Surging at highway speed

[Mabags]

2020 with 3.6 and auto trans, 30,000 miles. Recently on a trip it started surging at highway speed, felt like it was either trans going in and out of gear or engine losing power. Wife said from passenger seat it felt like I was pumping the brakes. It goes in to get checked next week, prepared for dealer to tell me they can't reproduce the problem. Was wondering if anyone else had a similar issue and what was the fix.

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[GOCAMPN]

By chance did you witness anything funny in the RPMs? Possibly air intake or fuel filter.

 

[Medical_Bartender]

I had a similar issue years ago in my manual JK and it was associated with the AC compressor cycling on and off. You could tell by the RPM fluctuation.

 

[Jeepin' John]

I think mine (2 times) was less-than-great 87 gas. Pulled over, shut off, waited, cranked, back on the highway and same cyclical surging. Filled up with premium BP at next stop and ran normal instantly. Same thing happened a few months after and realized i filled up at a "random" station. Better gas cured it again. I now run only Shell, BP, or Exxon 87 and it hasn't come back for me.

 

[Mabags]

By chance did you witness anything funny in the RPMs? Possibly air intake or fuel filter.

Rpms seemed to hold steady

 

[Mabags]

I think mine (2 times) was less-than-great 87 gas. Pulled over, shut off, waited, cranked, back on the highway and same cyclical surging. Filled up with premium BP at next stop and ran normal instantly. Same thing happened a few months after and realized i filled up at a "random" station. Better gas cured it again. I now run only Shell, BP, or Exxon 87 and it hasn't come back for me.

Bad gas was one of my guesses, I had just filled up at a marathon that I use all the time and never had a problem with

 

[Jeepin' John]

Bad gas was one of my guesses, I had just filled up at a marathon that I use all the time and never had a problem with

You're kidding - i know the first time it happened to me it was on a marathon tank. So weird

 

[ShadowsPapa]

I had a similar issue years ago in my manual JK and it was associated with the AC compressor cycling on and off. You could tell by the RPM fluctuation.

Holy crap! That engine was what, 2hp, to feel the AC make it surge from the seat??

 

[Medical_Bartender]

Holy crap! That engine was what, 2hp, to feel the AC make it surge from the seat??

hahaha. Just a regular old 3.6 pentastar. With the manual tranny it was only noticeable in 1st & 2nd gear. Putting around parking lots made it look like I was a total newb at stick shifts because of the surge. So bad that I would turn off the AC compressor when I was in a low speed/gear situation - no issues then.

but ended up going on An off-road ride with some people out in Arizona and it was a very bumpy ride. When I got back to the Interstate after that it was smooth as silk with no surging with the AC on. Really weird scenario and I’m still not sure what happened.

 

[Zilla]

2020 with 3.6 and auto trans, 30,000 miles. Recently on a trip it started surging at highway speed, felt like it was either trans going in and out of gear or engine losing power. Wife said from passenger seat it felt like I was pumping the brakes. It goes in to get checked next week, prepared for dealer to tell me they can't reproduce the problem. Was wondering if anyone else had a similar issue and what was the fix.

Sounds like a fuel issue to me. Fill up with good, high octane gas, and a bottle of STP gas treatment....I think you'll see a difference.

 

[ShadowsPapa]

hahaha. Just a regular old 3.6 pentastar. With the manual tranny it was only noticeable in 1st & 2nd gear. Putting around parking lots made it look like I was a total newb at stick shifts because of the surge. So bad that I would turn off the AC compressor when I was in a low speed/gear situation - no issues then.

but ended up going on An off-road ride with some people out in Arizona and it was a very bumpy ride. When I got back to the Interstate after that it was smooth as silk with no surging with the AC on. Really weird scenario and I’m still not sure what happened.

That is weird - mine runs AC almost all the time since I leave it in auto mode for the HVAC. I know when it's on due to a slightly different idle sound, but when driving it, can't really tell when the AC kicks on or off. A manual won't absorb the changes like an automatic could, though - but you'd think once an automatic was in lockup, it might feel it as well.

Sounds like a fuel issue to me. Fill up with good, high octane gas, and a bottle of STP gas treatment....I think you'll see a difference.

High octane won't change how it runs - it will simply avoid detonation if there is even any to begin with and detonation doesn't cause surging like this.

Top tier gas of any octane 87 minimum will be just as good.
Octane isn't quality. No more power, doesn't burn more dirty or more clean, no more BTUs.
Any good top tier fuel is going to be clean with the additives the cheap stuff doesn't have, even at 87.

 

[Mr._Bill]

I only fuel up at Sam's Club or Costco, unless I'm traveling, and then I look for one close to where I'm at. Costco advertises their fuel as a top tier detergent gasoline. I started adding Seafoam monthly, last March, don't know if it really helps any.

Sea Foam IC5 Fuel Injector Cleaner, 5.25 oz https://a.co/d/2jjvgGq

I do get an occasional rough idle, but never any surging or other issues. My A/C is on all the time, year round.

 

[ShadowsPapa]

I only fuel up at Sam's Club or Costco, unless I'm traveling, and then I look for one close to where I'm at. Costco advertises their fuel as a top tier detergent gasoline. I started adding Seafoam monthly, last March, don't know if it really helps any.

Sea Foam IC5 Fuel Injector Cleaner, 5.25 oz https://a.co/d/2jjvgGq

I do get an occasional rough idle, but never any surging or other issues. My A/C is on all the time, year round.

Costco is top tier, as is QuickTrip, Mobil and a list of others.

I use mostly Casey's gas, QT now and then. Casey's isn't top tier but it's never given us any issues in decades of using it.

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