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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23821
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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Help!!! I have a 05 Ford F350 Crew Cab 4x4 DRW 6.0 It has

Customer Question

I have a 05 Ford F350 Crew Cab 4x4 DRW 6.0
It has been bullet proofed. Changed rear end gears from 450 to 373, trying to help mpg. 12 to 13 hwy.
10.5 to 11 towing around 8,000 lbs. All this with SCT TUNER set on street tune. Had computer flashed said it would help mpg, something about cold start issues. The last shop said I didn’t have a Mass Air Flow Sensor. You could see where the wire harness looked like it had been cut off. It does have an Air Temperature Sensor on it. So they put a 6 wire MAFS sensor on. I did pick up 2 mpg without the tuner, only riding no towing.
All was well until I pulled my first load, still in stock mode, no tuner. The boost pressure starting going up to 30+ on a hill. At steady throttle the boost will go from 30+ to 18 back and forth, you can hear the engine sound change when it does this. They changed the Exhaust Back Pressure Sensor; solenoid in turbo didn’t help anything. Finally with the Exhaust Back Pressure Sensor UN plugged the boost went back to normal. They now say the turbo is at fault. I had it replaced less than 6 months ago.
My question is if the turbo is bad, why UN plugging the EBP sensor fixed the boost problem. I spoke with one of the programmers at SCT Tuners; his thoughts were the computer isn’t set up right. Keep in mind the TECHS are ford certified, using ford equipment. I don’t know what to do next. Iam located outside of Winston Salem NC.
Submitted: 1 year ago.
Category: Ford
Expert:  Ray M. replied 1 year ago.

When you are pulling but not hard and the engine changes sound is there a sound like air being blown off under the hood?

Customer: replied 1 year ago.
No only sometimes when I let off throttle quick.
The only time the engine changes sound is under a steady pull, that's when the boost goes up and down.
Expert:  Ray M. replied 1 year ago.

When the engine sound changes is there a loss of power?

Customer: replied 1 year ago.
No not really, maybe a small amount . It will just keep boosting up and down with steady throttle
Expert:  Ray M. replied 1 year ago.

you said you installed a MAF sensor, the 2005 did not use a MAF sensor there was only a intake air temp sensor mounted where it should have been. It sounds like the turbo vanes are sticking and causing boost pressure to backfeed, the reason unplugging the EBP sensor helps is the PCM uses it to adjust the turbo vanes and when it sees no signal it uses a default setting.

Customer: replied 1 year ago.
The guys said it was suppose to have one. It did help mpg. 2 more miles. It does have an air temp sensor on the air filter box. I was told by another tech that with an air temp sensor they should have put a 4 wire maf on instead of 6 wire maf on the air filter box. I did not have this problem until the MAF was installed. The turbo is less than 6 months old.
Customer: replied 1 year ago.
They said they could not check turbo because of the EGR DELETE.
Customer: replied 1 year ago.
A local shop hooked up his scanner to turbo and was able to open and close what ever is in the turbo.
Customer: replied 1 year ago.
They a an 05 at there shop that had a MAF on it , that was what started my quest, on my first visit when they replaced my fuel sending unit. They had to call the Ford Tech hotline to be sure my truck came with one on it . I am the second owner.
Customer: replied 1 year ago.
They also cut the wires on the EBP when they put the MAF on. They did hook them back together, wires were not same color could one be out of place?
Customer: replied 1 year ago.
Are you still there?
Expert:  Ray M. replied 1 year ago.

Yes if one of the wires are out of place it could be shorting out or feeding 12 volts the PCM on the VREF signal return.

Customer: replied 1 year ago.
it could be a combination of both unplugging the EBP helps and the wires are in wrong place. How would I find out how they should be wired up?
Customer: replied 1 year ago.
Does the VREF signal go to the turbo
Expert:  Ray M. replied 1 year ago.

No, the VREF signal comes out of and returns to the PCM, It could be screwing up the control for the turbo though. You wouldhave to get a connector pinout diagram from your local Ford dealer.