My 1992 Ranger 3.0 V6 stalls sometimes and throws lean codes on both banks. It goes away for weeks at a time then comes back and makes it almost not able to drive. MAF replaced, new plugs and wires, belt, waterpump, timing cover gaskets. Tested fuel pressure, and no vaccume leaks, tested o2 sensors. Throttlebody looked clean when I took off the vaccume line from the MAF. Havent taken off the IAC might replace that. It started doing this a month ago for about a week, then went away after I started using Cheveron instead of the **** gas station. I put 92 octane in and didnt have problems for weeks. Just last night though after driving on the freeway home, I pulled in my lot, parked for 2 minutes, started it up to leave again and it stalled when leaving the lot twice, took a while to start each time. I could hear the fuel pump him like usual, but when it wouldnt start I would hear the hum and it wouldnt stop. When it does work, I hear the hum for 2 seconds when the key is on. Its stalling again today and had to leave it at my friends. I need help with any suggestions!

 

Checked fuel pressure. Koeo it's 40, running its 32.
New fuel filter. Still stalling when it wants to. Went all day yesterday no stalling now it's stalling bad in the worst places.

 

Welcome to the forum

Sorry I missed this when first posted

1992 3.0l Ranger will use a distributor and TFI module spark system
These were an issue when they got older, the module would cause issues after it warmed up, causing stalling and no starts

Good read here on that: Ford EEC-IV/TFI-IV Electronic Engine Control Troubleshooting

Worth testing or replacing module.

Lean codes means there was too much Oxygen in the exhaust, when a cylinder misfires then NO Oxygen was burned so it is dumped into the exhaust where O2 sensors "see" it and you get Lean codes.
So your Lean codes could be result of spark misfires not a fuel issue.

Your Fuel pressure looks right where it is suppose to be

 

Ok I will read about the module. It misfired on my way home now and I let it idle in the driveway and it died. I can't get it started back up.

 

I have no idea where do find the module on the truck. Gonna have to check the book.

 

It is on the side of the distributor

 

I see it on our 86 ranger but on the 92 its harder to see but I looked around the distributor and dont see it. So yesterday it was stalling very bad at my friends. We idled it a long time and it stayed misfiring and stalling once in a while. Drive it around the block misfiring and stalled 3 times in reverse. Then after running it longer we drove for like 2 hours straight no problems at all. This is very confusing because it started misfiring again and stalled in the driveway this morning. Then ran it almost half an hour and started to not misfire anymore but I had to leave it at my friends to go to work.

Could the distributor module be causing it do be like this? Also what do I call it when I go to O'Rileys for the part?

Could a bad computer (PCM) be causing this problem to come and go?

Ran great no problems for about 2 weeks no misfire codes, comes back, goes away when ran for an hour yesterday, guessing itll randomly go away for a while again. Racking my mind over what it could be since Ive checked so much.

 

Oh, you could have remote mounted TFI.

Look on rad support

Look for something like this: http://www.therangerstation.com/tech...emote_tfi1.jpg

 

Ok I'll look when I get off of work, thanks. How could this module be giving me intermittent problems that come and go? I still can't find this part of autozones website or O'Rileys. Might have to call them since I don't know how to word the part.

Also, any other ideas on what it can be?

Edit: just read about the tfi problems. From what I read this would cause problems when warming up. As of right now it's running better when it's running hotter and all warmed up compared to the warming up process. But that's for now at least. I did have trouble starting a few times now

 

Now all Im getting are these codes from my Ford ODB-1

10
411
538
536


No 02 sensors reading lean during my last several tests over the week.

Checked plug #1 and #3 for their gaps and were both spot on and looked good.. checked mainly because cylinder #1 threw the 10 code indicating something going wrong there like a misfire

 

Got back from work, let it warm up, before I took off it jerked and missed when I looked at the engine, drove fine up the road and around the corner then the CEL came on and off. Almost back home it comes on but goes away when I restart the car. Then drive 2 hours straight with my friend NO PROBLEMS. Now it's like when it's warmed up and driven it'll be ok...

Oh I found the ICM you were talking about. It's right next to my radiator. It's a motor craft, haven't taken it off yet to really look at it. But it wouldn't come stock with a motor craft one would it?

 

yes, Motorcraft is Ford's Brand, like AC Delco and GM

There are no "0"s in OBD1, codes need to be pulsed and you can't pulse a "0", so 1 thru 9 only

So not sure where 10 came from, 1992 to 1994 Rangers should use 3 digit codes.........should doesn't mean does, lol
Ford played pretty fast and loose when they change computer OBD1 software from 2 to 3 digital codes, so while 1992 "should be" 3 digit, it could still have 2 digit software.

So HOW are you reading these codes?

411 = Idle speed system not controlling idle properly (generally idle too high)

536 = Brake On Off open or shorted to ground

538 = System did not receive "goose" test <<< ignore

My thoughts on the TFI system were because you have gone thru Fuel system and still have the problem........so maybe problem is spark related, or wiring in the spark system, between distributor and remote mounted TFI module
25 year old wires can get brittle and/or frayed

 

My book says 10,20,30 ect refer to the corresponding plugs. 10 being spark plug 1.

Drove all day without a single misfire or stall. This is driving me nuts.

Codes were done KOER
KOEO it's just passing or picking up cylinder #1

 

Again, what device are you using to read the OBD-1 Codes?

If you are using a hand held scanner then you need to run the cylinder balance test for those misfire codes to be valid, they are not stored in memory they are only used during active test, so are not OBD1 codes themselves, OBD1 codes do not have "0"s
Test procedure here: EEC-IV Testing - Cylinder Balance Test

 

It's an innova ford odb1 reader 1981-1995.
Not sure how to start the balance test.

 

Then ignore the 10 code, it shouldn't be in memory and maybe you inadvertently started the test and then ended without knowing.

And code 538 with code 10 would prove that out

Instructions for doing the KOEO and KOER test: http://www.corral.net/tech/maintenan...-koeokoer.html

You do the balance test after these two tests and BEFORE shutting off the engine, that test is in my previous post.

Balance test would have nothing to do with why engine is stalling out, all it is doing is seeing if each cylinder is adding the same amount of power to the crank when it fires, similar to an electronic compression test

 

Ok I'll do that but I think it'll pass... now that it's been running great no stalls for the past 3 days. I don't get how it'll mess up bad 2 days then all of the sudden get better. I drove for 2 hours straight each night and no misfires or stalling.

 

Any connection to outside temp, night is usually cooler temp than day time?

 

Ron!

After I did my radiator swap yesterday and drove it, and again today, I ended up with a CEL tonight. 159 is new I havent gotten that one before. (other ones are in this order 10,159,173,538,536) Ran good when I unplugged the MAF cord and drove it around the block even. Now that I let it cool down it doesnt run good with it off. Gonna disconnect terminals and reset it and see what codes come up again tomorrow.

Ideas?

 

Ignore 10, 536 and 538 they are test codes

Codes are listed here: OBD-I Diagnostic Trouble Code (DTC) Applications - Ford 3-Digit Codes

You should look up and post what each code means so we don't have to look them up as well.
i.e.
159 (O,R) MAF sensor is/was out of range - MAF
173 (R,M) Oxygen sensor not switching - system is or was rich - Single, Right or Rear HO2S - Fuel control

If you unplugged the MAF sensor then you would get 159
If you think code was stored prior to unplugging MAF then check MAF wiring and voltage.
As described here: Ford Ranger Mass Air Flow Cleaning, Removal and Installation

173 means the passenger side(right) upstream O2 sensor has high voltage(.9v) and computer reduced the fuel on the right side but O2 sensor still showed .9v, it wasn't "switching" to a lower voltage.
O2 sensors generate their own voltage, .1 to .9volt
O2 sensors react with Oxygen in the exhaust, not gasoline
High oxygen levels reduce voltage, .1, that is said to be "Lean"
Low oxygen levels increase voltage, .9, that is said to be "Rich"

Check the wiring on the passenger side O2 sensor, follow wires up to its connector and check there as well.
Each O2 sensor also has a heater, it gets 12volts when key is on, if wires get shorted then computer could get above .9volt and no switching, so check wires carefully.

Codes are ok but don't really help as much as just looking around at what is happening with the engine.
There no computers ever used in a vehicle to run the engine, we call it that but it is not like the computer or even smartphone you are used to thinking of as a computer.
Vehicles use a larger number calculator to calculate air/fuel mix, based on pre-programmed tables(formulas) and off set by "sensors".
There is no "thinking" done.
And like all calculators if you enter the wrong number then the final result will be off, garbage in = garbage out

So do NOT expect a code to tell you what is wrong with a vehicle, it can't.
"Then what good are they?"

Not much really, they are there to help mechanics narrow down possible "sensor" failure which causes the calculator to be off.
It doesn't take the place of looking at the engine.
Is vacuum low?
Is there black smoke from exhaust, Rich?
What do spark plug tips look like?

 

PLugs look good to myself and my mentor.There wasnt any black smoke before but now Im noticing a little bit. Its very thin so its hard to see but I think its sort of black maybe. Im supposed to get a voltage meter today to check these things again. Is it bad to drive with the MAF unplugged?

Also the 159 came up with it plugged in.

When i brought my truck to firestone months ago with the stalling problem they said it MIGHT be the PCM and wanted to change it. They had no other ideas. I asked if they checked the o2 sensors and they said they did but I think they were lying.

Also my book doesnt state which sensor is having a fault. Just says HO2S sensor fault basically

Had my vacc tested and everything was fine

Runs like **** from a cold start with the MAF unplugged but once warmed up its drivable. Could this mean the o2 sensor is bad and is also throwing the MAF code? Because the MAF was replaced before I bought it and it looks great.

 

Im wondering if the MAF uses the o2 sensors to create the mixture, and if the MAF is unplugged if its still reading the o2 sensors or not.

Had the o2 sensor codes before and Im wondering if its actually just the o2 sensors.

So does the MAF use the o2 sensors while plugged in and not plugged in?

Trying to rule things out. I might go buy an o2 sensor today instead of waiting to order if the MAF does NOT use the o2 sensor while UNPLUGGED

 

Engine computers(calculators, lol), have two main operating methods
Open Loop and Closed Loop

Open Loop means computer has no feedback from some sensors, so it will run Factory air/fuel mix tables until it does have feedback.

An O2 sensor can't work until it is heated up, minimum temp is 600degF, so very hot which is why they are "heated", to get them working ASAP.
Under 600degF it can't read oxygen levels in exhaust accurately.

So main purpose for Open Loop is so cold engine can be started and driven until O2 sensors warm up.
If you unplug the MAF sensor or TPS or other main sensors the computer will also switch to Open Loop, because it has lost feedback.

Closed Loop means engine is warmed up, O2 sensors specifically, and computer is now running the engine based on MAF sensor, TPS and O2 sensor data.
Best MPG happens in Closed Loop since computer is adjusting air/fuel based on feedback.

There is no connection between MAF and O2 sensors
The MAF is a heated wire sensor, air flow passed the wire cools it down, how much it cools down tells computer how much and how "heavy" the air is.
MAF sensor sends computer between 0 and 5 volts, the lower the voltage the lower the air flow, so you might see .6volts at idle and above 3.5volts at 3,500rpm coming out of MAF going to computer.
Computer also "knows"(was programmed for) it's engine size, so your computer "knows" that at WOT(wide open throttle) this 3 LITER engine will suck in 3 LITERS of air ever 2 RPM(4-strokes)
Computer also "knows" how much a LITER of air weighs, at sea level.
And computer "knows" how much a gallon of gasoline weighs.
air:fuel ratio for gasoline engine is 14.7:1, this is a WEIGHT RATIO

this is why 200mpg carbs or "pre-vaporizers" were/are BS, lol.

The MAF sensors function is to offset this "knowledge" that the computer has about the weight of the air coming in, at 2,000ft above sea level the air is lighter
When outside temp is 40deg the air is heavier than at 80deg, hot air rises, because it is lighter than cooler air

So the MAF sensor there to fine tune "known" air weights

O2 sensors use a chemical reaction to generate voltage, like car batteries do.
So O2 sensors DO wear out, just like batteries do.
Life expectancy for O2 sensors is 100,000 miles, but Rich running(high voltage) over time can shorten their lives, uses up chemicals faster
.1 volt from O2 mean high oxygen
.9 volt means low oxygen

Computer, in Closed Loop, adds fuel to the engine via fuel injectors
As said it "knows" how much gasoline weighs
It also "knows" how much Fuel Pressure there should be, and the size of the injectors
So, for example, if computer open a fuel injector for 100milliseconds it knows .1gram of fuel will come out of that injector.
(Not accurate numbers just easier to understand)

Computer calculates 14.7grams of air is coming in so it will open injectors to add 1 gram of gasoline to that air to get the 14.7:1 ratio
And it does this on the fly, which is why this computer is basically just a large number calculator.

Anyway, after the computer has added that 1 gram of fuel, it gets the O2 sensor data, feedback, if O2 voltage is .7 (rich) then computer shortens the Open time on the injectors by a few milliseconds
If O2 voltage is .2 (lean) then computer lengthens the open time for the injectors by a few milliseconds
Sweet spot for computer is to keep O2 sensor voltage between .40 and .45

This all happens in milliseconds, O2 sensors react very fast as does computers open time for injectors.
Computer also has to run engine Rich and then Lean to keep Catalytic converters working
Cat converters need to stay hot to work, Rich exhaust keeps them hot so computer is programmed to do that.

If you have a V6 engine then you will have a Passenger side and Drivers side O2 sensor, some just had the one
173 (R,M) Oxygen sensor not switching - system is or was rich - Single, Right or Rear HO2S - Fuel control

This means that the computer was in Closed Loop, and was shortening the injector open time, but O2 sensor was not showing less than .8/.9 volt, not "switching" to lower voltage as computer Lowered the fuel
Computer has upper and lower limits based on RPM and throttle position for the fuel injectors, when you reach one of those limits computer will set a code like 173

Yes could be O2 sensor is worn out
Could be fuel injector is leaking fuel into intake
Could be Fuel Pressure regulator is leaking fuel into intake, via vacuum hose

And yes, could be Computer has a problem

 

Ok now the exhaust isn't looking dark anymore. Looks "normal". Im gonna clean the MAF right now and see if theres any change but I doubt there will be since it looks very clean.

o2 sensors and MAF's are almost half the price of retail on Amazon. Would it be worth getting a new MAF and o2 sensor to try resolving the problem?

 

Just cleaned the MAF and put it back on, still doing the same thing. Ordered an o2 sensor for the front, its old and rusty so its gonna be frustrating to get off.
Was driving with the MAF unplugged about 4 miles like I did earlier but it stalled twice while using the gas. Hitting the gas would do nothing but one time it kicked back in while doing it. After the other stall it took a few times to get it to weakly turn over. Made it back home without stalling though.

So what Im getting from your answer is "With the MAF unplugged, the engine wont be using the o2 sensors" since its in open loop???

Gonna try the new o2 sensor anyway before I order another MAF since it looks new and is clean. It makes me wonder if its the MAF itself or something that disengages when the MAF is unplugged. Thats why Im asking if the o2 sensor is affected by the MAF being unplugged/plugged in.

Thanks for all your help by the way RonD I appreciate this.