I bought one off the side of the road for $650 recently. Same problems. Everything was still OEM, so I changed it all out. Top two or three causes for me were: Throttle position sensor: caused the accel. problem you speak of. Rough Idle and weak accel. when you wind out the gears: Idle Air Control Sensor or IAC. This made mine run like new. I had also replaced the EGR and MAP. My cat is also original, so that too will cause a chug, or miss, or even bad acceleration if it is really clogged. They're like 200 bux on ebay.

 

Truck runs fine when the temp is low (freezing) but acts up as described when the temp rises. I timed it, replaced plugs (wires look good), both fuel pumps and filter, changed the MAP, TPS, and dual contact coolant temp sensor, cleaned with lacquer thinner a dual contact sensor (not shown in my Haynes Repair Manual) located on passenger side of center vert intake pipe that was choked with a gooey tar-like substance. - no joy.

 

The problem is the fuel rail with this model. The aluminum acts as a heat-sink for the steel and we get good ol' fashioned Vapor Lock/sputter. Shield your fuel rail and you should see a difference. I stuffed kevlar gloves under mine and I haven't had to bleed the shrader valve once. I also run an electric fan to help keep my wee-beastie cool... 100 bux well spent!

 

You can also get a bigger radiator. It's expensive but well worth it when you get jammed up in city traffic. No more wear and tear on the starter...

 

86 2.9L Ranger - acceleration, power and bucking problems SOLVED.
I found and fixed my jerking, acceleration, and low power problems by doing a fuel pressure test. I screwed the fuel pressure gauge to the fuel rail Schraeder valve, ran it out the back of the hood and propped it so I could read it while driving. I put a block of wood in front to hold the hood open enough to not crush the hose and held the hood down with a bungee cord. The pressure at idle was 37psi with the vacuum line attached to the back of the regulator and 40 with it off and plugged. When I drove it, the pressure went down starting about 2,500rpm to 10 or less at 5000. I knew it had to be a flow problem - the rail pump, or a blocked or kinked fuel line. There was a bent fuel line right where the line attaches to the fuel rail. The line is fairly rigid plastic and when it got bent it stayed kinked so it reduced fuel flow at higher rpm demands. It was barely visible because the fuel line is encased in black foam tubing. I cut the tubing away, cut out the kink, reattached the line and all is well.

 

so i have an 86 ford ranger and it has a 2.3 l inline 4 and a 5 speed manual. i recently fixed a timing issue on it and when i try to get to highway speeds i can only get up to 55-60, less on up hills. any ideas on what it might be.