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Surging on hills 1.4T

11K views 17 replies 15 participants last post by  obermd 
#1 ·
I should start out saying I Live in Hilly SW Wisconsin, its rolling hills that are 100-400ft in height. The first couple tanks of gas I used premium & noticed no issues with my car, now with 87octane I notice what can best be described as surging while going up hill. at first I thought I was imagining it, but with my girlfriend driving she looked over at me like WTF is the car doing, so I knew it wasn't just me.

Even on a small slight grade I thought I felt this surging, but on bigger hills when the car downshifts(its an auto) the problem is more pronounced. I read on a few post here the car is pulling timing because it senses knock with the low octane fuel but the way it feels its more like it dials things back for 1sec, then trys to go full power again & keeps cycling between the two until the top of the hill(a nice queasy see-saw feeling).

I have a ScanguageII but have not hooked it up yet to see if it is the computer retarding the timing, I was wondering if anyone else has experienced this? does anyone know what these motors usually run at(stock tune) for timing?

More info:
It has not been that warm here(around 50degrees during the day)
I only use Top Tier Gas(just not premium the last couple fill ups).
 
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#2 ·
A bit more info, the hill we had the issue on was only about 130ft elevation change over a 1/4 mile of so. It was only the steepest part of the hill, which according to this website(below) is a 7% grade.

Also if it matters this was after driving for 5+ hours over hundreds of hills with seemingly no issue at all. This was also the first hill we had seen in 10miles or so, so the engine should not have been warm.

Percent Grade between N42 52.696 W89 36.742 and N42 52.402 W89 36.715 - veloroutes.org
 
#3 ·
I would say you are correct, that it is due to the 87 octane fuel. As the PCM detects knock it will retard the timing until the knock goes away and then start to advance the timing until it knocks again. This is the surge you most likely feel as the PCM retards, advances, retards, advances the timing. I could be wrong, but this is my guess. I have noticed this with my 2012 1LT RS Auto while using 89 octane when the temp was around 83 degrees outside. I plan on using 93 octane the next fill up to see how it performs, since it is only 1.30 more per tank.
 
#5 ·
spacedout,
If you feel that this is an issue, I would suggest that you take your vehicle into your local dealership and have them look into this for you. If you would like I can contact your dealer to set up an appointment for you. Please send me a PM with your name, phone number and VIN if you would like me to do so. Please keep me posted on this issue. If you have any questions please feel free to contact me.
Thank you,
Stacy Chevrolet Customer Service
 
#13 ·
spacedout,
If you feel that this is an issue, I would suggest that you take your vehicle into your local dealership and have them look into this for you.
No thanks, In this day & age it would be a complete waste of time to take the car to the dealer with any issue that doesn't throw a code. No code & I'm 99% sure they will say its by design & can not duplicate.

Post number 3 on this topic is exactly correct. Hooked up my scangaugeII & could see the timing/boost being pulled on hills. switched to premium gas & the issues disappeared.
 
#6 ·
I get the same thing with my 2012 2LT RS 1.4t 6MT running no ethanol 89 and 91. I think it is worse after I have been driving for a while, I have an hour commute each way. Sometimes my car will feel like the power has just. It in half and it will drop 15mph going up some slight grades.


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#7 ·
I had the exact same thing happen in my 2012 LTZ RS Auto. First noticed it on the way home from the dealership going up a significant hill. I assumed it was due to the crappy fuel the dealership filled it with. I couldn't wait to finish that tank. Since then, I've been putting Shell 93 in it and have not noticed it again.
 
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#18 ·
Lisa,

Before installing a Trifecta tune please let us know more about the symptoms you're trying to resolve. If there is an underlying problem that isn't software related an aftermarket tune won't help.
 
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