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1997 Ford ranger

Old 01-12-2019
lane5186's Avatar
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1997 Ford ranger

I have a 97 Ford ranger that has a bad miss in it. I just changed the new coil packs plug wires and plugs and it still running rough and ideas on what is wrong with it
Old 01-12-2019
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Coil Pack(s) so I assume a 2.3l 4cyl engine?
Not a V8(also used 2 coil packs)

Misfires on this 4cyl engine usually isn't from a spark issue, each cylinder has 2 spark plugs and BOTH fire at the same time, so BOTH would have to fail.
In a regular engine with just one spark plug in each cylinder then changing spark plugs would be the first thing to do

In any case you have changed them and still have the misfire, so next step will have to be a compression test, which would have been the first thing to do on this model engine
You need to remove 1 spark plug from each cylinder, the easiest to get to, which is none but still needs to be done, lol.
Then use compression gauge in one cylinder at a time, hold gas pedal down to the floor when cranking, that shuts off fuel injectors and gives engine maximum air, need at least 5 "hits" of compression stoke to get valid reading
Write down results as you go

1997 2.3l SOHC Lima engine should be in the 160-170psi range
If you find one that low, i.e. 3 at 165 and 4th at 120, then put a teaspoon of oil in the spark plug hole and retest compression
It will go up, but by how much will tell you if its ring or valve problem, if it jumps to 150+ then it rings, if it stays under 140 then its valves

Rings are not likely, usually its a burnt exhaust valve or tulipped intake valve
Could also be valve train issue, rocker has moved and either not opening valve all the way or not letting it close all the way

Compression is either good or bad, hard for it to be intermittent, which is why you do this test first, take it off the table as the cause of the misfire or find out it is the cause and save yourself time and Money!, on non-fixes, you can chase your tail on spark and fuel when it was a compression issue, I know I did that many many times

You should have a code with the misfire, P030X, X = 1, 2, 3, or 4, which is the cylinder number
If you do you could try swapping injectors around, i.e. if you have P0302 now, and you swap injectors 1 and 2 around, and get new code of P0301 then replace that injector
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