Help 7.3 missing, no codes, did buzz and contribution tests - Ford Powerstroke Diesel Forum
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  #1  
Old 08-27-2010, 06:25 AM
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Help 7.3 missing, no codes, did buzz and contribution tests

My truck just decided to run horribly, when I shut it off.
Started missing, seemed like one cylinder but could have been 2, not real sure.
No power, 300 to 400 degrees higher EGT's, didn't seem to smoke any more than usual.
I took it in to Ford Dealer to get a scanner on it. They did a code check and came up with nothing. Said the truck was missing. When they did the Buzz test every injector was fine. When they did the contribution test, they said that #3 and #8 were only at 80%, but still no codes in computer.
No SES light either, at anytime.

Does anyone have any ideas?
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Old 08-31-2010, 05:20 AM
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does anyone have any ideas? All ideas would be appreciated.
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Old 08-31-2010, 01:28 PM
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Shot in the dark, but this worked for me with VERY similar symptoms. I unplugged my MAT sensor and everything cleared up! I don't know if the MAT can be cleaned but I just ordered a new one for $10 on ebay.

Until I receive it, I just have the MAT unplugged, so the computer is defaulting to a standard failsafe setting. Its worth at least giving it a try. As soon as I unplugged the sensor, the truck ran great and all my white smoke and stumbling went away.

Give it a try and let us know if it helped at all?
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Old 09-01-2010, 06:06 PM
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MY truck is doing the same thing. I havent tested anything yet since it has just started acting up. I am not getting any ses light. and for some reason my fuel gauge jumped up to say it was full even thou I got about $20 in it. I wonder if its related. it starts up fine and then just runs rough from idle all the way up.
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Old 09-01-2010, 10:44 PM
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Did you try pulling the MAT sensor for fun? It takes 30 seconds and it's worth a try. It's one of the sensors that contributes to fuel delivery and if/when the sensor goes bad it contributes to white smoke and extreme rough idling.

Try it and let us know if it helps.
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Old 09-08-2010, 05:31 AM
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OK having a bad brain day.
What is the MAT sensor and were is it?
Thanks for all the help.
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Old 09-08-2010, 06:02 AM
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Ah yes, it is amazing what a cup of coffee can do for me.
MAT sensor= IAT Sensor- Intake Air Temp sensor.
This can be tested with a Ohm meter and a Hair Dryer. Take a ohm reading cold, then take one warm and then hot, using the hair dryer. Your repair manual should have acceptable reading ohm amounts in it.

Thanks for the heads up, didn't think about that causing the problem, since it helps with exhaust gas recirculation amounts.
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Old 09-08-2010, 07:36 AM
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Tried that, AIT sensor, but didn't change anything.
So I tested the sensor with a ohm meter, sensor is good.

Any other ideas?
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Old 09-08-2010, 09:38 AM
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I didnt bother to test it with an OHM meter, I just unplugged it and ran the motor. My smoke dissapeared instantly. When I plugged it back in, smoke was back. Sorry I couldnt be more help. Is this the sensor you tried? The MAT is different from the AIT
Here is the MAT:
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  #10  
Old 09-08-2010, 10:51 AM
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No that wasn't the sensor that I checked first.
I did check that one, by unplugging it, it still didn't make any difference.
Thank you for all your help though.
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