I have a 99 Audi A6 Quattro 2.8L.

About a week ago, my brother took the car and filled it up with regular gas because he didn't know it required premium. The next day, I was driving it, and I realized that the acceleration is much weaker than it used to be. When I came to a red light and stopped, the whole display that shows the letters [P RND123] was highlighted. I noticed that this was unusual because usually, only the "D" would be highlighted if I am in drive (which I was). I released the brakes and pressed the gas slowly (as usual), and the car would barely move. The car wouldn't start to accelerate regularly until I pressed the gas pedal to about halfway. I turned the car off and turned it back on, and it worked much better, although I wouldn't say that the acceleration was 100 percent.

A few days later, the same thing happened again. Today, this happened twice. It seems like this problem is occurring more and more often. The car's acceleration does not seem to be nearly as good as it was before it was filled up with regular gas (which is probably expected, but I feel like the difference should not be this great). I literally have to press the gas halfway or more in order to get a decent amount of acceleration.

Despite topping the car off with premium gas in order to dilute the regular gas a few times, this problem is still persisting.

Does anyone know what I must do in order to remedy this situation?

Thanks in advance to everyone!

 

It is not the gas problem. I would say it is related to the transmission. Anyways, get your car scanned. Since it maybe tranny related issue, you may need to use VAGcom or VW/Audi specific scan tool.

 

I use regular gas in my 2.8 all the time without a problem so I don't think the problem is related to the gas as hxgaser says. I also suspect it is the transmission but suggest you get it scanned and clear any codes before making any decisions.

I carry my VAGCom cable in my car just for fun. You would be amazed how many Audi people are driving around with a check engine light on that are afraid to take the vehicle to a dealer because they are scared about how much it will cost. In 50% of the cases I do a reset and the CEL goes out because it was an intermitent problem. Some times the light returns in a few days but many times it dosen't.

PS I always give the guy the codes incase he has another problem.

 

I hear that this could mean that my transmission is in "safe mode".

Can anyone clarify what this means or what it might cost me?

Thank you!

 

It might mean you need some fluid added to your transmission, which won't cost much (relatively speaking, it WILL cost a lot for adding transmission fluid) or it could mean you need a new transmission, which will cost a lot.

Good luck,

Bob

 

Yes, I think the fact that all the figures on the dashboard transmission display are highlighted means you are in "safe" mode, commonly called limp mode. This would be the reason for the lack of power.

I think the possible reasons are that either (a) the engine trying to protect itself from damage, or (b)one or more sensors have failed, and so the engine is running on pre-programmed values, as a kind of "plan B".

As already mentioned, you will need to check for codes with a diagnostic tool. But unless I've missed something, I don't think there's any reason to assume it's a transmission problem.

Disclaimer: I'm no expert.

 

Most definately a trans problem.

BTW, your car has knock sensors. These will detect the pinging caused by lower grade gasoline and retard ignition timing. Power will be reduced, but no damage will occur. The lack of power requires you to push down on the pedal more, using more fuel. This is why it is cost effective to run premium (or at least no worse than going through more regular) It all evens out!

 

You can bring it in to any auto store and have it scanned for free but it will not be a thorough scan and will not reveal all of the Audi fault codes. But it's a start.

You really need to have it scanned at a Audi/VW repair shop or the stealership. If it is low on fluid your doing more and more damage by driving it. Open the window in the morning while it's cold and listen to it is it whining?

You might want to catch the flu tomorrow and get it to a mechanic before you do more damage. It's only costs about 5,000 to rebuild so don't mess around. You may want to bring your brothers credit card with you.

The lower octane fuel would only add carbon to the heads which would take years of running it on low octane. It's not that.

 

It means your brother drove the car too hard... look at the tires to see if they've been burned

 

I took it to the mechanic and it did indeed need more transmission fluid, so we added a bit.

But the problem persists. The mechanic told me that the transmission is also slipping, and it will cost between $1,000 and $2,000 to fix. He says that he has to open up some parts and find out what exactly is wrong with the trans.
I originally bought it for about 5. Is the car worth fixing or should I sell? 110,000 miles on the car.