FoxGT

Question from a friend:
My '86 Mustang GT is missing at high RPM. It starts missing at about 3500-4000rpm & it keeps getting worse. It won't rev over 5000rpm anymore.
It all started at one instant, not a gradual thing. I had got on it a few times earlier that night with no problems, it pulled strong all the way to 6500rpm. The first time it did it was when I was leaving a stop sign I was at full throttle & it wouldn't burn out, it usually smokes the tires easily all through first. It was making a sound like it had a big load on it, like the way it sounds when you try to climb a hill @ full throttle in 5th gear. It also sounded like it was backfiring alot.

Edit: it will rev to 7000 when in neutral

86stanggt

sounds like your timings got changed

jhogan2424

yeah, could be the timing... Or, something in the firing. Check everything that has to do with firing. Make sure you don't have a plug wire or two laying against a header. Also, check out the coil wire to see if it may be grounding on something. Maybe even as simple as a rotor button inside the distributor. Check all this and get back, Jason

lukejohnson7295

I had the same thing in my 86' GT. I had stock wires resting on the headers that were worn thin a little bit.. Then I was working in the garage with dim light and could see it arc a little bit.. bought new MSD wires and coil. made sure they weren't touching headers. Night and day difference.

69mach1377

Check your cap and rotor also...

vfast

well your foot is one problem reving 7k out of gear= boom....wouldn't surprise me if you bent a pushrod or hurt the valve spring.....first look at the fuel filter

Quik

you taking it that high with a stock motor is bad. chances are valve floated and possible damaged a pushrod or colapsed a spring.

also check to see if any plug wires are against the headers. also check the fuel filter

guess what when you took that motor to 7k you kinda ran it without fuel. stock fuel cut off is 6250 thats when it cuts fuel

vfast

OH..ok now your repeating me

95_302_StangMan

someone is trying to wreck their engine.

paulstang

lets see how high we can rev our motors before it blows