I was on vacation and driving my 09 GTS (with only 8,000 miles on it) along a four lane highway in South Carolina. It was a warm day and I had four people in the car.

I was cruising along at about 65 mph and decided to push it up to around 85 mph to make better time to our destination and to impress my nephew with the awesome torque and acceleration of my GTS. So, I decided to drop her down to 5th gear with my paddles. When I did this, instead of the car picking up torque and pushing harder, it seemed like the engine or the transmission could not handle the lower gear. The RPM's did not spike really, it was just like the gears started to slip on me or something. Then I noticed that the check engine light had come on, but I'm not sure when it came on (before, during or after).

THen yesterday I was driving home from S.C. and the car was behaving the same way. It continued to exhibit a sluggishness. I was on a two lane highway and decided to try to pass a car in front of me that was only going about 50 mph. So I just stepped harder on the accelerator to see what she would do. No dice, man. It just would not accelerate fast enough to accomplish the passing. Then, as I was cruising down the highway at about 70 mph it seemed like the transmission did not like being in 6th gear and it was like it was trying to downshift but didn't really downshift .... it would kind of hesitate and chug a little bit.

Then, I stopped at a gas station to fill it up. I turned off the ignition and gassed it up. WHen I started her up, it kind of hesitated and chugged a little bit like the pistons were misfiring. Geeze.

Needless to say I have to bring it to the dealer. I was just wondering if anybody had any ideas of what might be going on.

p.s.
one weird thing that i am remembering is that on the trip down to S.C. I stopped and some old dude filled up my car at a full service gas station. as I was leaving the station he said "make sure you come back here and fill up on your way home because our gas is better ... it doesn't have any ethanol in it." is it possible that putting ethanol-free gas in the car was a mistake?

 

maybe he filled you up with 85 or something. seems like the exact situation that i had when i had to fill up my carrera with 85 b/c we were out of 93oct in houston awhile back b/c of the hurricane. it seems like the electronic knock control system was kicking in.

 

with the CEL on, your car has gone into "safe mode" where it trys to limit any damage by not giving you access to full power or revs.
you need to hook her up on a diagnostic machine and read the code that has triggered the CEL
then get it fixed asap.
it could be down to bad fuel or something more serious

check it now......
good luck.

 

that is very helpful. it is probably in safe mode. I am going to call the dealer tomorrow morning. my guess is that it would be best to have it towed rather than driving it 25 miles to the dealer. do you agree?

 

if its because of "detonation" it would definatly be wise to get it towed
If the car is "knocking" it can damage pistons/valves etc. and cause your cat's to fail
and on such a new/expensive car i would be inclined to tow her.

better safe than sorry.
sounds like all you need is the tank emptying and flushing through
then the CEL light resetting.
the system on your car only records a fault when it occurs more than 20 times (so as not to record every fluctuation or simple glitch) so they will know excatly what has caused this.
might be that your MAF or crank case position sensor has failed? (doubt it though)
im going with fuel.

good luck anyway.

 

that happened to my cayenne but it happened as i accelerated out of the gas station so i had to get it drained then towed to a different gas station to get it filled with 93octane

 

slightly off topic.

what grades do you have in the USA?
here we have
diesel
unleaded 95
unleaded 97
and at some petrol stations you can get unleaded 99 (ron)

all UK cars are tuned to run/accept 95 (ron) but obviously prefer 97+
we also use an octaine booster such as millers to "aid" performance.

what is this "low" grade petrol for???
sounds nasty.

 

US ratings are slightly different. We use the average of research and motor octane - (R+M)/2. 87 is regular, 89 is mid-grade and 92-93 is premium (east coast US/sea level).

As far as the "low" grade petrol, I've gone 9.70s in the 1/4 on my bike using 87 octane.

 

i didnt mean it like that Wayne.
i ment what is this "low" grade stuff that people have wrongly put in there cars that have made them run badly?

we can put the "lowest" grade here in our cayennes) (95 ron) and they run fine

but if you guys put your lowest grade in they run badly...so what is this low stuff aimed at?
sounds like chainsaw material

i do know that when my friend imported an american dodge he had to have it retuned to better run on our fuel?

 

I find the auto tranny to be in the wrong gear once in a while on my 09 CS. This weekend there was an incident where there was a half second pause followed by a abrupt jerk and a loud bang. I was not driving aggressively, it took place after decelerating towards a stop and accelerate again without coming to a complete stop. Has anyone experienced this?

 

wow we've gone really pc when were worrying about non ethanol'd gas being detrimental......

 

Your 95 RON is equivalent to our 91-92 (r+m)/2.

It has nothing to do with quality, but rather the octane necessary to keep the engine from detonating. Lots of cars run well on our 87, which would be around 91 RON. The benefit is that 87 is much cheaper, so most economy cars use 87.

Once you get into performance cars or more highly "tuned" engines (like the Cayenne), you generally have to run premium. That would be your 95-98 RON and our 91-94.

 

Yes, I've experienced this too. It's like the tranny get confused.

 

im with you now.

i dont think there is a car in the uk that would run on your 87 (91 ron)
no wonder the cayennes that have missfuled are experiancing problems
i didnt know there was fuel as low as a 91 ron
you learn something new every day.
thanks for putting me right.

 

Wikipedia says that Russia has as low as 80 ron available.