98 2.8L 5V.

A couple years back I was told by an indie shop that I could clear codes by disconnecting the battery for about 30 minutes, then reconnect with the ignition switch in the on position. I did it once and it worked. I did this again today and now the car will not idle normally, in fact it slows so far it dies.

This happened once before when I replaced the battery - I think the dealer told me I had to have them reset the ECU.

Can I fix this myself or is it off to the dealer or shop? I do not have a VagCom or any code reading device.

Thanks

 

Well, you said it happened before, but I'm just guessing here.
You may have an issue that's unrelated to the battery disconnection. While I worked on and off for several months on my '95 2.8 12v, I had the battery disconnected for weeks at a time. I never experienced anything like you're describing.

When was the last time when you changed the fuel filter?
Maybe it just happens that the Idle Control Valve may go sour on you?

 

Do not reconnect the batt with the key in the 'on' position. You are setting yourself up for damaging power surges as there is now a much greater load. If you get a big enough one (you'll see/hear it spark when reconnecting), or even a small one over 50v or so, you can take out things in the ECU and/or other controllers.

Whats the codes you tried to clear and what do you have now?

 

I suspect you need to go through a throttle body calibration. I don't know about the 98, but the cars with electronic throttle body automatically calibrate themselves once the battery is disconnected. You just have to disconnect the battery, turn the iginition to ON postion without starting the car, and wait a few minutes for the throttle body to go through the calibration.

 

One could think that there's no relationship between the TB and idling.
I thought at idle the throttle body is closed.
Isn't the Idle Control Valve responsible for opening up and allowing air to bypass the throttle plate and keep a steady RPM?

 

You mean reconnect the battery then turn the car to 'ON', right...?

 

This worked. Thanks

 

With electronic throttle body, there will not be a separate idle air control valve. ECU controls idle speed by changing the throttle valve opening angle

 

Well, I don't have knowledge of what year Audi model has what type of throttle body. It would in my opinion be (to a larger extent) a waste of time to load your memory with tons of info concerning a vehicle that you don't have. I doubt anyone is different in this regard, unless is a savant in which case probably doesn't drive at all.

I was giving my perspective, as I have a C4 with throttle cable AND an ICV. In this case, the butterfly flap at idle is CLOSED.
thanks.

 

Yes, 1998 A6 or A4 with engine code AHA or ATQ does have throttle valve control module (drive by wire, no separate idle control valve)