Odd stumbling, lack of power, and low fuel mileage problem

[dogboy]

I have searched thoroughly in the past, and did a quick search just now, but didn't see anything new. I know this is a long post, but if you guys could PLEASE help me, I would appreciate it!!!
I hate throwing parts at a problem, but I have been only because I have the spare parts off of the Explorer.

Ever since late October, I have been having an endless issue with my 4.0L... An odd lack of power, and 10-11mpg. I am getting the codes of "bank 1 sensed lean", and "bank 2 sensed rich", as well, and the light will come on and go off at random during a drive.

I did the M5OD swap in it in mid October, but did not swap the computer, I am still running the auto computer, but I don't think that is my problem. It ran JUST fine for about 2 weeks after the swap. And at that 2 week mark, my battery was completely shot (had been bad for a couple months, but met it's last day), yet under Les Schwab's warranty, so after jumping the truck, I took the truck down there. It ran fine for about 5 minutes after leaving their parking lot, then shit hit the fan. It had a COMPLETE lack of power, as in 3500rpm at 45mph, and it would not accelerate, lack. But then as if somebody flipped a switch, "most" of the power would come back, then a 30 seconds later, it would pop back into it's complete lack of power mode again, and would continue to switch back and forth at random. It only did the problem EXACTLY like that (in severity), that one day, after that I just had a constant mild lack of power, but a bad lack under about 2500rpm's. But if I accelerate, once I get to about 2500 it usually snaps out of it, almost like somebody flipped a switch, or bad turbo lag or something.

Me and my auto shop teacher suspected dirty injectors. But I first replaced the IAC valve with one off my parts Explorer due to the rpm's not normally coming below 1000rpm at stop lights, that didn't do anything, and neither did cleaning it. Then I replaced the MAF sensor with the Explorer's, and it ran slightly better, so I cleaned it, and it didn't make a difference. Then I tested the Throttle position sensor, and it tested good. That was all back in December.

Fast forward to last Thursday (yes I dealt with the problem for 2 months without changing anything) I cleaned the injectors with the chemicals and cleaning tools in our auto shop at school (not an in-tank cleaner). At the same time, I realized that the vacuum (it has 21psi of vacuum by the way) line going to the fuel pressure regulator was not connected, just hanging there, so I connected it, REALLY hoping that between the injectors and plugging the regulator back in, that my problem would go away. The regulator sort of made sense as a cause to my problem as well. Too much fuel (bad mileage) and pouring too much fuel down it's throat at low rpms would cause a lack of power, until higher rpm's. No luck.

Then on Saturday, I replaced the O2 sensors with the Explorer ones to see what happened. Replacing the drivers side didn't do much, but the problem almost went away after replacing the passenger's side, only problem was a slight lack of power at all times that was no where near as bad as before, no insta-power/ turbo lag anymore. My teacher had told me that it is wise to replace the plugs after using the injector cleaner, so I thought that might finish it off (plugs were new in early November). But instead of helping the problem, the lack of power, and insta-power problem came back. So I put the old plugs back in, which were gaped at .040", not .054" (why, I don't know...) like the new plugs, but the problem is still there...

So, here's what I have checked, or replaced:
plugs/ wires (tested wires)
injectors
TPS
IAC valve
MAF sensor
Fuel filter
O2 sensors (both)
Air filter
Thermostat (last June)

What would connecting the battery backwards do, would it cause symptoms like these? I am almost thinking that Les Schwab connected the batter backwards and screwed up the computer or something. I'm just baffled by the "intermittent-ness" of the problem, it is not constant. I would think a computer problem would be constant maybe.

Do you guys think that havign the regulator's vacuum unplugged for who knows how long, could have done anything?

It has also been hooked up to the Scope in my shop class as well, and all the plugs were firing like they were supposed to, but the problem really comes out, when you drive it, so I guess they could still somehow be misfiring when on the road, but not at an idle.


Thank you for any help, I will really appreciate it.

 

[cllake]

Check your cats, their probably clogged. Exact thing happened to my brothers fullsize.

 

[dogboy]

Unless gutted cats could have been clogged...

The problem existed when I had the hollowed/ gutted cats (I put them on when I did the tranny swap, and took them off about a month later, and put on real cats) then I put the stock cats back on.

 

[dogboy]

I just remembered that is has acceptable fuel pressure too. About 39-40psi at all times.

Could a fault temp sensor for the gauge do anything like this? I know there are separate sensors for the computer, and the gauge, correct?My gauge has ALWAYS been low, usually hovering over cold mark, and sometimes going to the "N" in normal on the gauge. But like I said, it has always done that for the 2 years I've had the rig.

 

[fireguy12117]

the temp gauge sending unit has a single wire on it near the throttle body. the sensor for the PCM is also near the throttle body, but has a two wire harness plug on it.

there is a possibility (sorry for my ignorance, but it sounds like you swapped a MT in place of an AT?) that the PCM itself is the problem. the AT PCM just has a couple of signals to the tranny for shifting points, BUT (i've not been able to confirm this) there is a possibility that the emissions programming compensates for an AT being in the drive train. the MT could be throwing that off as the PCM is expecting extra lag of weight, or whatever to appear at the motor. i hope someone can speak to that better than me here.

i do know that there are seperate part numbers for auto trans and manual trans PCM's, but in any case, your describing to a T what happened with my truck and it turned out to be a burned out PCM for the MAF. the funny thing was it never threw a code for the MAF, it just ran like crap till i swapped a different PCM then got codes, then had something to work with, but it was still the wrong PCM. i matched the proper part numbers for what i needed, tracked one down, swapped it in, and it was a whole new truck.

 

[dogboy]

I get what mean about the tranny thing, and it was what I was thought at first, but then the whole running right for a couple weeks thing came into play. All the manual computer does is cut fuel to the injectors during engine braking, and also does not control the tranny, and a few other things, or so I've been told. I get a code for 1-2, and 3-4 shift solenoids, and then also one for the torque converter, but that is it.

I think you might be on the right track with the Computer thing. I still think Les Schwab connected the battery backwards or something and screwed the computer.
I need a new computer anyway, so this just makes me do it sooner!
Now the hard part will be finding one, haha. '93 4.0L 5 spd Ranger.... most were automatics.

 

[fireguy12117]

yeah, there is a servo motor for the 1-2 band and similar for the 3-4 band and i think a torque lock up. the pcm isnt seeing those devices, so its thrown the code. i just never knew to what degree the manufacturers programmed the first generation computers.

the intermitten issue does point towards a faulty pcm. intermitten problems downright suck. there are a couple places online, but i ended up getting lucky with someone offering the correct part here on TRS, so get the right part number and start searchin the junk yards and online.

i heard from two sources that fords in particular were suseptable to computer failures in early on, so i take that with a grain of salt, but given my situation, it seemed to fit.

 

[dogboy]

I was talking to my autoshop teacher today (he ran a very successful shop for 25+ years before becoming a teacher 5 years back), and he said that very rarely were the computers at fault, but honestly, I agree with you about it probably being the suspect. We'll see. I am taking it into class tomorrow and were are going to try and narrow it down some more, maybe.




EDIT: Wow, there are 5 different computer possibilities...
(ECU), 6-245 (4.0L), MT, ID F37F-LA
(ECU), 6-245 (4.0L), MT, ID F37F-UA
(ECU), 6-245 (4.0L), MT, ID F37F-UBMR
(ECU), 6-245 (4.0L), MT, ID F37F-UB
(ECU), 6-245 (4.0L), MT, ID F37F-UC


Would anybody be able to point me to which computer I need? Or, what the difference is?
I'm searching for the answer right now, but I am not finding anything.

EDIT2: I have not done a compression test, but could it POSSIBLY have anything do do with a blow head gasket? It doesn't sound like a head gasket to me, but I'm no expert either. I'll do a compression test for the hell of it tomorrow anyway.

 

[mazdamama]

hey, this may sound stupid but try crossing your 02 wires. when i did my transmission i accidentally put my o2 sensors back together crossed because i had to remove my exhaust. i drove like this for six months until it finally occured to me. this problem alone gave me four or five codes, which were intermittent , but consisted of too rich bank 1, and 2, and also too lean bank1, and 2. i took it to my mechanic and they blamed it on the computer as well, and during this time like your truck, my truck was only getting 10 mpg.

 

[fireguy12117]

hey, this may sound stupid but try crossing your 02 wires. when i did my transmission i accidentally put my o2 sensors back together crossed because i had to remove my exhaust. i drove like this for six months until it finally occured to me. this problem alone gave me four or five codes, which were intermittent , but consisted of too rich bank 1, and 2, and also too lean bank1, and 2. i took it to my mechanic and they blamed it on the computer as well, and during this time like your truck, my truck was only getting 10 mpg.

damn the simplest things, wow......ida never guessed that one.

dogboy- this is from memory and doesnt exactly answer your question but i did discover in my case for AT, they had different part numbers for rangers, explorers, and there was also a transition from motors with BAP sensors to MAP sensors, to just having MAF sensors. the BAP and MAP motors both having MAF,s- but i dont remember if they had seperate PCM numbers. sounds cheesy but have you tried just googling the part numbers and seeing what comes up?

 

[dogboy]

I'll have to double check the O2 sensors. I don't "think" they are plugged in backwards, but you never know.


Nah, I haven't really searched the part numbers... I found the number on a wrecking yard price/ parts finding page, and had to go to bed right afterwards...
I thought all Ranger's had MAF sensors. I guess I was wrong! It would make sense that a computer would be different between a MAP sensor, and a MAF sensor.

I'll be doing some more searching tomorrow and over the weekend though.

 

[fireguy12117]

those motors with the BAP and MAP's also had MAF's. it kind of surprised me when i stumbled into it, but i double checked a couple sources for wiring diagram and sure enough there were two sensors around 91, 92ish, and around 93 or so, the gen 3 change, it seems like they went with all MAF's for rangers, but i cant remember for sure on exploders.

 

[dogboy]

Ok. The problem is with the Ranger by the way, not the Explorer, I don't know if I worded that badly or something.

We'll have to see, my Uncle pretty much runs a wrecking yard around me, so if the computer doesn't work, I can probably just take it back.

Pulled the codes AGAIN today, and I got 4 codes, bank 1, lean, and rich, and also bank 2 lean and rich. But what is odd, is I would think that if the problem were a backwards, or disconnected O2 sensor, that the CEL would be on all the time, not intermittently like it is.

I'll probably head to the wrecking yard tomorrow and see if I can find any of the 5 computers... There's a 1/5 chance it will be the right one, but any of them may work,.

 

[fireguy12117]

i was just giving the information out there since i thought the explorers and rangers were identical with the PCM's and they are not. i was looking in explorers for a replacement which ended up not working for me.

the older rangers did have dual sensors (which i think i wasnt too clear on, that it was a MAF and one of the other two). i found a 91 ranger 4.0 but it threw a CEL for the BAP sensor, but the MAF was reading fine.

but anyhow, kinda went off topic for why there are 5 part numbers. another idea was that they had different ones for extended cabs versus standards.

i still dont fully understand why reversing sensors would do that, since it should be an identical sensor...no idea how the CEL would react...

 

[mazdamama]

i
i still dont fully understand why reversing sensors would do that, since it should be an identical sensor...no idea how the CEL would react...

if your refering to the 02 sensors, it triggers a CEL because there is an o2 sensor on each side of the "Y" on the exhaust. one o2 sensor reads the air/ fuel ratio for bank 1 while the other reads the air/fuel ratio for bank 2 of the engine. if you have the wires crossed and plugged into the wrong connectors it will confuse your engines computer. For example if your wires are crossed and your o2 sensor detects a rich condition in bank 1, it will try to solve the problem by leaning out the fuel to bank 2 or vice versa. If it detects a lean condition in bank 2 it will try to fix this problem by dumping more fuel into bank 1. now can you see why this is the exact (and probably only) cause of the Intermittent CEL codes for
too rich bank 1 and 2, ...and
too lean bank 1 and 2