f350 5.4l stalling problem

[Scott65]

Mass airflow sensor can cause stalling, but unlikely to have set the oss code. Very unlikely. To clean it, pull the plastic shell that clamps to the air cleaner assembly, take the hose off, unplug the connector. Set the housing on a work surface. Pull the rubber boot out where the wires go in, be careful as it won't come very far. Reach in with a flat screwdriver to press in the tab of the lock on the plug, allowing you to pull the harness out. Now you can pry the 4 tabs that lock the center of the housing in, allowing it to slide out of the shell. You'll see 2 tamper proof torx screws (have the dots in the middle). This is the mass airflow sensor. Spray it good from all angles with carb cleaner, shake it out, reassemble. Don't scrub or apply compressed air directly, you can knock the wires loose.

Not sure your environment. I live in a very dusty area, I see this all the time. They get a wad of dirt stuck to them and causes all sorts of problems. Random misfires, running rich or lean, stalling. If the computer doesn't know how much air it's getting, it doesn't know how much fuel to inject.

The coolant temp, as stated, can affect it too. The computer regulates fuel curve based on engine temp. That's why most diagnostics must be done on a warm engine. And many electronic driveability issues don't occur until closed loop (operating temp) operation

 

[sld]

Good idea on the mass air sensor. Just be careful when spraying it. Think of misting it with dedicated mass air flow sensor cleaner. Don't blast it. It is a very very fine wire.

Auto parts store carry the cleaner for this. As usual, disconnect the battery for a reset.

 

[chrisdvorak]

I have looked into the MAF sensor I have not yet cleaned it however I have taken the ducting apart and throughly inspected the sensor and it literally looks brand new. if I unplug the sensor the engine hesitates at acceleration so i think it's operating properly.

 

[sld]

I have looked into the MAF sensor I have not yet cleaned it however I have taken the ducting apart and throughly inspected the sensor and it literally looks brand new. if I unplug the sensor the engine hesitates at acceleration so i think it's operating properly.

That could be but cleaning it is pretty much free and very easy. At least to rule it out.

Is the low idle the only issue? At speed, there are no problems?

 

[chrisdvorak]

yes it is only at idle and now usually only with load at idle like backing up slight hill. it runs and shifts great at any rpm accept idle.

 

[deerefan]

You may have done this, did you clean the throttle body? The mod motors can get a lot of carbon build up in them causing idling and low rpm issues.

 

[sld]

yes it is only at idle and now usually only with load at idle like backing up slight hill. it runs and shifts great at any rpm accept idle.

If it were mine I would definitely adjust the hard stop for the throttle plate like I mentioned earlier. After cleaning the mass air meter and the throttle body.

YMMV though.

Did you take the IAC off and clean it good too?

 

[94BULLITT]

The best thing to do is take it into a shop and get it fixed intead of throwing parts at it.

 

[3930dave]

The best thing to do is take it into a shop and get it fixed intead of throwing parts at it.

Agreed - my first preference is an accurate diagnosis, out of the gate.

That said, unfortunately, finding a shop that A) charges reasonable rates/hours, B) does quality work, and C) is honest is getting to be less likely than finding a mint condition split-window 'Vette for $8k.

Personally, I can make a $/cents argument for occasionally taking a flyer on relatively low-cost parts tossing. I can do that, and still come out ahead in the $100/hr, jam the customer 3 hours on a 40 minute task game.

All that said, once all the basic intake cleaning/checks are done, it may take an OBD scanner that can read live-data to track down a flaky sensor, etc. Those start at about $300 Canadian here.

Rgds, D.

 

[3930dave]

there is 116k on the truck fuel filter was changed about 10k ago the fuel pump is original as far as I know, but I don't think its a fuel supply issue as you can put the pedal to the floor and it will take off at 3k rpm with no problem. this is the first i've heard of the coolant temp sensor could you elaborate?

Ditto what Scott65 said about ECT sensor.

Have a look at how your truck does its fuel pressure regulation (ie. is there still a mechanical fuel pressure regulator on the rail ?). Can't say for sure that your's has it, but at some point Ford started running a variable-speed fuel pump. I don't have one myself, so I haven't learned the quirks of diagnosing those yet - but that control-loop change has stuck in my mind as a potential curve ball, When Things Act Funny. If your truck measures fuel pressure, that is good scan data to watch live, or just measure it mechanically if you can do it safely.

It sounds like you have fuel at high rpm. Reverse, up a hill, is a high-load, low rpm situation - There's a clue there, but I can't say for sure what the answer is..... part of why I'm still thinking fuel though....

Not gonna pretend this is a fix, but throw a bottle of fuel injector cleaner in (Ex. Seafoam), if you haven't recently.

To Bullit's point, if the engine has not been scanned recently by a pro-level scan tool, drop by a Mom'n Pop garage with cash in hand (you don't need a bill) and see if they can pull up any driveability related codes. Some won't set the Engine light.

Rgds, D.