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Discussion Starter #1
1991 mustang LX 5.0 240,000 miles. Stock long block and 5 speed trans, all else modified, including griggs full street suspension.

I am new and this is my first post, thank you for your help and suggestions.

I have had a major loss of power in WOT situations, usually in 1st gear. Over the last few years, the frequency of the problem has gone from to rare to often. I have listed things that I have done or are on the list to try. If I take the cap off the distributor, is there a way to check the play as you try to wiggle the shaft, to determine if the play is from a bad distributor or a slack timing chain? What is the next best step?

- vapor lock ish/loss of power possible solutions

- Replaced/upgraded

fuel filter - changed - helped some

fuel pressure regulator - replaced with adjustable, set to 40 psi min stock setting - helped a lot

fuel injectors - replaced stock 19lbs with ford racing 24lbs - done with fuel regulator and BBK mass air meter - helped a lot

Cold air intake path - had moroso, replaced with a BBK when new mass air meter did not fit well - helped some, done after the above

- Never touched

fuel return line - stock fuel lines in place

distributor - stock

ignition control (TFI) module - stock

- Replaced previously

timing chain - replaced with ford racing chain set 100,000 miles ago - restored lowered power levels I was experiencing at the time

cap and rotor - historically helps some when replaced, replaced frequently

spark plugs - historically helps some when replaced, replaced frequently

ignition coil - historically helps some when replaced, replaced frequently

ignition wires - historically helps some when replaced, replaced frequently
 

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Have you checked your fuel pressure? Could be a weak pump perhaps. Does it flatten out like you hit a wall?
 

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Discussion Starter #3
I replaced the fuel pump with a BBK 225GPH pump, no difference.

Funny you should mention that. I have had a high pitched wine in my fuel pump since the car was new. A couple years ago, when the problem was less severe, I replaced the fuel pump with a BBK 225GPH pump, no difference.
 

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I meant 255GPH, and I also just increased the pressure at the fuel regulator and now I get some backfiring, which I think indicates too rich a mix ???
 

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A ri h mixture can cause a backfire, but what is.your pressure set at? If its at 40, i kinda doubt its from that, backfire could also be an ignition problem. What is your timing set at?
 

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Discussion Starter #7
I pushed the pressure to 60, then the backfiring started but the power loss is less frequent. The timing should be 10, but I have not checked it for a while. I will confirm sometime this weekend.
 

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When you say wot,do you mean pedal is to the floor and/or do you mean rpm gauge is at redline,etc......I believe the ecm has a cutoff point of 6250 rpm in which reaching or goin past that limit causes the car to lose power.The ecm either shut downs or alters the fuel and/or ignition for the purpose of not over revving the engine.You probably know this already though
 
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