I have a 97' Ranger that is doing something weird.

Over the past year, my Ranger is pulling codes periodically. It the past year I have put on so many new parts only to have a new code appear in less than a month. Some of these codes are the same codes as the new parts were put on.
I have had P0171, P0700, P0756, P0102, P0135, P0430, P0303, P0305 and P0306. There are more but these are the ones I remember.

Yesterday, on my way home from work, the engine light come on and the truck started running really rough. I now have the codes: P0303,P0305 and P0306. This is odd because I put a new coil pack, wires and Motorcraft plugs last summer.
The overdrive button quit working yesterday as well. I need this to work as I have to pull an enclosed trailer. Luckily the trailer is at the jobsite and I was not pulling it home yesterday.
The truck runs like a champ before a code appears and they appear out of nowhere. I am starting to wonder if the ECM is bad.

Would it be wise to pull one from the same make and model and try it?
I have seen and heard different opinions on whether the swap would work or not.

1997 Ranger XLT 4.0
Auto Trans
4x4
VIN: X

 

Certainly possible

1997 4.0l automatic is all that matters, ECM is same for 2WD or 4WD and any other options

Except for P0171 and P0430 the other codes could be wiring related, look for rodent chewed wires

P0430 should only come up on a DUAL exhaust which you probably don't have, so would point to an ECM issue not a vehicle issue
P0430 drawing: https://g35driver.com/forums/attachm...used-banks.png
Bank 2 sensor 2 in blue is the P0430 code
Single exhaust only has bank 1 sensor 2, which is P0420

And the misfire codes are for all 3 coils in the coil pack, so again more of an ECM issue, probably fuel injector issue on 3, 5 and 6 not spark or it would effect other cylinders, each injector has its own wire from ECM

You could test compression on #1 and #5, easy to get to, and see if #5 is much lower, indicating a mechanical issue

Did the OD light ever come on with the codes or flash?

Did the CEL ever flash?

 

It was the P0420 code. I accidentally hit 3 on the keyboard in a hurry to type....sorry.

I didn't notice the OD light flash or come on. The only reason I noticed the OD button not working is when it started running rough and would barley take off from a stop. I tried to turn the OD off until I got up to speed then turn it back on.The OD switch may just be a coincidence but I do know it worked on Monday.

YES to the CEL light flashing.
It stayed on while driving but flashes when slowing to a stop, while stopped and at take off. When 45 pmh (around) was reached, the CEL would quit flashing and stay lit.

Something else to inform you of,
I disconnected the battery and removed the ECM do get the numbers from it. It was out of the truck.It was an hour before I put it back in. When I started the truck, i didn't idle rough or and very little gas smell/white smoke coming from exhaust. I took it for a drive (about 2 miles) and it didn't run anywhere near as rough as it did yesterday.

 

Flashing CEL means Misfires are happening right then and that would set the codes

So it only happens at idle, decelerating flashing CEL wouldn't make sense because injectors are off so there would be no firing so no misfiring
One of the benefits of fuel injection is that when you take your foot of the gas pedal TPS voltage goes down and computer shuts off injectors until RPM are under about 1,300, then it starts them again at idle level, Carbs just kept on feeding in gasoline

If possible I would test compression on 1 and 5 just to see if there is a problem there, if there is then doing other things would just be a waste of time and money

 

I did a "dry" compression test on all cylinders.

#1: 170 #4: 150
#2: 165 #5:170
#3: 150 #6: 170

170 is the highest so I multiplied by .15
170 x .15= 25.5 ( I rounded up to 26)
170 - 26= 144

My lowest is 150

Should I do a "wet" compression test?

 

My 1994 4.0l with 400k tests at 155-165psi for all 6 cylinders


I would wet test #3 and #4
If they don't come up to above 170 then its a valve issue

You can wet test any of the 170 cylinders to get its increase for comparison

P0303 makes sense but not P0305 and P0306

Not a big fan of the 15% rule, 10% is what I have always used, but compression test is done to see the differences on that day with that gauge and that battery(crank speed)

Your average is 163psi, so 150 is 13psi below average 170 is only 7psi above average

 

How much oil should I use for the wet test?
I've read different things, some say 1-2 tablespoons and some say not to use over 1 tablespoon or it will give a false reading.

 

I use a plastic straw, i.e McDonalds drinking straw

Dip it 1/2 way in a oil bottle, then put finger over the end
Lift it out and put it down spark plug hole, remove finger

Never measured how much that is but its enough and not too much, lol

But yes, 1 tablespoon more or less would be correct

The oil seals the piston rings better, so pressure ALWAYS goes up
If it goes up to a "high" cylinder number, in this case 170+ then rings are leaking too much
If it just goes up 10 psi or so then its valves that are leaking, the oil doesn't help seal the valves, only the rings

 

The readings in my last post were incorrect. I borrowed a compression tester from a friend and it was inaccurate to say the least.
I bought one and here are the results of the "dry" test:

#1: 180 #4:150
#2: 180 #5: 180
#3: 160 #6: 190

I "wet" tested #3 and #4 with 1 tablespoon of oil.
#3: 190
#4: 160

So I have leaking rings in cylinder #3 and leaking valves on cylinder #4, is this correct?

 

Yes, that's what it reads like

 

The head work I can have done pretty cheap as I know someone that does it professionally.

The leaking rings are a different story.

The truck has 254,xxx miles on it.
So is is unfeasible to tear the engine apart just to replace the rings. Also, there is the possibility that the cylinder itself is the culprit.

I really love my Ranger. That being said, it's clouding my judgement on how to proceed.
I don't have money to waste so I really need some advice on what to do. Sell it, rebuild it or buy a new motor.
The transmission is the original so would I have to rebuild it as well if I put a new or rebuilt engine in?

Also, what about using the Restore Engine Restorer? I have seen ALOT of good videos and reviews about this product. I'm not a fan of these "magic in a bottle" type products but, is it worth a try? Would it do more harm than good?

 

Yes, hard call
Engine additives are fine to use/try

4.0l OHV, VIN: X, was last used in 2000 Rangers so won't be alot of low mile used engines around

You can call local machine shops and see what they would charge for short block rebuild and head rebuild, or long block

You should have the 4R55E automatic, last year in 4.0l, 1998-2000 used the 5R55E but you can use these in a 1997 4.0l 4x4 since speedo VSS is on transfer case not transmission
5R is the same as 4R inside and out
Yes, at 250k, if trans hasn't been rebuilt before, its closer to the end than the beginning

If you can find a rusted out 1995-2000 4.0l 4x4 Ranger, or Mazda B4000 4x4, automatic with lower miles you could swap power trains, use your transfer case if 1998-2000