engine stumble

[Red89]

My 91 4.0 is somewhat consistently stumbling as i accelerate. If i'm really easy on the throttle it seems to be okay and when i'm maintaining speed its fine. But in the first couple gears if i'm on the throttle much it basically just cuts out intermittently.

The fuel pump is only a couple years old. I think its electrical but I could be totally wrong. I'm going to put new plugs and wires in it today cause they're due anyway, but i'm worried its the whole electrical ignition module.

Any advice?

thanks,

Mark

 

[AaronC47]

Stumbling 4.0

If it only seems to do it when your standing on it and its really needing fuel, But does not do it if your easy on the throttle, I would check your fuel filter, Drivers side inside the frame about under your feet if you were sitting in truck,

 

[xgenralxleex01x]

mine is doing the oposite if im easy on the throtle it bogs down and sluggish but if i gun it it runs better, i sit at a light and it jumps, if im driving down the road i can hear like it has air in the gas line

 

[moto-Leo]

My 4.0 Stumbles when I get on it. I replaced the complete fuel system.
My kid keeps saying it is the maf. I have not tried to change it yet so I dont know.

 

[Red89]

not the fuel filter - checked codes

I replace the fuel filter hoping that would solve the issue. Weird thing is it acted normally for a day or two and now has reverted back to the same cutting out. I had a mechanic pull the codes and I got a bunch related to the MAF. 26, 22, 56, 66.

So I'm going to clean that out and see what happens. Does the MAF sensor just go out sometimes?

Any ideas what else I should check?

Thanks!

Mark

btw - I swapped in a 91 explorer 4.0 motor in my 89 in 2003 with the help of this forum, and this is the first time I've had issues. Not bad huh?

 

[sovok66]

Hi ya I was having the same problem as you after replacing a stuck open thermostat.
I tried everything. Finally i let truck cool off unpluged engine temp sensor started engine ran for a few mins then turn off and pluged it back in and all seems fine now revs great now. ill keep track and let you know how long this lasts

 

[daniel3507]

The MAF can get dirty over time and cause a bad reading. When I took mine off to clean i noticed how nasty it was and it made a noticeable difference after i cleaned it. Might check o2 sensor as well if that doesnt fix it.

 

[powerranger262]

Is there a certain o2 sensor that usually goes first? I want to start replacing them, but don't want to do them all at once. Also, do they cause a CEL when bad?

 

[Yellowsplash]

If your O2 sensors were bad they would pop a DTC. You can easily test them by probing the wires of the sensor and finding the output wire. With the vehicle at full operating temperature, it should oscillate between .2 and .8 volts repeatedly.

For the OP, all those codes relate to the VAF/MAF. If you’re running a 4.0, which has a MAF, clean the MAF first with CRC's MAF cleaner (Don’t use other harsh cleaners as it will kill it). If that doesn’t do the trick, your looking at a new MAF.

 

[Kalwren]

Does the MAF sensor just go out sometimes?

Yes, it can. A good way to test if its going bad, is to just unplug it. Drive it around and see if the stumble goes away. If it does, it's likely a bad MAF.

Check my thread here:
http://www.therangerstation.com/forums/showthread.php?t=73391