97 ranger

[Damnyankee]

So,
I'm looking at a 97 ranger that won't pass emisions.
OBD2 says that its too lean (4 banger).
O2 sensor Looks good (ya, i know that doesn't mean a whole lot)

no vaccum leakes, i went over every line, there arent really that many.

wierd thing,
I pull the plug on the MAF and there is no change in how it runs.
it runs the same with or without MAF connected.

Before we spend the money... am i right that it shouldn't run with the MAF disconnected, every other rig i've worked on won't run.. But i've never worked on one of these ford 4 bangers.

Helpfull advice is appreciated.

 

[Bodaciouscj7]

If I remember right this truck has a 2 piece manifold and could have a vacuum leak where the halves join together. Dealt with that on a few ranger 3.0 and 4.0 v-6's.

 

[zukkev]

Now that its been moved to the appropriate forum....
Do you have access to a scantool that will give you live data for MAF gms/second (minimum 120)??? Or BARO Hertz (minimum 157)??? MAF Volts (Minimum 3.8V, should reach 4.0V; under high rpm accel~meaning 5Krpm!)??? Is there any other code besides the P0171 lean code??? Yes, the OBDII rigs will run with the MAF disconnected...did you pay close attention to how it runs with it disconnected? It may be a very subtle change...Also, take the MAF off and look down the little hole at the two hot wires---are they dark in color, and fuzzy-looking??? If so---pick up some MAF cleaner at the local parts store, and spray those resistors til they come clean; carefully blow it dry...reinstall the MAF and take it for a run after clearing the code, then report back on how it runs...

 

[Fordzuki]

I've moved cars around the shop with no maf. Some are more touchy than others. If you want, I have a scanner that does live data, and the engine in the LJ is a 97, so if you want to play the "swap parts till it runs" game, let me know. :redneck:

 

[comanchekid]

Pull the MAF and look at the the little wires and see if they are dirty if so then clean them with some carb clean but be careful they are kinda fragile.

Dirty MAF sensor is a big issue with Furds....

 

[Damnyankee]

Now that its been moved to the appropriate forum....
Do you have access to a scantool that will give you live data for MAF gms/second (minimum 120)??? Or BARO Hertz (minimum 157)??? MAF Volts (Minimum 3.8V, should reach 4.0V; under high rpm accel~meaning 5Krpm!)??? Is there any other code besides the P0171 lean code??? Yes, the OBDII rigs will run with the MAF disconnected...did you pay close attention to how it runs with it disconnected? It may be a very subtle change...Also, take the MAF off and look down the little hole at the two hot wires---are they dark in color, and fuzzy-looking??? If so---pick up some MAF cleaner at the local parts store, and spray those resistors til they come clean; carefully blow it dry...reinstall the MAF and take it for a run after clearing the code, then report back on how it runs...

no, i don't hae access to a scantool.
There are no other codes.
Maf was sparkinging clean. (but i'll give it another look)

I brought the thing up to about 3k rpms, and unplugged the maf and there was no change, I couldn't tell at idle, thats why i did this test.

normaly it they will at least stumble, this is what had me confused.

I thought i hearda vaccum leak up near the intake but for the life of me, couldn't find it. I'll have another look.

 

[Damnyankee]

darn thing runs fine.

sometimes it will act like its loading up if it idles too long, and the PCV is fine.

 

[traildemon]

Get a can of carb cleaner and spray short bursts around where you think it may have vacuum leaks if there is a leak the carb cleaner will change your idle a little when you get close to the leak thats how I usually find em :awesomework:

 

[zukkev]

Get a can of carb cleaner and spray short bursts around where you think it may have vacuum leaks if there is a leak the carb cleaner will change your idle a little when you get close to the leak thats how I usually find em :awesomework:

:yikes: Use a spray bottle with water; you'll hear the water get sucked in if there's a vacuum leak...if you have spark leak from a plug wire under the intake and use carb clean----POOF!!! No more worries about how it's running!!!:haha:

 

[traildemon]

:yikes: Use a spray bottle with water; you'll hear the water get sucked in if there's a vacuum leak...if you have spark leak from a plug wire under the intake and use carb clean----POOF!!! No more worries about how it's running!!!:haha:

:flipoff: I guess it would be pretty easy to locate loose spark plug wires that way too thanks Kev now I have one more use for carb cleaner :awesomework: I have done this alot thats why I said short burst the thing isnt going to explode :eeek: water wont get up under **** and make your idle change unless its a pressure washer :redneck:

 

[Dogboy]

My 93 4.0l ranger runs no differet with the MAF diconnected, as it does connected.

I almost made that carb cleaner/ leaking spark mistake. I was aiming the can down, and starting to push the button when I noticed spark coming from the plug wire end.

 

[ChopTop84]

Many OBD2 vehicles have three operating modes. Open Loop, Closed Loop, and Limp mode.

Typically, when you first start the rig cold, its in open loop mode. Certain sensors need to get to a certain temp before the computer accepts input from them. O2 sensors usually, as they need to be about 600 degrees to operate right. This is why newer cars use heated O2 sensors, so the computer starts getting readings sooner. While in open loop mode, the computer just runs based on known, or assumed parameters and ignores some sensors.

Once the rig is warm, the computer should switch to closed loop mode. Now the computer accepts inputs and begins actively making changes to the way fuel and spark are delivered.

Limp mode is when a critical sensor has gone completely stupid, or the computer has decided that certain readings dont match expected inputs (sensor out of range high or low). This is really common with automatic transmissions, as the computer is looking at engine RPM, input shaft speed, and output shaft speed, and if the three speeds dont match within a certain range, the computer will throw a fit and may go into limp mode, which limits power, and shifts like crap, but it gets you off the road!

Unplugging the MAF sensor while the engine is still in OPEN loop mode, or in limp mode from another problem, and the computer may just ignore it and run on assumed parameters. It will monitor intake air temp, and barometer, and make a guess as to the amount of air coming in is, not entirely unlike speed density systems of old.

If the only code your getting is for LEAN, and no other codes about sensors out of range high or low, then I would starting trying to find that vacuum leak.

If you run out of ideas, I have an AutoEnginuity scanner with the enhanced pack for Fords, so I can monitor real time sensors, and do KOEO and KOER tests and can also watch the O2 waveform that the computer is looking at. With the waveform monitor, you could start hosing the intake with something and watch the o2 sensor go lean or rich in real time.