any mustang 5.0 guys? i need help

[Vern]

heres the deal, i have an '86 GT 5.0 that a picked up last fall and its had a few little problems ive been workin on but it always ran fine until tonight. was out doin a little cruisin main then all the sudden the car just started missing bad. it seems ok when your idling and when your accelerating, but if you hold it steady like when your just cruisin the car starts to cut out and jerk like a sum beach its bad enough that it feels like someone keeps tappin the break while im drivin. it also seems to be worse the higher up in the rpms you hold it. when i got home i had it in neutral and revved it up to about 3000 rpms and held it there and it started cutting out and without me moving my foot the rpms dropped to almost 2000 rpms. also sometimes when it idles it will start revving up and down by itself and sometimes gets to the point to where it will peak at around 2000 rpms then drop low enough that it dies. oh and it only gets about 12 mpg, does that sound right? i think it should be gettin better than that my uncles got a 4x4 truck with the 5.0 and he gets better than that, hell my brothers got an 8.1 chevy that gets better than that. i was thinkin the cutting out could maybe be fuel pump or filter but wouldnt it cut out when you accelerated? this is my first efi vehicle and i dont know a thing about all this electronic crap and this is simple compared to todays cars.

sorry for the long post just wanted to try and cover everything.
thanks

 

[Fosgate]

Could be an air leak between the intake manifold and the throttle body. Distributor could need replacement or problem with the fuel regulator, injectors or pump. Could also be as simple as a loose spark plug, wire, or defective plug wire. Could be the EGT (usually a little green vacume hose connects to a little valve looking device, unplug it and see if it stops doing it). Could be O2 sensor needs replacing etc. There is so much it could be. I'd either buy the hand diagnostic computer for about $35 and look up the error code in a Chilton book or swing into your local ford garage and see if they could plug in a box and do a quick diag for a reasonable price.

 

[Vern]

thats what i figured, i was just hopin to get a good starting point to start lookin. thanks for the reply.

 

[IMSICK]

get in touch with TG800..... he his the mustang performance god

 

[Midge907]

Check out www.stangnet.com and look at there forums. Sounds like there could be many causes, so good luck. As for you fuel mileage thats about right for the city if you have lower gears such as 3.73's I dont even pay attention to the mileage in mine anymore.

 

[Vern]

Check out www.stangnet.com and look at there forums. Sounds like there could be many causes, so good luck. As for you fuel mileage thats about right for the city if you have lower gears such as 3.73's I dont even pay attention to the mileage in mine anymore.

thanks, i'll check that site out. on the gearing im pretty sure its still got 3.08's i never have to use 5th gear even doing 60 mph on the highway it only pulls about 2500 rpms in fourth. would like to have 3.73's though.