I have been lurking for a while. And I have learned quite a bit from this site.

I finally had to register in order to ask a question. I need your help.......

2005 tC, 90,000 miles
here is what happened toady

put in NGK spark plugs at work
drive home everything was OK

put in new Costco battery and cabin filter after dinner
now the car won't idle

When I start the car, the idle is low (about 400-500 rpm) and the car rattles, then engine dies. If I put into gear engine dies.

I have done this kind of stuff to other cars before and I have never run into any problem.

I checked the fuse boxes next to the battery and under dash. Every fuse is fine.

Anyone knows what went wrong.

Thank you in advance for your help.

 

http://www.club-tc.com/forums/engine...ull-reset.html

I found this article on ECM reset. Is this correct?

 

the reset is just let the car idle for 5 to 10 minutes, i did that when i installed my Injen CAI.
i don't think u need to do that when u install battery.

next time when start the car, let the car idle for 10 minutes, It wouldn't hurt to try.

 

Let me answer myself.

The problem came from I install the new battery too fast. Car computer (ECM?) did not reset so the idle is rough.

I search online and found out this is common problem for DIY battery change.

Solution:
disconnect negative from battery.
wait at least 5 minutes
connect negative on the battery
start the car
let it idle for 15 minutes (ECM will re-learn)
drive for 10 to 20 miles
done


Next time, I will replace the battery slowly. I will make sure there is at least 5 minutes before putting in new battery.

I hope this will help someone down the road.