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Well a code came up finally for a Map sensor which says high output. Does this mean it is bad ? I thought low output is a bad sensor ?:dunno:
 

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Discussion Starter #4
No never replaced the map sensor. What would regulate the voltage to be too high or low ?
 

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No never replaced the map sensor. What would regulate the voltage to be too high or low ?
I was thinking that message ment the sensor was sending too high a voltage to the CPU. Well at least to high a signal. I would assume voltage.
 

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Discussion Starter #6
Ok well where do I go with this. I replaced the PCM last year, so I doubt that is it. I am more af a carb guy so where should I look to see whats causing it a high voltage ?
 

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Ok well where do I go with this. I replaced the PCM last year, so I doubt that is it. I am more af a carb guy so where should I look to see whats causing it a high voltage ?
the map sensor its self can go bad and read wrong but normally they dont so i would geuss that you have a vac leak going to it so its not reading correctly and sending the ecu a mix message. i hate speed density efi systems. its funny how gm used maf and switched to sd but ford had sd and switched to maf in the late 80's cus it was more accurate and actually measures air flowing into the motor.... not using a vacum measurement to geuss what the motors demand for air and fuel is like sd which uses the map sensor.
having said all that i would try a new sensor and look for a leak if it doesnt help
 

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Discussion Starter #8
You said they normally dont go bad but recommend a new sensor ? The sensor is a 100 bucks. I will check out the vac lines first.
 

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86 Rokee check out Four Eyed Forums.com. I have a 83 T-top. Its weird a lot of Cherokee owners have a Mustang !
 

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I ordered one. I'll let you know if it makes my miss go away.
 

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Haha. All those cherokee owners who own a mustang made a good choice when they bought the jeep. Now where did their brains go when they bought the ford?
 

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Haha. All those cherokee owners who own a mustang made a good choice when they bought the jeep. Now where did their brains go when they bought the ford?
I don't know about the cars, but Ford makes a damn good truck. At least the 89 and 94 F150's I had were great trucks. Better than the 2 Chevys that I owned.
 

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Well here you go. On an XJ map sensor, and most others for that matter, a high MAP voltage output amounts to low vacuum, and low voltage output amounts to high vacuum. If your vacuum line from the manifold is not cracked and you have a good vacuum to the MAP sensor, then you have an electrical issue. Check for a ~5.0 volt supply to the sensor and make sure it has a good ground at that same connector. I can't tell you wire colors because I don't know your XJ's year...If you have good 5.0 reference, plug the harness back in and back probe the remaining wire...that is your signal voltage...with it running and good vacuum, you should have about 1.5 or so signal volts. If you do, problem in intermittant. If you still have high voltage the sensor IS bad, i.e. shorted internally. I could go on about how to diagnose it, but that should get you in the right direction. Good luck...
 

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Discussion Starter #16
Popped one out of the boneyard and threw it on. First i started it and it died, second time almost died and sprung to idle. Works great now and it seems like it grew more balls as well.
 

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Popped one out of the boneyard and threw it on. First i started it and it died, second time almost died and sprung to idle. Works great now and it seems like it grew more balls as well.
Damn! I've had more than one person tell me "those rarely go bad". If my new one fixes my MPG problem as well as the miss, I'm hunting them down and getting several hundered dollars of gas money back from them.

So you didn't disconnect the battery for 30 minutes, to reset the computer?

Glad to hear it's fixed.

Are you going to replace that one with a new one, or just wait until it starts missing again and then replace it?
 

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Discussion Starter #18
No I didnt disconnect the battery and eventually might buy a new one but I am not in a hurry. Actually I will just hit the boneyard again.
 

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86 Rokee check out Four Eyed Forums.com. I have a 83 T-top. Its weird a lot of Cherokee owners have a Mustang !
im already a memeber,lol, small world. jeepsand stangs, u cant go wrong!
im on there as:

86GT5spdEVERETT
whats your sn on there?
not to steal the thread
 

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Well here you go. On an XJ map sensor, and most others for that matter, a high MAP voltage output amounts to low vacuum, and low voltage output amounts to high vacuum. If your vacuum line from the manifold is not cracked and you have a good vacuum to the MAP sensor, then you have an electrical issue. Check for a ~5.0 volt supply to the sensor and make sure it has a good ground at that same connector. I can't tell you wire colors because I don't know your XJ's year...If you have good 5.0 reference, plug the harness back in and back probe the remaining wire...that is your signal voltage...with it running and good vacuum, you should have about 1.5 or so signal volts. If you do, problem in intermittant. If you still have high voltage the sensor IS bad, i.e. shorted internally. I could go on about how to diagnose it, but that should get you in the right direction. Good luck...
good info:thumbsup:
 
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