05 Mustang Gt Alternator Swap Issue

[Skarlet2005]

New to site ... Found an old thread via google about the "infamous camshaft position sensor" and it helped me a lot! Thanks!!! I have a 05 Mustang GT - got a code for camshaft position sensor (340) - changed it out - cleared engine code - code came right back when I jumped on highway next day. Went and tested my battery and alternator. Battery good, alternator bad. Replaced alternator and code cleared on it's own, car is no longer "bucking". Now ... I'm having another issue since I switched out alternator two days ago ... hoping y'all may have some advice.

When I don't have clutch pushed in and/or I'm out of gear, my car drops down to like 300-400 rpms ... feels like it's going to stall on me but doesn't. If I'm just sitting, idling, the rpms will recover quickly and shoot up to around 900-1000. I've never had an issue like this. No engine codes and car is running great except when I come to a stop and then my rpms just drop quickly to 400ish and it acts like it's about to stall. Also my AC will go from blowing nice and cool to warm. Really strange. Any ideas?

 

[Bullitt95]

The idle issue could be due to a dirty throttle body so I suggest you clean it thoroughly especially between the blades and the bores.
The AC blowing warm could be related to the low idle not spinning the alternator quickly enough for the electrical system to provide full current to the electric fan. This would slow it down and not allow it to pull enough air through the AC condenser to cool the circulating air.

 

[cmann]

+1 on cleaning the TB. Also clean the MAF sensor as well. If you disconnected your battery when installing the alt, perhaps the car might have to relearn it's idle again. There is a procedure in your owners manual as to the process of teaching the idle that involves running the car at certain rpms with and without the AC turned on when you first start it after having the battery disconnected. There is also a process to recalibrate the gas paddle a well (if you search this forum you should be able to find it)

 

[nbk13nw]

I had the same idle issues. Removed and cleaned the TB and it all cleared up. Even though it did not look that dirty at first glance... behind the blades was enough build up to disturb the air flow causing it to think the car was lean and it was dumping more fuel to compensate. A quick and cheap fix for me.

 

[Skarlet2005]

Thank you guys! I will try all the above. I really appreciate your advice ... this is a great site!