87 Bronco II, 2.9 V6 EFI, all stock with the 4-spd auto. recently replaced fuel pump relay.



Garage minds, does this sound like something that can be easily diagnosed:

thing starts, idles, warms up fine. Runs with no hesitation or missing at minimal/part throttle, and can be driven up to 55mph under part throttle (less than half throttle).

It hesitates and misses under these conditions:
- accelerating from a stop greater than half throttle
- attempting to accelerate from 55ish up (again, where a greater throttle position is needed)
- any hard acceleration where dropping a gear is necesssary


basically it seems that the trouble is completely dependent on throttle position/fuel need.



Could the problem be (but not limited to):
- clogged fuel filters
- TPS ( i cant remember if it has one)
- fuel pump??




(the thing will eventually be taken to someone who knows what the fuck is going on, but right now i'm trying to be joe-mechanic and try my hand at it)

10/21/2007 10:43:17 PM

see if you have any codes: http://www.thorssell.net/hbook/eectest.html

It might tell you something, it might not.

10/22/2007 12:00:16 AM

i'd start with the fuel system, check your pressure first under load

10/22/2007 8:20:14 AM

There are two fuel pumps. A low pressure one in the tank and a high pressure one under the driver's door...More than likely one of them is dead.

10/22/2007 10:26:42 AM

fuel pump relay was faulty.

installed another one and it runs correctly now.


fyi

10/25/2007 10:56:58 PM

Quote :

"recently replaced fuel pump relay."

Made me assume that the relay was good. Glad it worked out for you. Which pump was losing power?

10/26/2007 11:00:31 AM

yeahhh, I was hoping a new part from the great Advance Auto would function correctly. As for which pump, couldnt tell you. I never got to touch the vehicle after the initial problem diagnosis, because girlfriend's family was working on it after I had to return to school. Her uncle decided to check out the relay one more time before they got serious about it, and it worked out for them.

10/26/2007 11:15:38 AM