Help solving 4.0 misfire/bog cylinders 1-3 mid throttle.

[PORTnPOLISH]

Hello, I have been reading through researching this issue since I developed this issue last week. I spent today trying to repair it but the problem only worsened and became a little stranger. Excuse my typing...its late and I smashed my thumb pretty good today and im typing this from my phone laying in bed.

PROBLEM:
I bought the truck and drove it home no problems but noticed I had a hard time maintaining speed but I figured it was going.to.take getting used to. I started driving back and forth to work 100% highway and halfway through the week I started working on my custom exhaust setup. Once I removed the muffler for measuring and I was driving to work the next day I noticed that a the problem of maintaining speed was worse and that it was popping and bogging while at mod throttle trying to cruise. Light or full throttle would kick back to normal.when going to wit the engine seems to really jump in power and the sound changed entirely. Through the week the problem got worse and worse and that brings me to today. I went to the auto store and picked up the parts for my exhaust and the repair items. After the repairs it was running better then ever for about a miles and then it got worse then ever and now will not even idle normally or under light to kid throttle. Will run great wot. Gas mileage is now terible I filled up th othr day and I've gone 140 miles and im on E!!! About 10 miles per gallon.

REPAIRS:
-fuel filter
- plugs and wires gapped to .054 (old ones looked all lean and were gapoped to .035
-cleaned maf with maf cleaner spray,maf was missing screws so I replaced them, I cleaned the seating area to assure no air leaks, fixed hose clamp on intake prevent leaks
-cleaned air filter...wasn't dirty
-tested tps ... good
-tested maf ...was good
-checked for vac leaks and found 0
- pcv valve vac.line was Willy and collapsed under vacuum so I changed it.
- seafoamed her with old plugs in

Some.things I found strange were that if I pull plug wires 1,2,3 I have puts of spark but the engine sound remains th same. Also when it "bogs" the engine noise gets quiet and looses power but when you go wot it gets power back and gets loud angain. You can play with it and maintain about 49 but it pops like crazy.

 

[hunter77]

hy this is the same thing that is going on with my ranger so far im thinking it is the egr valve senser but i havent been able to confer it if u find out wat is cousing your broblem pleas let me no ..thanku

 

[powerranger262]

I just had a similar problem and it turned out to be a cracked plug causing a misfire.

 

[PORTnPOLISH]

My next suspect is the egr. Im going to block it off to test it and if it solves the issue I will replace it. I just changed the sprark plugs out.

 

[PORTnPOLISH]

Also would like to add thee cylinder three injector has a loud tick. Maybe the fuel rail is contaminated? Not sure what would a seemingly lean condition but okay during wot.

 

[Earl43P]

If it runs well at WOT, there is an emissions system / sensor problem.

At WOT, the PCM/computer uses canned values and ignores the emissions sensors.

http://www.therangerstation.com/tech_library/OBD_I.html <that link will help you pull the codes from the PCM.

With your symptom, I suspect a dead O2 sensor on the passenger side. That's just a guess; you should get some codes out of that computer if it is running that badly.
Does the Check Engine Light come on when the key is turned to Run? (before cranking it over) If not, the bulb may have been removed or burnt out.

 

[Donnie strickland]

What Earl said.

 

[PORTnPOLISH]

The bulb is in fact burnt out. I am going to use my multi meter to pull the codes later on. I will check the 02 sensor voltages as well. I did inspect the wires and they are in good shape so its not a broken wire.
Yeah the pcm uses open and closed loop modes to determine fuel and timing curves. At least thats how my DSMs were when I was tuning them. I didnt think of that on my own though so thanks for reminding me.

Ill report back after testing the 02 voltages.

 

[srteach]

A bad O2 sensor will cause lean or rich almost all the time, depending on what section of
the sensor actually fails. The sensor should cycle from lean to rich readings at about 120Hz when operating normally.

There are three O2 sensors on that engine. One on each collector exhaust, and one post cat.

 

[PORTnPOLISH]

Yeah the second 02 is not there any more. thats how I knew the light wasn't working. i seen that there wasnt a rear 02 and there was no light on when I went to look at it. The front 2 are the only ones that determine fuel adjustments though. The post cat 02 is to determine whether the cat is still functioning.

 

[PORTnPOLISH]

Okay drivers side 02 was reading back and forth from .1 to .8 bit passenger never went over .2 so im going to grab one and see if it fixes it. I hope that it fixes mu issue.

 

[Ranger44]

That passenger side HO2S is stuck on lean. OR is actually doing it's job but only reading lean. It's worth the shot to replace the HO2S. But you could have a leaking lower intake as they are common on the 4L. OR a lack or fuel delivery on that bank.

I was a little skeptical of the EGR at first, but it's on the drivers side bank IIRC. You could test the EGR and apply full vacuum. It should kill or cause the engine to run rough at idle. It usually cause the truck to buck randomly.

I would really look into codes and let us know. Would help out. Ford EEC-IV is actually pretty advanced for an OBD-I system.

 

[PORTnPOLISH]

That passenger side HO2S is stuck on lean. OR is actually doing it's job but only reading lean. It's worth the shot to replace the HO2S. But you could have a leaking lower intake as they are common on the 4L. OR a lack or fuel delivery on that bank.

I was a little skeptical of the EGR at first, but it's on the drivers side bank IIRC. You could test the EGR and apply full vacuum. It should kill or cause the engine to run rough at idle. It usually cause the truck to buck randomly.

I would really look into codes and let us know. Would help out. Ford EEC-IV is actually pretty advanced for an OBD-I system.

I did check the codes.most of them were from things I was unplugging while trying to diagnose the problem.I did have a code for lean condition right 02 and low voltage right 02 so I hope it works. I checked for intake leaks with carb cleaner all over and found nothing. Of the intakmani was linking wouldn't it get worse with. Wot.

 

[Ranger44]

Leaking intake manifolds sometimes can't be detected with carb cleaner.

It could also only act up during certain situations and rpm ranges.

Just try the HO2S and see what it does. It's worth the try. After that it would be off to looking for a vacuum (don't forget fuel injector O rings can cause a leak too) or exhaust leak before the cat on that passenger side.

Have you insured the injectors are firing on that side? An automotive sethoscope works well for this. You could also ohm them outwith a multimeter. I think 12-16ohms is normal. OL, or anything much higher is usually a bad sign. A noid light can also be used to ensure the injector is receiving a steady signal to fire.

 

[PORTnPOLISH]

I can hear the injector on the number three cylinder firing. And just to be sure why would wot allow it to run okay? It makes sense the at wot when the pcm ingnores sensor values that it would run okay wouldn't it? And if there was a leak pre cat but after the 02 it shouldn't matter. In a rare situation I did have a 02 sensor with a leak after it get affacted by the leak but it was directly after and the rangers is a good distance back from the 02.