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Old 04-22-2015
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97 Ranger 3 cylinder misfire

97 Ranger
2 wd auto v6 3.0

This is my first time posting and I really need some ideas fast. Thanks.
I bought my fathers 97 Ranger wanting to fix it up since it was mechanically very reliable and has a solid frame, just needed some serious bodywork.

So I have a weekend newspaper delivery route that takes 2 days, covers 300 miles and 2200 papers. So we were going right along good last week and all of a sudden the truck lost alot of power, the check engine light started blinking, started running really rough, and sounded about the same as if the muffler was off.
So after pulling over and realizing it was misfiring I went home changed the spark plugs and spark plug wires. It might of gained a tiny bit of power but ran just as rough. I pulled each wire from the ignition pack and there was a spark jumping to the ignition pack on all 6. So I took it to Advance Auto and checked the check engine light on the computer. It says it is misfiring on cylinders 3, 5, and 6. and o2 sensor #1 is bad. Which I already knew about the o2.
So I had to finish the route as is, it did fine but definitely ran rough. I just ease up whenever the light starts blinking.

So I have only thursday of this week to fix whatever is wrong and don't know where to start or what else it could be. We have only the 1 vehicle running and our newborn in the NICU at the hospital so its getting complicated. I do have a vehicle I can borrow for the first day but need to have it fixed by sunday or drive it like that again.
At this point changing the wiring harness is about all I can think of.
Any idea's whatsoever will be greatly appreciated! Thank you, Teddy Chase

also, it is obviously not the greatest idea, but will I likely do any serious damage if I am forced to deliver again on 3 cylinders?
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Old 04-22-2015
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Well in my experience when you have multiple misfires like that its usually the coil pack. A compression test probably also wouldnt hurt.

Last edited by vista4.0; 04-22-2015 at 10:37 AM.
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Old 04-22-2015
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When was the last time you got gas in the tank?
Could you have gotten some "bad gas"(high water content)
That could have started the misfires

On a '97 3.0l the ignition control module is in the Computer, so not much you can test there.
Ford cylinders are numbered like this:
3 6
2 5
1 4
Front

The Coil Pack is control by that module in the computer and it can be tested but first double check the wiring on the coil pack, it is "tricky", lol

3 4
2 6
1 5
Front

So...1, 2, 3 easy peesy
BUT 5, 6, 4, easy to screw up

Firing Order 1-4-2-5-3-6
So your misfires only have the one thing in common, last half of firing order, 5 - 3 - 6
Make sure 5 and 6 are not reversed on coil

Coil packs are expensive, you can get them at wrecking yards and they don't fail that often so a used coil is not a bad bet.
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Old 04-22-2015
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Thanks for the replies,

I put the cables back on one at a time to be sure I didn't mix them up, and after looked up a chart online to check for sure. I don't think that could be it.

I knew I wouldn't have enough time to make it to the Pick N Pull before weekend so I just bought a new coil pack today. It seems to be running just about as rough and still misfiring. My father has a compression tester but I won't be making it out until probably friday to check that out.

Does anyone have any opinion on if it might be a bad wire in the wire harness and if it would be worth the $40 to try a used one? A friend says to take my multimeter and find the bad wire but I don't know the first thing about how to use it since it has so many settings.

Also the misfire could be from the fuel injectors couldn't it? If so where should I start there? I don't know much of anything about fuel injection, never had to fix any yet.

Any new idea's are greatly appreciated!
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Old 04-22-2015
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I have been doing firing orders for over 40 years, I still goof up, double check it then have a friend check it, lol.
Chased my tail for hours on that mistake.


To test fuel injectors, unplug coil pack's 4 wire connecter so there is no spark
Crank engine a few times
Pull spark plugs one at a time to see if the end is wet with fuel.

You can also wait and do this test when doing compression test, remove all spark plugs for test, as usual, wipe off the end of compression tester, DO NOT prop throttle open.
Install compression gauge and crank engine, make sure you get 3 or 4 compression "hits".
Check gauge, write down cylinder and PSI number
Remove gauge and check end for fuel, if fuel is present then injector is probably OK, wipe off end and test next cylinder.


No on the bad wire.
There are 3 coils in the coil pack, each coil sparks 2 spark plugs at the same time(waste spark system), a coil can fail to generate enough voltage to spark both, but new coil says that isn't happening.
3 of the 4 wires on the connector go back to computer, each controls 1 coil in the pack, if 1 wire was bad then that coil wouldn't spark, other 2 would
Coil Pairs are:
3 4
2 6
1 5

Look familiar......so you have 1 cylinder from each of the 3 coils misfiring, so......


Each fuel injector gets 12volts when key is on, but has no Ground so stays closed.
Each injector has it's own wire(so 6 wires) running back to the computer, computer Grounds that wire to open injector.
For 3 of the 6 wires to fail would be totally against the odds.

Last edited by RonD; 04-23-2015 at 09:23 AM.
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Old 04-23-2015
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Ok, thank you. That makes alot of sense. I will work on it again as soon as I possibly can and let you guys know. Thanks
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