Surging sensation at freeway speed

[JPaul]

Been meaning to ask about this for a while. Has anyone else had an issue when driving up a steep hill at freeway speed (60 mph or faster) where you can feel a rhythmic surging? I want to say it feels like the front axle loading and unloading or something. It only does it if I'm driving up a steep grade at high speeds, but as soon as I let off the gas or the grade evens out it goes away.

My center diff bushing looks fine, so I'm not sure what it could really be. It's not really bad surging either, just noticeable.

 

[GreatDaneHummer]

Have you tried the basics like cleaning your throttle body, checking your spark plugs or running some injector cleaner through? Mine usually starts acting up when the throttle body is covered in oil looking like crap.

 

[JPaul]

I ran a can of sea foam through the intake before my trip to Moab this last weekend and still felt it. The plugs should be pretty new (provided the dealership that replaced my engine listened to me and swapped the plugs over). And I cleaned the TB early last year. It's been doing this pretty much the whole time.

 

[Jack_M]

I had something like that happen on my BMW came to find out the boot was torn between the intake manifold and the throttle body. Have you checked the intake manifold to see if it was loose? Just a thought to try and help out!

 

[K0PIR]

Been meaning to ask about this for a while. Has anyone else had an issue when driving up a steep hill at freeway speed (60 mph or faster) where you can feel a rhythmic surging? I want to say it feels like the front axle loading and unloading or something. It only does it if I'm driving up a steep grade at high speeds, but as soon as I let off the gas or the grade evens out it goes away.

My center diff bushing looks fine, so I'm not sure what it could really be. It's not really bad surging either, just noticeable.

I have something similar going on. It feels more like the transmission surging and not the engine running poorly. Does yours?

My front diff bushing is worn and I wonder if that's it. I'll replace it this summer. I don't think the passenger even notices it, but I'm aware of it.

 

[humvee]

Same here, Its pulses continuously when driving. Sounds muffled.
Should really go under and change some bushings bushings.
Hope its not your trannys, good luck and keep us posted when you find out.

 

[JPaul]

Yeah, I'm not sure what it could be. Bushings were a thought but I've checked mine and surprisingly the front different bushing is in great shape. Probably helps that whoever owned it before me never took it off road.

Sent from my SM-N910T using Tapatalk

 

[JPaul]

I've run some Sea Foam spray through the intake and now I'm running both a bottle of Techron and a bottle of Sea Foam in the gas tank since I'm also getting a stumble at idle every now and then, and driving home from Moab I picked up a temporary P0303 when I was accelerating up the onramp to I-70.

I'm planning on also replacing the coil packs, the truck is almost to 100K miles and they are probably starting to wear out.

 

[scoreh3]

When mine did that , I swapped coil packs and plugs . Problem solved ! I also cleaned the t/b and mas air flow sensor too.

 

[alrock]

Curious if you'd get this same surging on level ground (or even downhill) with high RPM. What about taking a stretch of road in 3rd gear just to get RPMs higher. My first thought would point to MAF sensor or an air leak in intake, as mentioned before. When you cleaned the throttle body, did you remove it or clean it in place? If it was removed, was the gasket replaced? Check bolts on the intake manifold and make sure they are tight.

 

[JPaul]

I think it's always done it, not just after I cleaned the TB. When I cleaned it I fully removed it, I think. It's been a while since I did that. It only does it going up steeper grades on the highway, I haven't noticed it on level ground even when accelerating heavily. Could be air leaks in the intake. I have been thinking about pulling the intake completely and replacing seals and doing a thorough cleaning of it, as well as pulling the valve cover off and giving it a good scrub. But after my ordeal with my snorkel, I'm saving that for a later date...