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I have a 99 F250 5.4 Super Duty. OBD is reading -40 degrees.

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Hi Chris. I have...
Hi Chris. I have a 99 F250 5.4 Super Duty. OBD is reading -40 degrees. Engine hesitates while driving. No misfires.
Submitted: 2 years ago.Category: Ford
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Answered in 4 minutes by:
10/6/2015
Ford Mechanic: Chris (aka- Moose), Technician replied 2 years ago
Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 49,129
Experience: 16 years experience
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Has anyone installed one of those resistors on the vehicle to confuse the IAT reading to the PCM?

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Customer reply replied 2 years ago
Not that I know of... Third owner of the truck. Thought it was initially fuel injectors or coils.. Or fuel pump.. But the mechanic I've been taking it to insists on it having something to do with the computer system
Customer reply replied 2 years ago
Whether it's a faulty or a corroded wire.. Confirmed the reading today that it was reading - 40. He said once he plugged a sensor back in it should read 1000 degrees????
Customer reply replied 2 years ago
Other opinions included a bad catalytic converter.
Ford Mechanic: Chris (aka- Moose), Technician replied 2 years ago

Are you getting any trouble codes? The cold IAT reading can effect the air fuel ratio and cause running issues. So we need to address the known issues prior to testing other things. Have you done any testing on the IAT in the MAF sensor or its wiring?

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Customer reply replied 2 years ago
I do plan on rating you at a later time. I do appreciate your help! To my knowledgethe truck wasn't throwing any other codes. And there has been no testing to the IAT.
Customer reply replied 2 years ago
Not yet anyways.. The truck does seem to be "dumping" a lot of fuel while driving.
Ford Mechanic: Chris (aka- Moose), Technician replied 2 years ago

Lets do those IAT tests first. See the steps below. I told you wrong on the IAT and MAF integrated, that si not until the next year model. The IAT is a stand alone sensor in the air intake tube to the throttle body.

Unplug the IAT connector and jump the Gray (GY) wire to the Gray/Red (GY/RD) wire and watch the IAT voltage reading on the scanner. If it goes to under 0.1 volts, replace the IAT. If the reading does not change, verify the GY and GY/RD wires are good from the connector back to the Powertrain Control Module (PCM). If all is OK, replace PCM.

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Customer reply replied 2 years ago
Thank you Moose. Am I able to ask you questions tomorrow as well?
Customer reply replied 2 years ago
I should mention over the past few weeks there have been moments where the truck drove great but never lasted more than two days. I commute to work about 50 miles total every day.
Ford Mechanic: Chris (aka- Moose), Technician replied 2 years ago

We have 7 days to try and get posts rated. After its rated the post is open forever.

Once we get the IAT reading right we can look into other residual issues remaining.

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Ford Mechanic: Chris (aka- Moose), Technician replied 2 years ago

I am sorry you were not pleased with my help. I am still available if you would like to try again. I want you pleased with me.

Chris

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