Ok I've got this 98 Ranger with the 2.5L and the 4r44e automatic. The engine is used and has about 100,000 miles now and is it a good state of tune - so I think. The transmission was a remanufactured I bought a few years ago that was built with the shift improver kit, Kevlar bands, extra planetaries, 4wd pan, and external cooler. It's now got 92,000 miles on it and it's been serviced every 30,000 with a fresh 4wd filter and Mercon V fluid. It's outlasted the last 3 transmission I've had in my Ranger. I've got 315,000 miles on the body. For awhile it was randomly losing power while driving like it wouldn't shift, almost like it dropped a couple cylinders, then as you kept your foot on the gas it would recover and rev up and shift. Then sometimes randomly at stoplights it would shake at a stop and have no power at take off until it hits 30-40 mph. Sounds like a converter, is what I thought. But now it's doing it more often but not the shaking at stoplights as much as randomly losing power while driving normal speeds. Last night I drove it about 50 miles after doing a fresh filter and fluid change and this time it did it so much it threw a code up P1131. Eventhough that's a O2 sensor code, could it be hidden by a transmission valve body problem? One transmission shop said it could be a valve hanging up just by me describing it to him. Could this be ignition or fuel related or is it all tied in with the transmission problem, if it is even a transmission problem?

 

The description to me sounds like the engine is missing intermittently. Is it possible you have some water in the gas tank? That will cause chugging, bucking, and very significant loss of power. It can also cause rough idle. You could put it in neutral and see if the roughness stops, but I'll bet it doesn't. EGR sticking and plug wires can cause similar behavior.
You can try manually selecting a different gear, which would/should make the transmission go to the geary you specify, such as '2', to see if the transmission is responding. I'd say you are giving it{trans} more than enough maintenance, so it should last if built well and free from abuse.
Shifting manually should get you to a lower gear without need to floor the accelerator pedal, so it would narrow the problem from engine to transmission... I think.
tom

 

may i ask a question? how do i find out what trannys in my 03 ranger and whether
its a 3.0 or a 4.0L ??
i have a chance to swap 4.0 & 5 speed into my 3.0 and don't know what will fit or what will need more stuff/wires/computors?? help, over head here!

 

I had a guy scan my Ranger with a scan tool and it tested everything more thorough than just retrieving a code. He determined that it was most likely a fuel problem causing that P1131 code to come up. It does it so randomly that I can't take it anywhere to get it diagnosed to a specific problem. I can drive 3,000 miles without it happening but it's happening more as I drive longer periods of time without stopping. It happened last night once on the way home from about a 20 mile round trip of non stop driving. So I let it sit overnight and then in the morning I did a fuel pressure test and let it run for about 10mins to see if it changed. It was dead on 65-70PSI which is what is stated in Ford's manual 65 +- 8 psi. I don't know if I stated it earlier but after that P1131 code came on the Check Engine Light actually went off and it ran fine and didn't come back on the next time it randomly lost power. I looked at the Ford's suggesstions on the code P1131 and it said it could be a vacuum leak,air leaks at maf, restricted air filter, pcv system, excess fuel pressure, leaking fuel injector, low fuel pressure, dirty fuel injector, vapor recovery system, stuck egr valve, leaking gasket. All that checks out ok except I don't know how to determine if a fuel injector is bad, what to do to test the vapor system, or how to test a stuck egr valve. I know those are two items that are original to the truck with 317,000 miles on them. The vapor system and egr valve. any suggesstions now?