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I have a 1986 GT 5.0 HO motor and i just put new head gaskets on well took me a few trys to do the valves but any ways i took it out for a spin and it ran a little rough at first then at 35 or 40 it smoothed out and ran great pulled up at a friends **** it off well when i got back in it and sta:smilierted it,it died when i gave it gas it had really good fuel presure, let it set for about an hour then it started i could fan the gas and it would go but if i pushed the gas pedal down it wanted to die but letting off the pedal would seam like it would get fuel. If there anyone that could HELP me find and fix the problem with my mustang i would greatly aprechate it. MY GIRLFRIEND THINKS IT A PIECE OF JUNK. I LOVE THAT CAR AND CANT WAIT TO DRIVE IT AGAIN. THANKS
 

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You seem to have one of those fun problems. If you took it all the way down to the head gaskets I can think of a few possible problems just going by the systems that were disturbed.

1) Possible vacuum leak. The easiest way I have found to check this is a can of carb cleaner and lightly mist it around the engine bay and if the idle picks up you have a leak somewhere. I have an 86 as well and it has a ton of vacuum lines that tend to get brittle.

2) Throttle position sensor. This will be the little black thing that goes over the shaft for the butterfly on the throttle body it has 2 bolts and if I remember right 2 wires coming out of it it needs to be set right for the computer to know whats going on.

3) You say you have fuel pressure, where is it being checked from? Possible that something is not hooked up quite right and it has a leak somewhere.

4) Do you have the rocker studs that torque down? There are two different kinds of rocker studs (at least that you will encounter on a stockish 302) fully adjustable such as what you will find on a 350 Chevy where you set the "lash" by compressing the lifter plunger slightly or the ones that torque down this will be a stud that has a shoulder right after the threads on the rocker stud. Stock should be the latter. If you didn't bleed down your lifters prior to torquing the rockers I could see how you may have gotten an incorrect torque reading and may have a rocker arm flopping around at higher engine speeds.

5) You say it took you a few tries to do the valves? What do you mean do the valves?

In the carb world which I am more use to (my 86 is the first FI engine I have messed with) when an engine does what you explain its getting to much fuel as in to big of an accelerator pump or squirter or the secondaries coming in to quick.

I don't know if any of this will help you or not but hopefully it will.
 

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It's a long shot but check your Map sensor hose while the engine is running. I had a similar problem on my '86 and it turned out to be the map sensor hose closing up while it was running- losing all power when you hit the gas but running fine at idle.
 

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Did you pull the distributor when you did the head gaskets? Is it in correctly? One tooth off and you've got timing issues. That and firing order....happens all the time.
 
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