Galloping Pony Stumbles

I have an '89 5.0 5-speed Mustang GT. Before I go further, I did have a similar post out here a while back. Please stay with me though. During full throttle acceleration in first gear it starts stumbling well before red line ... by 3,500 or 4,000. It's like it runs out of gas. Yet it's fine at part throttle (just did this today) right up to 5,000ish with no problem. It's fine in second gear at full throttle all the way up to 5,000 and beyond. It only stumbles at full throttle in first gear.

The fuel filter and fuel pump have been replaced. I've checked for codes. I've checked the TPS. I have no clues. It runs perfect except at full throttle in first.

Ideas anyone?

Thanks very much! Dave

Reply to
Dave Wick
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Fuel pressure regulator?

Shot-in-the-dark mode;

You say that you replaced the fuel pump. It sounds like you might have fuel starvation under heavy acceleration. First gear should pull more acceleration G's than second. maybe fuel is running away from the pickup? Try it with a full tank of gas. (?)

Dave Wick wrote:

Reply to
cprice

" snipped-for-privacy@here.com" wrote in news: snipped-for-privacy@here.com:

Also maybe coil... though MOST times that symptom is very marked and exhibits in all gears.

SITD #2

Reply to
Backyard Mechanic

This idea is based on the assumption that the engine will "c*ck" to one side more in first than any other gear. I don't really know if this is true. It's a guess. If it does, a bad spark plug wire is grounding out against something when the engine is "torqued" to the max, but not when under partial torque (less than full throttle in first or full throttle in any other gear). A new set of wires may solve the problem.

Comments on my assumption may help Dave out.

Reply to
John

Interesting thought. I'd like to think that a careful inspection of the wires should show any issue. I'll have to take a good look.

Dave

Reply to
Dave Wick

Its been quite awhile, but isnt there a metal baffle of sorts that floats inside the gas tank? I seem to recall that the fuel pump pickup fits inside/between the baffles somehow. I also seem to recall that I read that if the pump pickup wasnt installed correctly in the baffles fuel starvationc ould happen. (?)

Like I said, its been a long time since I did a 5.0 fuel pump, so I might be confused.

Reply to
cprice

Pop the hood with the engine running in a dark place. You may see some arcing.

Reply to
John

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