92 Ranger 3.0 engine miss at hwy speeds

[BltFdTuff]

hi, trying to find a solution to this problem:
truck has 3.0L , 170,000 miles, automatic. Runs fine, no hesitation until I get up to about 55mph and then it will intermittently miss or cutout. I can hear what sounds like a vacuum leak (maybe), or could be ignition but does not do it under 55 ever. Replaced IAC, fuel filter. Seemed to improve with gas treatment but the problem seems to have something to do with the speed.
No check engine lights or idle problems-fuel pressure checked out fine. Hoping maybe someone out there has an idea. Still an excellent truck, was obviously built right!

 

[JP02XLT]

How old are the plug wires? could be missing under load.

JP02XLT

 

[Runnin'OnEmpty]

Yep, that would be my first guess too; first step
would be to replace the plugs and wires.......

You'll probably find some of the plugs with
a very wide gap.

 

[BltFdTuff]

Thanks, could the coil also do that? I had a friend who had a Maverick that would run fine up to about 55 or 60 and then simply would not go any faster. It was the coil.

 

[JP02XLT]

Generaly not, a coil usually fires or not & on these trucks it would drop 2 cyl at a time. Try plugs & wires first

JP02XLT

 

[Big Jim M]

Tuff You think you hear a vac leak... Could that be the exhaust pipe whooshing or whistle'n? A partially stopped up exhaust system will cause similiar problems as you describe.
Big JIm

 

[evanesce69]

ditto the miss under load