MAP Sensor

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Jun 14, 2002 | 07:44 PM

panamint

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Joined: Jun 2002

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MAP Sensor

I have a 92 F-150 with a 5.0 E4OD 155000 miles, EEC ignition and I live in the mountains at 7000 ft. Everytime I travel to lower elevations the truck runs bad( loss of power sputtering when taking off from a stop or when giving it gas). I was wonding if this could be the MAP sensor, there are no codes stored in the computer. Is there a way to test it or just spend the $85.00 and try a new one. Also do the code checkers that cost around $45.00 and just blink and you count the codes worth the money?

Jun 15, 2002 | 05:37 AM

cajunbronco

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Joined: Feb 2002

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MAP Sensor

I would'nt waste my money on the cheap code reader.You can do the same thing by jumping the diagnostic test connector leads and it will flash out codes on the check engine light.Do a search on the net for ford trouble or eec codes.There are several sites that how you how to do it.As for the map you can test it with a voltmeter and a vacuum pump.A haynes manual will describe the procedure.For a quick check,if the engine is running unplug the map it should kill the engine.

Billy

Jun 25, 2002 | 12:04 PM

steve4413

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Joined: Apr 2002

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From: Concord USA

MAP Sensor

Next time you have this problem try turning the key off and restarting. This resets the map sensor to the altitude that you are at.

Jun 26, 2002 | 01:17 PM

winfordr

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Joined: Jan 2001

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From: Rural Florida Panhandle

MAP Sensor

I agree with cajunbronco. The MAP sensor only works at startup. It produces a varying FREQUENCY signal depending on atmospheric pressure. I would use a set of sensitive headphones and vacuum source to test it.

Winford

Jun 27, 2002 | 09:18 AM

Lightning2Fast

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Joined: Feb 2002

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From: ct

MAP Sensor

the map sensor does NOT only work at startup. it has a function whenever the engine is running. it is the major load sensor. this is why it has a vacuum line connected to it. as load increases vacuum drops. this the map then sends a signal in hz to the pcm. the pcm then delivers the correct amount fuel by manipulating the injector pulse. this is a nutshell explanation of course. the pcm also monitors t/p and 02 readings to determine the engines actual load. this is why when you unplug the map at idle the engine stalls. the pcm thinks there is no engine vacuum and dump large amounts of fuel into the engine. it just gets too rich to run and it stalls. also this is why speed density doesnt get along too well with aftermarket cams. the vacuum at idle is not high enough. the pcm creates a rich condition and now you can barely get the truck to idle.

Jun 27, 2002 | 12:16 PM

winfordr

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Joined: Jan 2001

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From: Rural Florida Panhandle

MAP Sensor

I stand corrected. I confused the MAP sensor with the BP sensor, which is basically the same device, but does not have manifold vacuum connected. It is the one which senses barometric pressure, and is used on mass-air systems.

Sorry for the mixup.

Winford