Alright guys I have an '88 XLT, manual and 4x4, and I'm stumped. 2 days ago on the way home shifting into 2nd gear (and almost every gear after) it would not get up and go like it should. I would be nearly wide open and it was struggling to go around 2000rpms. It was acting like it was starving for gas when trying to accelerate. Anyway, I clutch in and the idle falls and fluxes between 400 and 600rpms like it was going to die but fighting to stay alive. I've read threads similar and they suggested to change a few parts, which I have. I've changed the fuel filter, air filter, distributor cap and rotor, and plug wires. The night I changed the cap and rotor it ran fine and the next morning it ran fine for a bit but then ended up doing the same thing. Any help would be greatly appreciated!

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Check ur o2 sensor. Might have 2. Had exact same problem. Mines got 1. But I have a modified exhaust so idk if you'd have 2 or not. But u can check it by unplugging it. If it fixes the problem when unplugged that's it. Located on exhaust.

Thanks for the suggestion man. I removed it and cleaned it a few days ago and it didn't help. Last night I cleaned the throttle body and so far no problems. I ended up ordering a new sensor anyways. It's not like it can't use it.

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Check your MAF sensor.

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Considering 2.9 --> 4.0 conversion? Shoot me a PM.

I am having this same problem on my 86 4x4 2.9lt and I was going to clean the mass air flow sensor but I don't see on on it at all. I just bought this truck as a project and may have bitten off more than I can chew. Thanks XOXO!

Thanks for the help guys. I don't have a MAF sensor though, I have a MAP sensor and that was one of the first things I changed.

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Just an update (after a month, I know) but here is a list of all the things I did.
Changed: O2 sensor, ECT sensor, cap & rotor, plug wires, MAP sensor, TPS sensor, IAC valve, fuel pump (in line & in tank), fuel filter, air filter. (Might be missing things. It's been a long process)
Cleaned: throttle body. This was the biggest fix. I pretty much gave it a bath in cleaner and that helped the most.
Other: re-gapped spark plugs
And after all this I still have a CEL. So that's my next adventure.

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Glad u got the problem mostly fixed. I have a CEL also. But truck runs perfect.

Same with mine, it runs perfect. The upside is I have two years til my next emissions test so I have plenty of time to figure it out.

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I replace the fuel pressure regulator on my 2.9 v6 and it resolves all of the rough idle, power loss around 2000 rpm, and running rich problems. The original 25+ years factory installed part pours fuel out of the regulator's vacuum tap. The fuel pressure regulator is strictly mechanical. The vacuum line runs from the regulator back side directly to the intake manifold. If the regulator fails, then more fuel is pulled directly into the air, enriching the fuel / air ratio. Plus, the engine computer has zero chance to control and prevent this situation. All it knows is that the engine is running rich.

You will need a special fuel line tool to disconnect the main fuel line from the regulator. In my master fuel line and A/C kit it is part number 519154. To relieve fuel line pressure, there is a Schrader valve cap about four inches in front of the fuel regulator. The Schrader valve may be hidden by the fuel lines. The regulator is on the driver's side of the intake manifold, in front of the distributor. Please do this part swap on a cold engine. Fuel may run down to the exhaust manifold.

I hope this resolves your engine's problem, like it did with mine. It is great having a 25+ years old Ranger running like it is fresh out of the factory!

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1990 Ranger XLT Super Cab
2.9 L V6
5 speed Manual Transmission
4 x 2
Glasstite Topper
215/65R15

Hi names Greg I bough a 91 4x4 2.9l with 270 k needed 1 injector tune up and seals. Ran good most Time. had power loss once in a while. So I took roll bar off. It rained a couple o nights long story short truck still ran off and on and idled good sometime stalling running rough. Ended up with a lot of water in gas tank. I found out by syphoning some out with a small hose. -----fill hose had a hole and a large crack. Runs great now. ---------- Hi Greg again. I had the exact same issue on my 91 ranger.

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Collierdog.