Maybe consider adding a 20oz Chevron Concentrate Plus at the pump to get good mixing, before filling up with Texaco, Chevron, CalTex, or now Shell, as those top tier fuels have Techron, or PEA already in them, so the additional 20oz of Techron will raise the treat rate 10X above the pump gas alone & can tidy up deposits on the fuel injectors, intake valves, piston crowns & heads, usually in one treatment.

So if intake valve deposits, or Combustion Chamber Deposit Flaking (CCDF) is the problem, this might make a positive difference.

Perform the daily 3 miles above 3600 rpm blow it out part of Fords 4.0L decarb TSB during the treated tank & use most of it up before refilling & see how it goes.
If it's intake valve deposits, or CCDF problem, this might make some difference.

I tug my bass boat over the Blue Ridge, on my way down to Smith Mountain Lake to bass fish, so I've use those fuels to keep my 4.0L blown out pretty good, as it has suffered from Combustion Chamber Deposit Interference (CCDI), so it gets the high rpm blow it out part of Fords TSB, going & coming over the mountains & has kept my CCDI knock in check!!!!

Keep us posted on how it goes.

 

Know Smith Mountain Lake..Used to go there when I was in Black Mountain NC. Back when I still had the 'F1 and the Flathead....Just didn't want to tow her to Fl. Stupid move. The beast is running a lot better..still has a miss at low rpm, but I haven't had the time to really blow it out yet. Trying to make a point of driving it every day, even if it's just till it heats up good. Wonder about additives to synthetic oils...since they are made for petroleum oils....Leaving 2nd Friday in Dec for Winter Haven.Full report on how the beast does as soon as I get back...C ya.

 

If your using a synthetic crankcase lube, you don't likely need to top treat it.

Auto-Rx is a multi-ester based recipe & is ok to use with a group-3 mineral based synthetic & still have it do it's cleaning thing. ARX needs to get good & hot to do it's best job & it'll likely get that on a good long tow.

They don't recommend using it with a PAO synthetic because competing chemistry doesn't allow the ARX to do it's best cleaning job.

Techron in the gas should tidy the intake side & combustion chamber up & may help, if deposits & or CCDF are the problem.

Will be interesting to hear how it goes, so keep us posted.

 

im having the same prob
idk what to do

 

OK> Ran the trip to Winter Haven....pulled the boat just fine. BUT!!!!! Now sets both misfire #4..and random misfire! When I start it, idle jumps to 2200+ and when it drops, drops like a rock. Sometimes it hangs a high idle when stopping for a light too. New TPS didn't fix...BTW, never going back to Pep Boys...tech lied to me about my brakes when I had tires put on.......I give up. Still runs rough, but not nearly as bad. Lost now, other than maybe have the heads done, or change the ECM ??????????????

 

On the idle speed hanging up on a stop, put the IAC high upon your suspect list. I know you said in a previous post that it was replaced around 30K, but my OEM IAC began acting out in less time than that. To test, disconnect it's electrical connector, go for a drive & see if the hanging high idle at a stop goes away.
If it does, suspect the IAC, if it doesn't, suspect a vacuum leak.

If you come to suspect the IAC, you might try pulling & cleaning it with a plastic safe spray cleaner like CRC QD, or MAF sensor cleaner & see if that gets positive results. If so, you'll know it's the IAC.
Cleaning might not last, it didn't for me, but was a good trouble shooting step.

On the continuning #4 miss, I was just reviewing your page one posts & saw that at one time you measured 140 psi on #4 & later measured 80 psi, so that & the presents of oil in that cyl, makes me want to suspect heavy intake valve deposits & maybe a CCDF problem causing an intemittent seal problem on #4, maybe along with stuck piston rings from carboned up ring lands.

SO, on the tow trip, did you treat the gas with Techron, or use a PAO based synthetic crankcase lube, or give it an ARX treatment, to try & tidy things up some????

 

It's been a spell, but I am back to report on The Beast...still is strange to crank it up and stand outside the truck and watch the idle go from 750 to 3000 rpm, and then drop back like slamming a door! Still has a miss and shake at low rpm but it no longer sets a code.Maybe the computer has figured out I am ignoring it and has given up trying to talk to me? But am driving it every day anyway.
Had to replace the upper control arms.Cannot understand why they would use something that cannot be lubed?? But the new ones have grease fittings.
I did use the Techron on the Winter Haven trip, and still have it in the tank. Ran it up to Eustis this month to Lake Yale, and to Lake Harris,still pulling ok.
Will not go back to Pep Boys , ever. Been going to them almost 60 years (My Dad took me when I was 2...) But I bought 2 tires for The Beast, and their tech was telling me the brakes were gone, and it needed new rotors and front wheel bearings.
NOT TRUE. Front pads looked almost new, the rotors are fine (I checked thickness and finish) and the bearings are fine.I don't like being lied to.Guess he didn't realize just how well I know the workings of The Beast?
I am out of ideas as to the miss at this point.Dealer sure isn't any help!

 

On the roaming idle rpm, have you done the IAC electrical connector disconnect test yet????
Or tried pulling & cleaning it with a plastic safe cleaner, to see it it'll have any positive effect ????

On the Techron fuel top treat, if #4 cyl deposits are heavy, you may need to try two treatments, with the daily blow it out accelerations I posted earlier & run most of each treated tank out.

Did you go to a high mileage recipe crankcase lube, or top treat the present cankcase lube with an additive, to try & address the #4 cyl oil useage & possible piston ring & valve stickng problems, from combustion chamber deposit loading, causing the compression # to jump around????

 

Two questions:

1. What year Ranger do you have?

2. What's the condition of the valves in cyl. #4? While you reported compression numbers, I still wonder if you have a valve or lifter problem.