Bucking

[Matthew preen]

Hi

I have a 2004 explorer I'm experiencing bucking at around 45 55 mph but only when overdrive is on and if I'm going 60 its fine or I gotta let off the gas and it stops then starts again if I'm into the gas again around those speeds. Also my 4x4 high light blinks 10x every couple minutes anyone got any idea would be great

 

[IIGood]

Is it bucking as you're accelerating through those speeds or if you're going steady at that speed, it bucks?

I had a bucking issue with my '03 XLT 4x4 when I first got it nearly 2 years ago. There were two different tires on it...the fronts were BFGs, the rears were Firestones. Even though they were all the same size, the fronts were more worn than the rears and as such, there was about a half an inch difference in the overall diameter between the fronts and rears. So I'd guess the system was trying to account for that and would produce the "bucking" as I accelerated. If it got REALLY bad, then the tire pressures were low.

Once I put a new set of tires all around, I had no more bucking. So check that first...what are your tires like? Are the pressures even all around? Are all 4 tires the same?

 

[Matthew preen]

Yeah its when I'm accelerating if I let off the gas it stops and my tires are all the same but my rears are more worn then the fronts and both left tires keep loosing air slowly so that very well might be it never really thought it could be from something like that. Any ideas on the 4x4 light blinking ten times every couple min thought maybe the speed sensors?

 

[IIGood]

I'm not entirely certain on the 4x4 light blinking...I've looked that up here as well since my 4x4 LOW light blinks if I hit that. If I recall correctly it's related to sensors in the transmission or the solenoid...I don't quite remember. You can do a search on this forum for it and there were several threads about it, or create a separate thread just for that. I honestly don't think the two are entirely related, but I could be wrong.

But, I would get fresh tires if they're due.

 

[Drewmcg]

Is yours the 4.0 SOHC or the 4.6L? How many miles? How well maintained?

In that speed range, the O/D tries to engage at relatively low RPMs in the corresponding gear (4th?--not sure). If the engine has lower-than-normal torque, due, e.g., to a need for a tune-up (spark plugs; wires; air/fuel filter; cleaning of throttle body/MAF sensor, etc.), then the PCM might think there's more torque available than there actually is.

Maybe try this quick experiment (a little bit spendy): Next time your tank nears empty, try filling up with Premium or Mid-Grade, instead of 87 Octane. If the bucking stops, then you can conclude its from the higher power at that same RPM range. Look to do a tune-up. If not, well, that's probably not your problem.

It might also be worthwhile to re-set the memory in your PCM. Since youtube video by FordTechMakuloco or posts on this forum on how to do that. Good luck.

 

[apenland01]

This is fairly common with these explorers with tires being different, more specifically, newer tires on the rear and worn tires on the front. Since that is how tire shops install new tires, it can cause problems. Also, if you have mismatched brands, even if they are the same size, since tire size is ratios, not exact measurement.

If the "smaller" worn tire is on the front, the sensors detect faster rotation of the front tire as slippage and tries to correct by kicking in 4x4. Most people describe bucking or lurching when this happens, especially at moderate speed when the wheel revolutions are fast enough to trigger a correction.

There could be some other issues, but if you don't have all 4 tires matching exactly, I would start with that, especially since you are getting the 4x4 light as well.

 

[MrPulldown]

I was driving down the highway a couple weeks ago, and we hit this section of road way that they were fixing. Weird pavement. Looked like it was temporary. Very poorly paved and was already worn. Kind of a mix between whoops and washboard. The Exp bounce around a bit but then started to buck. I had dropped my speed down to 55mph already but the bucking was almost violent. My wife even noticed. I was fearing that it could have been a transfer case failing, and we were just about to start a 500 mile road trip.

After that incident it never did it again. I contribute it to the road causing the wheels to turn at slightly different speeds as one was lifted and other set compresses, then confusing the auto 4wd, advance trac...

The Ford seems very sensitive to its auto 4wd engagement. One of our other cars a RAV4, has an auto 4wd and it is seemless. You never feel it thunk into 4.

 

[Drewmcg]

I was getting a slight bucking around 45 mph on my 2x '02 4.0 SOHC XLS before I got my timing straightened out (which would go away if I turned off the OD). So its not just a four-wheel drive thing--though the OP's problem could be.