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bad map?

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Old Apr 2, 2008 | 11:31 AM
  #1  
IceboxFX's Avatar
IceboxFX
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bad map?

I unplugged the MAP sensor and took the truck for a drive. The truck felt exactly the same as it always did, the only difference was the CEL came on. If the MAP sensor is bad would/should the CEL come on? If not, could this be mean the sensor is bad because it is running the same?


Thanks guys,
Brian
 
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Old Apr 2, 2008 | 11:34 AM
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If its running the same then the MAP is fine. If it runs better than the MAP is bad.
 
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Old Apr 2, 2008 | 11:37 AM
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ok good deal, thank you
 
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Old Apr 2, 2008 | 11:44 AM
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Tim, correct me if i'm wrong, but isn't another test (just to double check map) disconnect the line and plug it. Then drive around and it should be ******* a bit. If it's *******, map is good. Also, you could pull the line and put your finger over one end and blow a bit of air from a compressor in the other side and see if it can hold come pressure, or just replace it.

-Robb
 
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Old Apr 2, 2008 | 11:46 AM
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yes you could pull the hose off it. Did that once on accident after doing a GP on that side. had the acceleration of an IDI. I was really nervous until I remembered that I didn't hook that back up!
 
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Old Apr 2, 2008 | 12:05 PM
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Originally Posted by tjbeggs
yes you could pull the hose off it. Did that once on accident after doing a GP on that side. had the acceleration of an IDI. I was really nervous until I remembered that I didn't hook that back up!

Hate when that happens!!!

Bill
 
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Old Apr 2, 2008 | 12:50 PM
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Originally Posted by IceboxFX
I unplugged the MAP sensor and took the truck for a drive. The truck felt exactly the same as it always did, the only difference was the CEL came on. If the MAP sensor is bad would/should the CEL come on? If not, could this be mean the sensor is bad because it is running the same?


Thanks guys,
Brian
If the map sensor is completly bad (not putting out any signal) the truck will cel. On power up the map puts out a frequency between 100 Hz and 109 Hz, depending on your altitude. Mine puts out 108.6 Hz at 2000 feet. As boost increases the frequency of the sensor increases to some upper limit of around 167 hz, a lot of boost. If for whatever reason the sensor does not increase in frequency, such as a clogged hose in my case, as boost increases the PCM does not know and won't increase fuel flow, thus poor boost assist.

At least that is how I understand the theory.
 
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Old Apr 2, 2008 | 04:01 PM
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forgive me for my ignorance as long as i been on this site- but where is the map sensor?
 
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Old Apr 2, 2008 | 04:04 PM
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read this link:
https://www.ford-trucks.com/forums/7...issue-yea.html
 
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Old Apr 2, 2008 | 04:25 PM
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ok, just tried it, and no diffference in performance when i unplugged the electrical connector.
 
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Old Apr 2, 2008 | 07:11 PM
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TJ wrote this above
Originally Posted by tjbeggs
If its running the same then the MAP is fine. If it runs better than the MAP is bad.
 
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