94 Ranger 4.0L runs rough when first started - Ford Powerstroke Diesel Forum
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Old 04-13-2010, 02:08 PM
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94 Ranger 4.0L runs rough when first started

My little 94 Ranger 4.0L with around 220,000 is getting to where it runs rough when first started, especially when the engine is hot. It even dies sometimes. The idle seems kinda erratic too. After a minute or two it will usually settle out and run and drive just fine. It will also usually act right when returning to idle after driving. The idle does seem a little high and occasionally under full throttle it feels like it might miss a lick or two. Still gets consistent 21 mpg, last fill up was 18 mpg but I think that I forgot to trip the odometer or something.
Where should I start looking?
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Old 05-03-2010, 06:34 PM
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Lightbulb

I would check the 02 sensor and the connections to them. I have a 97 4.0 Ex and i've had to replace several. They can cause a horrible idle and missing because of the way their reading is mapped into the fuel table (from how it was explained to me). But other than that, mine's been bulletproof aside from a seized idler bearing removing the pulley and taking the belt with it If the O2 sensors check out, you might try the usual IAT,IAC, and MAF cleanings in addition to a basic spark plug check. Also, if memory serves the 91-94's have trouble with plastic cracking in the coil pack which could also cause this problem.

Sorry for the long post, hope it helps.
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Old 05-04-2010, 02:33 PM
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My girlfriends 01 Escape was doing something similar to what you are describing.
I changed Plugs and wires, MAF sensor, IAT sensor, and TPS sensor nothing seemed to fix it.

The mechanic was wanting to change out all of the Injectors (it was still throwing fuel codes)
I still wasnt convinced that was the problem.

A few days later I had myself a bright idea and decided to change out the upper and lower intake gaskets, ran like a top after that
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Old 05-04-2010, 03:08 PM
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Vacuum lines are another thing when it comes to a rough erratic idle. Had a 4.0 a long time ago and that was exactly what it was. Could be any number of things.
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Old 05-04-2010, 05:27 PM
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If the op had an sohc from late 97-up the intake would be most likely, however this is one of the more bulletproof ohv's. Vaccum lines would also present other problems not just a rough idle.
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Old 05-05-2010, 01:08 PM
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I'm going to start with new plugs and wires, the ones on it have about 50K on them and were installed in 2002. If that don't work then I will move on to more complex stuff.
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