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Pete, Automotive Mechanic
Category: Transmissions
Satisfied Customers: 28763
Experience:  GM and Mercedes vehicle technician.17 years experience.
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2004 Taurus no power. Starts and run good. When it is put in

Customer Question

2004 Taurus no power. Starts and run good. When it is put in gear it will not go over 20 miles an hour. Changed fuel pump and have good pressure. Good vacuum, pulled upper oxygen senser to check for clogged cat and it did not help. changed fuel pressure regulator. no misfires and only engine codes are for high temp fuel rail.
Submitted: 1 year ago.
Category: Transmissions
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to help with this today.I apologize for any delay.

Is the transmission upshifting at all with this issue or does it feel like it is stuck in low gear (1st or 2nd gear)?

Let me know so we can continue,thanks Pete.

Customer: replied 1 year ago.
Seems to be shifting OK, RPM will not go over about 2000 loaded, engine boggs, same thing if sits still with brake on.
Expert:  Pete replied 1 year ago.

O.k.,locate the mass air flow sensor located in the air inlet tubing leading from the engine air filter to the throttle body.This sensor can sometimes become dirty needing cleaned.You can purchase mass air flow sensor cleaner from a local parts store to clean off this sensor.I have seen this sensor cause this issue here needing cleaned or if it is shorting out internally it would need replaced.

One way you can tell this sensor is the cause here is if you unplug it with the key off then start the engine and run it briefly see if it has the same loss of power.If it runs much better then the sensor needs cleaned or replaced.

I would still do a complete exhaust back pressure test.Even though you removed the oxygen sensor this doesn't give the exhaust enough flow to exit from if restricted.I would see if you can rent a back pressure tester to thread into the oxygen sensor port before the catalytic converter and run the engine at idle all the way up to wide open throttle briefly to see if the back pressure exceeds 1.5 psi.If it does exceed 1.5 psi then the catalytic converter most likely needs replaced.

These two issues here will cause this fault.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.Thanks Pete.