9:16 PM
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JDL
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I don't know about the sound? I keep going back to maf sensor. Use a test lite between voltage and ground at the maf connector.

Clean the throttle-body, check tps. Make sure the maf wiring isn't routed over plug wires.
Jun 6, 2011 at 2:26 PM