hello everybody. i posted this in the technical discussion (for the "other engines, 4 cyls) as well, but i figured i'd actually throw it into the ranger forum because it appears to get a lot more traffic.
I have an '01 2.5 5 speed, it misfires a tiny little bit at idle (if you let it idle long enough the CEL turns on with either a p0300 or a p0303, and it also lacks the power that it used to have.
i've replaced all of the spark plugs, wires, checked for vacuum leaks, verified proper fuel pressure and regulator functionality. decided to tear into it today to see if the timing belt had possibly slipped, but that's fine as well. listened to all of the injectors, and you can hear them firing (don't know if fuel is getting out, but you can hear them)
the one thing i did notice is that the plugs were a little whiter then normal when i replaced them, so my guess is that it's running lean, but why?!?
how man miles on it? what was the fuel pressure key on? engine running?. when did you change the fuel filter last? any maintenance done to it? how did you check for vacuum leaks? have you run fuel injector cleaner thru it? what about the air filter?k and n filter?
ps. did you swap wires to see if it still misfired on the same cyl. did you spray mist of water to see any sparks on wires or coil packs?
it's got 140k on it. fuel pressure was 60ish (IIRC) KOEO, and bouncing between 64-67 KOER. fuel filter was last done about 20k ago. been pretty good about keeping up with the maintence (except the timing belt ). i used a can of intake cleaner and sprayed it on any hoses/intake manifold) i could find to check for vacuum leaks. and no on the K&N filters, i know rangers with the MAF and MAP sensors don't like K&N air filters and i've swapped wires around, plugs around, just about everything i could think of to try to eliminate any spark misfire. still not too sure of the coil packs though...didn't go through any great lengths to check those out.
Maybe someone will chime in and answer this question. I looked up the fp and it says 57-72. koeo and koer but should the running one be higher then the key on one. it sounds like you eliminated a lot of things . the coil pack could be a suspect. I think you can swap the coil packs and if the misfire shows on a different cylinder. that would prob be your issue
I had a random misfire on my 99 with the 2.5. Never did get a code but i had a friend that owns a shop put it on his machine and my #1 injector was the fault. Sometimes it would fire, sometimes not. If the plugs are white, I would suspect fuel problem rather than ignition. If a coil pack was bad, one plug should be wet from no spark.
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