I drive a 99 A4 2.8 Quattro 5 speed with about 85000 miles on it, I had my timing belt replaced as well as a couple other things around 77000, recently after having after market stereo and subs installed with capacitor the car the car will idle normal for a bit then the rpms will drop to around 800 to 600, when this happens my battery voltage will go down to around 12 volts from 14 and at times lower then 12 killing my car. when I am driving the rpms will bounce around at idle but causing the issue with the voltage but when I accelerate everything goes back to normal until I come to a stop and idle again. I disconnected the wiring from my battery for my subs to see if that was possibly the problem and it went back to normal for about a week, now again the rpms will drop at idle and the battery will lose volts. It only happens after driving the car for around 15 to 20 minutes, short trips all but 1 time have been fine. I have had a few people say that it sounds like the alternator is bad, I had my batter tested and it tested fine. I don't know much about cars so I am taking the car in to have the alternator tested and possibly replaced, but I was wondering if anyone knew anything about this problem and could let me know if I am wrong for getting the alternator looked at. I also have a problem when i drive my accelerator will stick causing my car to be stuck at whatever rpm and speed I am at, it will become unstuck if I slam on the gas, but happens continuously after that. Tonight I was driving and this problem caused my rpms to get stuck at around 4000 and I could not get them to go back down without downshifting but right after i downshifted and then re-accelerated they would go back to 4000 steady, I had to ride my clutch and downshift constantly to get the car to my destination. When I would push in the clutch my rpm would go up around 5400 rpm and stay there. It stopped after I shut the car off and let it sit for a little while, but this was the worst of a reoccurring problem. Any ideas on this as well?

 

Dude that is the alternator

 

Thanks man, I really don't know much about cars, so I appreciate the answer.

 

i would be more concerned of that gas pedal/acceleration problem you have than the alternator.

 

The mechanic I normally have do my work said that could be because my throttle body could be gunked up, and it only really happens when it gets really cold, tonight was -20

 

All I have to say is, VAG-COM IS YOUR FRIEND....run some diagnostics with it....VAG-COM software gives you more codes/options/info than any other scan tool for an Audi....just food for thought.....

It's a great investment.

Could be cable sticking..could be electronic....difficult to say....

 

I'll look into it, thank you!

 

Anyone have any ideas as to why my accelerator sticks? Last night after driving a short distance my car was idling at about 3200 rpm, it took about 10 minutes to go down, after it went down the rpm dropped to under 1000 and almost caused the car to die. I shut the car off before it could die on me.

 

Look up the procedure for cleaning your throttle body, doing a throttle body alignment, and doing a vacuum system seafoam treatment. If it's a crud issue those are likely to fix it.