I have a CEL. Engine misfire in first 1000 revs. Have already changed air filter, plugs and wires, both O2 sensors. Problem persists. Very low and rough idle. Low power and struggling to get to highway speed. I had a tech check it with his diagnostic tool and everything passed. Injectors, MAF the works. The engine has 164K on it and the front timing chain is spanking in good shape. I went old school and checked the plugs with a timing light. It appears that #1 is firing intermittently. To say that I am frustrated would be an understatement. Ready to sacrifice a live chicken unless somebody else has a better idea.

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'03 4X4 XLT 4.0 SOHC
No Mods, 2 Meter VHF Mobile Radio

Have you checked the timing sprockets? The chain may be in good shape but that's not worth anything if the sprockets are crap. This happened to mine and I had a misfire in 1,3, and 5. Insane I know. And I had about the same problems as you; kicking, rough idle, very little acceleration had to floor it to go up 5mph

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2001 Black Superman Ranger Edge, 4.0 SOHC, Automatic, Side Step, T-bars cranked, grille guard with two 55W lights, factory bedliner, light rack with four 100W off road lights

What codes are you getting?

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2010 Ranger XL 2.3L 5 Spd 3.73:1 Bone Stock
2013 Scion FR-S 2.0L/H-4, 6spd, 4.11:1 Fast Enough Stock

I haven't dug in to the internal engine components yet. I haven't rechecked the codes in a little while. Early on, I had a misfire code and a left bank too rich code. I couldn't find any vacuum leaks so, I changed both the O2 sensors. That didn't help much. I'm going to clean the throttle body in good shape and recheck the back side of the engine for vac leaks one more time. I'm really starting to think this motor has got to come out for a new timing set. OUCH!

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'03 4X4 XLT 4.0 SOHC
No Mods, 2 Meter VHF Mobile Radio

yeah timing isnt something you wanna mess with. i had a lot of trouble with mine because not many mechanics wanna work on this type of engine

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2001 Black Superman Ranger Edge, 4.0 SOHC, Automatic, Side Step, T-bars cranked, grille guard with two 55W lights, factory bedliner, light rack with four 100W off road lights

I'm trying to explore all options. Considering the cost of a complete timing set AND the special tools required to perform the repair, it's almost the same as a salvage motor. Getting the work done at a shop is out of the question. I've even been researching a 5.0 engine/xmsn/xfer case swap. It's tempting

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'03 4X4 XLT 4.0 SOHC
No Mods, 2 Meter VHF Mobile Radio

1)check coilpack
2)change fuel filter and test pressure
3)get a code reader and check for codes/pending codes. if you have android phone you can turn it into an excellent scanner for $20
4) add techron to the tank....injector?

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forget # 4....... I see you had the injectors tested.........I would pull the IACV off and clean it up

New fuel filter installed the same time O2 sensors were replaced. Didn't check pressure. I'll have to read up on testing the coil pack. I might have a chance to run out and check codes later today. As for the IACV, I was kind of suspicious of this component as well. The used to start instantly. Now, I have to try a couple of times to get it going and the idle RPM is low. Thanks to all for the input. I'll keep you posted.

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'03 4X4 XLT 4.0 SOHC
No Mods, 2 Meter VHF Mobile Radio