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fordtechsuzukitech25
fordtechsuzukitech25, Ford Technician
Category: Ford
Satisfied Customers: 98
Experience:  master ase certified,senior master ford certified
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F-250 Pickup: 1997 Ford F-250 7.5l 460ci engine with 222,000

Customer Question

1997 Ford F-250 7.5l 460ci engine with 222,000 miles. Had a stumbling problem for a few years when not warmed up before driving. Used to drive 35 highway miles to work and it would do fine if warmed up before driving, except at the offramp after driving the 35 miles it would have a rough idle and would really stumble hard when leaving the stop at the bottom of the offramp. The problem was manageable until it lost all power heading up an onramp (foot on the floor and engine slowly ramped down and wouldn't start at all). Had both fuel pumps replaced and the mechanic cleaned what he said was a dirty Mass Air Flow sensor. He said the fuel pressure was too low. Truck has run fine for about a year and now it's doing the same stumbling again, except it's more extreme when climbing steep mountains. It bucks, shifts out early, shifts out late, and at times seems to lose power for a second or two. I disconnected the batter and replaced the MAF. It ran quite a bit better with just a bit of hesitation, but after about an hour total of driving, the bucking returned. It also seems at times there's what I call an internal backfire: not a gunshot out the tailpipe, but a loud knock that seems to come from the engine compartment, but that doesn't happen unless it's doing the severe bucking. I think my next step is to check for some serious leaks between the MAF and the throttle body, but I"m worried that the computer is learning to be bad and it could be bad signals or a bad computer. I've had good luck searching problems/solutions out on this site and I thought for sure it was a bad MAF because the behavior descriptions seem so close to my situation. Any ideas?
Submitted: 1 year ago.
Category: Ford
Expert:  fordtechsuzukitech25 replied 1 year ago.
I would start at the beginning,check fuel pressure, throttle position sensor, and oxygen sensors. are there any codes?
Customer: replied 1 year ago.
Will codes report it bout check engine light? I've got a reader, but the check engine light hasn't come on through the whole process.
Expert:  fordtechsuzukitech25 replied 1 year ago.
there are a lot of codes that will not make check engine light come on, can you monitor any PID'S with youre code reader
Customer: replied 1 year ago.
P1151 Air metering and P0171 System Too Lean (Bank 1)
Expert:  fordtechsuzukitech25 replied 1 year ago.
can u look at or monitor any data
Expert:  fordtechsuzukitech25 replied 1 year ago.
i looked up p1151 and it instructs me to look at oxygen sensors first then mass air flow and then fuel injectors
Customer: replied 1 year ago.
Ok, I'll give a look at the O2 sensor(s) and see what happens before I tackle injectors.
Expert:  fordtechsuzukitech25 replied 1 year ago.
i hope everything works out for you