So I replaced the alternator in my '05 tC cuz the other one was making a wine and I'm selling it so I didn't want that to be a problem. I installed the alternator and a new belt and wine is gone but now when I'm at idle the the car revs up and down. Is this a bad alternator?

 

I had the samee problemm..I changed my alternator and battery and checked all the grounds and fuses and never had that problem again but it could be that its trying to heat up the engine faster

 

Well it was like 50 out the day we changed it. I read on google that someone had the same problem and just reset the computer and it was fine. I guess I'll check it tomorrow.

 

mine has always done this, and my volt meter on my turbo timer reads 13.8-14.2 all the time. Im pretty sure its just how the tC steadies its A/F ratio at idle when it is colder out

 

Not to threadjack, because my alt is fine... But mine is having a similar problem where on the first startup of the day if its cold out, and the engine is really cold, it will bounce up and down from 1700rpm-1000rpm, until it starts to warm up and get stable. Is it common for our cars to do that?

 

mine has always done it, a lot of cars to that

 

mine does it also...

 

it is common i believe it is the ecu's way to warm up the car faster.

 

so i kinda been looking around.. and then gave up but maybe u guys know...

my RPM bounces up and down every time i get gas... sometimes the rpm drops so low that the car dies and i have to start it up again... any ideas?

 

mine has never died...

 

Check injectors might need to be cleaned. Also check to make sure the clips are good.