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Doug
Doug, ASE Certified Technician
Category: Car
Satisfied Customers: 8610
Experience:  16 years automotive and OTR repair including specialized training from Toyota and Mitsubishi
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I have a PO172&PO175 code & both banks long fuel trim are -12.

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I have a PO172&PO175 code & both banks long fuel trim are -12.50 what do think is wrong
Hi,

How often does the problem occur? Is there any specific thing you can identify that is common to each occurrence?
Customer: replied 4 years ago.
it says reduced power when check engine light comes on i checked fuel pressure its not too high its 25psi
Hi,

This is a very low pressure reading and should be cause for alarm. Normal operating pressure is 42 PSI.

Having this low pressure issue will prevent the fuel from atomizing properly and give you the trim range faults, so this must be pursued first.

Try clamping off the fuel return line and checking pressure again. If the pressure goes up to 40-50 PSI, you need a new fuel pressure regulator. If the fuel pressure remains low (25-30 PSI etc), then you will need a new fuel pump.
Customer: replied 4 years ago.

i rechecked fuel pressure with a new guage i have 40 PSI now the MAF i tried was after market from worldpac & it looked like it was used do you think i should try another one

Was the behavior identical between the original MAF and the Worldpac provided MAF?
Customer: replied 4 years ago.
i swaped them back a couple of times and every time i put the one from worldpac on the car will not accelerate or idle smooth and with the old one it runs fine for a few weeks after i clear the codes
Thanks.

If the Worldpac one is giving you problems that the original was not, and with the original it runs for a while then acts up again, I would first and foremost send the new one back to Worldpac and either get another or get one from Jag to eliminate that variable.
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