Highway Surging/Pulsing

EFLine · February 9, 2017

So I know we all have the shakes when it comes to our trucks, but I have been experiencing a new "feature".

I'll be driving down the highway around between 65-80mph depending on highway and traffic and get a surging or pulsing feeling. It almost feels like the transmission is slipping, or it's knocking itself in and out of overdrive. The RPMs do not jump and it's not when it shifts from V4 to V8.

Does not seem to matter if cruise is set or not, and will happen multiple times, sometimes consistently every 45 seconds (rough numbers). Just trying to say it's not a one time deal while I'm driving.

Any ideas?

BigBadSierra · February 9, 2017

The first thing I would do is disconnect the battery let it sit for 10 minutes and then drive it again for a week and see if it comes back.

The last 6 GM's I have had ran on this LANBUS system and they all need a disconnect ever once and a while to start behaving again.

IF it comes back then you most likely are having an issue.

EFLine · February 9, 2017

Thanks BBS. funny you mentioned that. I had to do that last week because MyLink crapped out on me and disconnecting the battery, (along with the fuse) was a supposed "reset" for it. Might not hurt to attempt it again though to see what happens.

rcl · February 9, 2017

Each time I had this problem I discovered a spark plug wire disconnected. First was the No. 1 cyl. Second was the No. 5. Not sure why they keep coming off the plug. Anyone else have this issue?

EFLine · February 9, 2017

Each time I had this problem I discovered a spark plug wire disconnected. First was the No. 1 cyl. Second was the No. 5. Not sure why they keep coming off the plug. Anyone else have this issue?

Interesting, i'll go to the garage and check that out. You would think that this would throw a code, did you happen to notice if yours had a code or not for like a cylinder misfire?

15_silverado · February 9, 2017

EFLine what year, engine and trans do you have?

The spark plug wire problem is common; I think there was a hole thread on that, and maybe even a TSB....I see if I can find it. There's a metal clip inside the boot of the spark plug wire where it connects to the spark plug, that metal clip becomes loose or even falls out, then the spark plug wire will not stay on the spark plug. If you have this problem you are supposed to replace the spark plug wire.

The surging is a separate problem I believe, especially depending on what year your truck is. There's been other posts/complaints about this. Apparently for the 2016-17 GM knows about this and is working on a reprogramming solution. The engineers said the trans needs more slip to be smooth but the trans engineer says more slip may cause damage to the transmission. (This info comes from another member who works at a dealer, I'll see if I can find that tread)

rcl · February 9, 2017

No codes. The engine light went on and off intermittently which might be related to the clip on the spark plug wire bouncing on and off of the plug. When I got home I plugged my code tester in and it gave me a 0305 code, (don't quote me on the code number, going from memory last night), and stated "cylinder 5 misfiring". It's easy to find just give the wire a little tug and you'll see it's just disconnected. I stopped at the GMC service dept today, told them about my two incidents and they said they had not heard of any issues with this. If you find that thread or TSB Bob I'd be interested in seeing that. Thx

15_silverado · February 9, 2017

No codes. The engine light went on and off intermittently which might be related to the clip on the spark plug wire bouncing on and off of the plug. When I got home I plugged my code tester in and it gave me a 0305 code, (don't quote me on the code number, going from memory last night), and stated "cylinder 5 misfiring". It's easy to find just give the wire a little tug and you'll see it's just disconnected. I stopped at the GMC service dept today, told them about my two incidents and they said they had not heard of any issues with this. If you find that thread or TSB Bob I'd be interested in seeing that. Thx

Spark plug wires

http://www.gm-trucks.com/forums/topic/193036-loose-spark-plug-wire-heres-the-fix/

http://www.gm-trucks.com/forums/topic/175878-spark-plug-wires-coming-off/

Edited February 9, 2017 by 15_silverado

15_silverado · February 9, 2017

Spark plug

http://sandyblogs.com/techlink/?p=6827

PIP5159A: Engine Misfire May Be Due To Spark Plug Wires

Google. PIP5159A

Edited February 9, 2017 by 15_silverado

15_silverado · February 9, 2017

Surging

#PIP5457B - Surge hesitation Chuggle Misfire Feeling With A Light Tip In

Google. PIP5457B

Read through this...Read what "Quank" says

http://www.gm-trucks.com/forums/topic/197058-fuel-pump-comes-on-when-i-open-door/page-1

15_silverado · February 9, 2017

Spark plug wire issue looks like it's on the coil end. But I would check both ends, maybe same problem.

Darth_Vader · February 11, 2017

Turn off the traction control and see if it still does it, report back.

EFLine · February 16, 2017

Hey guys, been out of the country and love all the great info and will read through this tonight. I really appreciate the links!

I will follow up with what I find.

Will have to investigate a tad more but it MIGHT be a pulsing or surging with V4 mode (AFM) that I didn't think was the case before... but coming back from the airport I watched it super close with the pulsing / surging and seemed to possibly correlate to when AFM kicked in.

whistleblower · July 6, 2021

Realize I'm bumping an old thread but I just purchased a used Yukon XL with the 6.2L and 62k miles and 10 speed transmission. I noticed this 'pulsing' when driving it 7 hours back home on the highway 70-80mph. This is my first time driving the 6.2L. Did you ever find a fix for your issue? Is this a common problem? As the OP mentioned, feels like the transmission is slipping...