Stalling While Driving/no start

[shr3dd3r 09]

Last week I posted about my truck dying randomly while driving and/or hesitating and losing power. I cleaned every electrical connector I could find and when I tried to start it again I could never get it running.

Tonight I had a final thought...I unplugged the MAF sensor and boom....After cranking for a bit it fired up and ran for several minutes. I then shut her down and plugged the MAF back in and no start. Unplugged MAF....fired right up.

So I assume either the sensor itself or the wires are faulty. What I am uncertain of is whether my stalling problem while driving was caused by this....or if the no start condition began because I sprayed contact cleaner on all the connectors and maybe fouled the MAF somehow....

So, even though this sounds obvious.....do you guys REALLY think the MAF is bad? I know it can cause a no start, but can it also cause random stalling while driving independent from engine load? No check engine light, either.

Also when it was running it was smoking pretty heavily....would this be a result of running rich with the MAF unplugged?

The only reason I ask is because at this point I have replaced literally every sensor that has to do with engine management except the MAF...and I am very very frustrated....

 

[RonD]

Always clean and test before replacing

http://www.therangerstation.com/tech_library/CleanMAF.html
"With the engine running at idle, use a Volt meter to verify there is at least 10.5 volts between terminals A and B of the MAF sensor connector. This indicates the power input to the sensor is correct. Then, measure the voltage between MAF sensor connector terminals C and D. If the reading is approximately 0.34-1.96 volts, the sensor is functioning properly."

I use sewing pins to pierce the wires to test voltage

If input voltage is not correct then you could have a computer issue or wiring.

Yes without MAF engine will run rich as default fuel/air mix is being used.

Not sure it would cause a stall while driving.
Hesitating and losing power could for sure be a symptom of MAF issue

 

[shr3dd3r 09]

Replaced the MAF. No go. It will start without the MAF plugged in and run, but with it plugged in it will not start at all. Anything else I should check? I could not test the MAF with the engine running because it will not run with it plugged in. With the key on engine off I could tell the MAF was getting 12V supply.

I'm at a loss. Nearly every electronic sensor that has to do with engine management is brand new. The only electronic things left are the computer and the wiring harness itself. Unless there is some easy fix I haven't thought of, this thing is going to become my paperweight....well I guess it already is.

Is there any reason why it would not even start with the MAF plugged in, even though the MAF is brand new? Shorting something out somewhere in the MAF circuit? As soon as I unplug it it fires right up but runs way too rich.

 

[RonD]

B and C on the MAF connection should be grounds.
C is the ground thru the ECU I would test that ground.

What kind OBD II codes have you gotten, does the CEL(check engine light) come on when the key is first turned on, and then go off and come back on when engine starts, with MAF disconnected CEL should come on when engine starts.

Have you reset the computer, unhooked battery for 5 min.?

 

[shr3dd3r 09]

No codes. That is what has been weird about this whole thing.
CEL comes on a few minutes after the MAF is unplugged if I let it run.
CEL does light up when I turn the key but goes off after it starts, as is normal.
I have reset the computer.

Haven't checked the "C" ground yet.

 

[HAPPY+RANGER+GUY]

?? tough cookie

Is it possible we bent or pushed a pin somewhere when all the connectors were taken apart for cleaning?

The truck was running fairly well before we broke all those connections apart.

Are you sure all the connections are fully back together, sometimes they could appear to be together but in actuality not fully seated and locked.

 

[HAPPY+RANGER+GUY]

replacement parts

Here's another thought...are you sure all these replacement parts are the correct parts for your truck? This includes the MAF you bought of course.

Any other past electrical issues you've had with the truck that may be related to what's going on now?? For example wiring that was damaged and repaired previously....anything else.

 

[shr3dd3r 09]

All the parts are correct. I made sure of that. I'd be ashamed of myself for buying the wrong electric parts as an electrical engineer haha.

The only other issue I had on this scale was literally the same issue. Except it happened 3 months ago. It would stall while driving/occaisionally lose power and then lurch, as if it were starving for fuel or the mass air flow was bad...

I checked fuel pump voltage, fuel pressure, inertia switch, cam sensor circuit, crank sensor circuit, mass air, etc. All good. So I started replacing things. New fuel pump, cam sensor, crank sensor, and many others.....

None of these fixed the problem. Then one day, literally as a last ditch effort I replaced the canister purge valve and solenoid and as a result I instantly gained power and the problem completely went away. But now it is back...

I have no clue why the purge valve would cause this problem, so it may have been sheer coincidence that the problem went away at the same time.

The computer has an SCT chip in it that killed all the auto trans functions, and the egr line has been removed and tuned out, but aside from that there are literally no mods to anything else. Stock 5.0L mountaineer motor, M5ODR2 tranny from F-150, BW4406 transfer case, and original mountaineer wiring harness.

The pinouts for all the large connectors were identical to the ranger's so everything mated right up. Unused pins controlled signals that went to the message center on the mountaineer, but nothing special. At one point I reinforced the PCM ground because there were exposed wires.

The whole time I had this problem it never threw any codes that seemed relevant. I had a code for running rich, but one day at a stoplight it started idling rough and the CEL turned off and the truck started running fine again and I have not had that code since. That's all I can think of....

I'm still at aloss as to why it will start only with the MAF unplugged. There has to be something in that circuit that has failed, or it's the computer and by starting it with the maf unplugged it defaults to limp mode.

 

[shr3dd3r 09]

On that note does anyone have a pinout for the MAF sensor and circuit? Including grounds and inputs to the PCM? I'd like to go through every connection and troubleshoot.

 

[HAPPY+RANGER+GUY]

nitty gritty

Looks like that solenoid and the MAF get power off the same lines...which originate at the PCM Power Relay. I would start looking at that PCM power relay and all the associated wiring to the MAF, fuel pump relay, etc....a lot of these share common feed and maybe something is bringing it down.

There is also a power diode or two in that power circuit.

 

[HAPPY+RANGER+GUY]

....go through every connection and troubleshoot.

Since we're looking for a needle in haystack....I was told by a friend that those fusible links can go intermittent and cause some crazy issues sometimes. This circuit may have a fusible link involved with it but you'd have to verify that.

 

[HAPPY+RANGER+GUY]

correct tool for the job

Scotty says get your hammer out to find the problem!!

https://www.youtube.com/watch?v=zwlruD4JXmY


Maybe watching this will click a light bulb with you...LOL

.

 

[shr3dd3r 09]

Haha! Trust me I would certainly like to take a hammer to it at this point.

The only thing I know is it starts without the MAF plugged in, and when I plug the MAF back in it will start running rough after a few seconds and die and won't start again until I unplug the MAF again. And the MAF is new....

So it must be something in the MAF circuit. Wiring, PCM, power distribution, etc. The leads on my multimeter gave out on me so I need to grab some new ones to troubleshoot some more. Need to check the resistance between the MAF connector and the computer/power distribution box/battery terminals.

In the meantime maybe I'll visit Scotty's site and ask him haha!

 

[shr3dd3r 09]

Okay, so all of the MAF pins have good connection to the PCM, power, ground, etc. However, the signal return wire shows 4.82 K-Ohms between it and battery ground, and it also shows resistance in the Mega-Ohm range between it and the PCM ground... It's the GY/RD wire on the MAF connector.

There are all kinds of sensors spliced into the signal return wire, which feeds into the PCM on pin 91 or 92 if I remember right. Is the signal return supposed to be grounded? It is the signal return for the intake air temperature sensor in the MAF...

That is the only fishy connection I could find so maybe it's my problem.

 

[RonD]

If there are 4 wires on the MAF then there is no air temp sensor, it will be on the intake.
6 wires means it also has air temp sensor with the MAF sensor.

Yes the grey and the grey/red wires are for the air temp.