Map Sensor Question (Very Interesting)
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Map Sensor Question (Very Interesting)
First of all, thank you everyone for your past help. New problem. `89 Club Wagon 302 stalls, hesitates and loss of power. Had it completely tuned up last summer(New Napa Premium Wires Cap & Rotor, Bosch Platinum Plugs). New fuel filter and K&N Air Filter also. I was stumped, So on a whim I unplugged the MAP Sensor and to my total amazement found that it runs GREAT!!!, except for a little black smoke out the tail pipe when idling and a little pinging under WOT. Great power, throttle response and overall performance, shifts excellent. MPG doesn`t seem to be affected and remains at 14-15 miles per gallon. Also, there is no fast idle when cold, but I can start it, put in in gear and drive off like the engine was fully warmed up! I`ve driven it about 150 miles since I disconnected the MAP.My question is this, what does the MAP Sensor really do and what would explain this dramatic improvement in drivabilty and performance with the Map disconnected ?????? Please don`t think that I`m joking around here, I am serious!
Posting Guru
Joined: Dec 2003
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From: SW Arizona
Manifold Air Pressure (MAP) Sensor
Its job is to keep the computerized engine control system informed about engine load so the fuel mixture, spark timing and other emmission fuctions can be adjusted to suite changing operating conditions. It's an essential job taht requires accurate calibration and trouble free operation for good engine performance and driveability.
Its job is to keep the computerized engine control system informed about engine load so the fuel mixture, spark timing and other emmission fuctions can be adjusted to suite changing operating conditions. It's an essential job taht requires accurate calibration and trouble free operation for good engine performance and driveability.
Had to go look that one up, myself and it does give an overview of Ford's MAP.
If it fails or not working right, usually your vehicle will have starting/stalling problems, bad mpg, and poor performance. In your case, outside of not having a fast idle at cold, the pinging and a little black smoke, you can drive it just fine. Your specific results from unhooking the MAP have to do with not having a sensor dealing with air/gas mixture with your EFI. For example, the black smoke means you are running with too rich a gas mixture.
My husband would have something to say about "rocket scientists" and vehicle computers. A couple of times, he felt like taking a hammer to his 83 van's sensor box.
My 79 Chrysler Cordoba had an earlier version of this with it's Lean Burn System computer on the side of the airbreather. The carburator had a sensor wire connected to it to help regulate fuel. Some of these did go out or became faulty. Fortunately, you could replace the system with a regular points/distributer and reset/adjust the carb so it would not "lope" while idling or stall because not having the sensor anymore.
I would count my blessings.
Last edited by VikingBabe; Sep 6, 2005 at 06:45 AM.
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Hmm... I'm surprised you didn't get a CEL... A few years ago the MAP sensor went on my '90 5.0 EFI and it threw a code and lit the CEL. Ran like crap and idle was all over the place.
When you unplugged the sensor, the computer defaults to a set of "generic" values in order to operate - typically erring on the rich sde. I'd hazard a guess there is little chance of the engine passing an emmisions inspection right now and it may be damaging to the o2 sensor and cat.
When you unplugged the sensor, the computer defaults to a set of "generic" values in order to operate - typically erring on the rich sde. I'd hazard a guess there is little chance of the engine passing an emmisions inspection right now and it may be damaging to the o2 sensor and cat.
More Turbo
Joined: Jun 2004
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From: Sweden
You might have another problem leaning out the mixture so with the sensor unplugged and it defaulting to a mixture which should be rich it works out to something better. But I'd certainly want to get the original problem fixed and the MAP back in place!
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