Engine hesitation while cursing

[AllBlackBimmer]

So this morning it was very cold and snowing... I don't think that is the cause of my issue, but am just noting it.

I get on the highway and am driving slow due to the conditions... about 30-40mph in 2wd.

At this point, I have already been on the road for 10-15 mins and my engine was at normal operating temperature.

Not under heavy load, just cruising along, the truck seemed to sputter and hesitate for just second... it did this 5-10 times on my 10 mile highway drive.

Under heavy load - I.e. pushing the gas pedal threw the floor, there is no issue. At idle and during cold startup, no issue. When accelerating and coasting without pushing the gas pedal no issue.

Only when cruising along at highway speeds did I notice this.

I don't think its a transmission thing...

Engine is 4.0 SOHC.

I know I should probably check the MAF sensor and fuel filter form searching the forums, but does anything have any insight as to what it might be?
Most of the other "hesitation" threads I've seen seem to be under heavy load, or going uphill or towing, or had issues during idle or startup... I didn't experience any of those issues.
I was on pretty much flat ground, cruising, lightly touching the gas pedal.

I will be making an appointment to take it to the garage this afternoon... I just bought this truck and it has a 3 month warranty on it.

 

[RonD]

First, all gasoline has moisture(water) in it and for the most part it is diluted enough to not cause any issues, it can't mix with gas but unless there is alot and it settles to the bottom of the tank(water is heavier than gas) it will just be pumped up and burned with the gasoline in small enough quantities as to not cause an issue.
Cold weather is a little different as the water can freeze and these ice crystals can cause issues, especially in the fuel filter.

Ethanol/methanol added to the fuel will mix with and bond with the water making it less likely to cause an issue, water can't freeze if bonded to ethanol, that's how coolant/anti-freeze works, and that's what products like HEET are for.
But if you are running an ethanol/methanol blend you shouldn't need to add anything else.

I don't think this is your issue, because it would usually show more at higher fuel demands not in the middle.

Yes, MAF sensor could have some issues, bucking and stumbling are known symptoms of MAF problems

Also TPS(throttle position sensor), it could have a bad spot, a worn spot, long shot but easy to test.
TPS gets 5 volts from computer, when throttle is closed .9volts is sent back to computer, when throttle is wide open 4.7volts is sent back to computer.
So the TPS is like a volume control or light dimmer, a variable resistor.

The way the computer saves you money on MPG is that it turns off the fuel injectors when RPMs are above 1,100 and TPS voltage is at .9v, i.e. foot off the gas pedal and you are coasting, it will turn injectors back on to idle engine when RPMs drop below 1,100.
(on a carb engine fuel is continually sucked in even when coasting, it ain't much but it ain't nothing either, lol.)

Say you are cruising along at 1,800rpm.
If there is a dead spot, say near a 1/4 throttle, then computer would see 2volts and then .9v(dead spot), assumes your foot is off the gas pedal so injectors would shut off, engine stumbles your foot moves on pedal and 2volts are back, so stumble and recovery.
Very easy to test TPS with volt or ohm meter.

 

[AllBlackBimmer]

First, all gasoline has moisture(water) in it and for the most part it is diluted enough to not cause any issues, it can't mix with gas but unless there is alot and it settles to the bottom of the tank(water is heavier than gas) it will just be pumped up and burned with the gasoline in small enough quantities as to not cause an issue.
Cold weather is a little different as the water can freeze and these ice crystals can cause issues, especially in the fuel filter.

Ethanol/methanol added to the fuel will mix with and bond with the water making it less likely to cause an issue, water can't freeze if bonded to ethanol, that's how coolant/anti-freeze works, and that's what products like HEET are for.
But if you are running an ethanol/methanol blend you shouldn't need to add anything else.

I don't think this is your issue, because it would usually show more at higher fuel demands not in the middle.

Yes, MAF sensor could have some issues, bucking and stumbling are known symptoms of MAF problems

Also TPS(throttle position sensor), it could have a bad spot, a worn spot, long shot but easy to test.
TPS gets 5 volts from computer, when throttle is closed .9volts is sent back to computer, when throttle is wide open 4.7volts is sent back to computer.
So the TPS is like a volume control or light dimmer, a variable resistor.

The way the computer saves you money on MPG is that it turns off the fuel injectors when RPMs are above 1,100 and TPS voltage is at .9v, i.e. foot off the gas pedal and you are coasting, it will turn injectors back on to idle engine when RPMs drop below 1,100.
(on a carb engine fuel is continually sucked in even when coasting, it ain't much but it ain't nothing either, lol.)

Say you are cruising along at 1,800rpm.
If there is a dead spot, say near a 1/4 throttle, then computer would see 2volts and then .9v(dead spot), assumes your foot is off the gas pedal so injectors would shut off, engine stumbles your foot moves on pedal and 2volts are back, so stumble and recovery.
Very easy to test TPS with volt or ohm meter.

Good post, thank you. Throttle position sensor sounds like something good to check.

What about spark plugs and/or coils? I'm not really sure what a misfire would feel like (As dumb as that sounds) but I would think it would misfire upon heavy load or heavy acceleration... not at cursing speeds.

It's weird because most people with hesitation or sputter problems all have them under heavy load and have signs of rough idle, which I have neither.

When I noticed the hesitations today, I was definitely barely on the throttle with very light pressure.

I also tried to watch my RPM gauge for drops or shaking, and the RPM gauge didn't seem to move or drop when I noticed the hesitation.... would the TPS show any signs that correlate to RPM?

 

[96Indyram]

My 87 ranger with the 2.9 does the same thing.
cruzing speed, light pressure on gas pedal, just enough to maintain speed. And it does the miss/hit/sputter. at 30-40 mph. Give it gas and it does fine, and idles fine.

I figure it is a "dead" spot on the TPS. Being that is the position it is used most of the time... just off idle enough to hold speed limit. anything over 55 mph it does not do it because I am pressing more on the pedal and past the "dead" spot on TPS.

 

[RonD]

If it is the engine that is stumbling then RPM should drop, that's what you are feeling.

But if you have an automatic trans the torque converter could be unlocking then locking again.

 

[scotts90ranger]

yes the rpm should be moving but most tach's are so filtered that you won't notice it and the wheels are attached to the engine so while moving it's hard to tell, it would be more noticeable with a vacuum gauge but they're usually orifice'd so they're filtered as well, my Ranger has a bit of a hesitation at 55 as well that is similar to this, idle vacuum is within about 2"Hg of normal, but has kind of a dead spot at 55 where it takes more throttle than normal to get there, and runs normal when you push the throttle a little further to the power enrichment area which I'm guessing is around 75% where it kicks in and the turbo goes to it's normal boost pressure. My guess is a metered air leak of some form on my end...

 

[AllBlackBimmer]

Now what is puzzling is, when I left work yesterday... no issue... when I drove into work today... no issue.

I am at a loss as to what it could have been? Yesterday before I noticed it I was using 4x4, but put it back in 2wd before getting on the highway, I highly doubt that is of any relevance and had anything to do with it.
Maybe it was a bad gas or somehow water got where it shouldn't have? I am going to drive another day or two and see if it does it again. It was even colder this morning - in the teens, and will be single digits this evening/tomorrow morning, so I don't think the cold had anything to do with it either?

 

[Mickey Bitsko]

I'm having similar issues with my 4.0 ohv... this post was dead in january 2015,
did you ever find the problem ? sell the the truck? or did the problem just go away?

thank you for response

 

[Andy D]

I would suspect that you picked up a load of bad gas and now you filled it up with good gas?.

 

[Mickey Bitsko]

Same old story, pulling a small grade in 4th [auto] started missing a little , shifted into OD and backed out of the throttle cruised fine 2400rpm no hesitation, first thought change fuel filter, could barely blow through it, before installing new filter turned key on several times till fresh clean gas flowed. put new filter on ran nice for 25 miles and started bucking again, might have crap in the pump pick up filter. I know ANYTHING is possible.
There are numerous posts on here that address a similar problem, and it seems when the OP finds/fixes the problem they drop the ball and don't post the fix/problem.
Enough of my rant...lol I would imagine it could be any number of things, I'll keep tinkering and IF I find it's that is something that a barely BY mech can fix I'll FINNISH my post,
Any other suggestions would be appreciated

Also, changing gas stations, the one that is the cheapest IS the CHEAPEST GAS for a reason, so no more of that junk !

 

[Andy D]

Try a bottle of Regane fuel system cleaner. use as directed

 

[Mickey Bitsko]

Thanks Andy D I'll try a bottle today and keep you posted..

 

[Mickey Bitsko]

Our local NAPA doesn't carry Regane, the veteran counter help [an older fella]
Told me the gas in this area is pretty bad at bet and guys have been having good luck with Sea foam gas additive, so far so good, must be water thats giving people problems.
Runs as good as ever...