Diablosport Forums

When in drive and ac turned off as well as the defroster off, my 2009 rt challenger likes to go down to about a 500 rpm idle. So I will be sitting a redlight and watch the idle go down to 500 and then after a few seconds, maybe 10 it will go back up to 700. At 700 rpm it is a smooth idle, when it goes down to 500, it gets a little rough. I run the 93 cai tune, thats not the cause becuase I put the stock tune back in and the same thing happened. With the 93 cai tune installed I adjusted the idle rpm for Drive to 750 but it continues to reduce rpm's when at idle and in drive. I know its not a tune issue but was wondering if anyone knows what is causing this and can I run some diagnostics with my laptop and predator to determine where the trigger is for this issue. Again , 2009 Challenger Rt, 30,000 miles, 93 cai tune, catch can, cai, 180 thermostat. Any ideas.

throttle body?

Do you have your vent set to any "floor" position and the fan set to anything other than off? Any floor position (and the fan turned on) runs the A/C even if you don't turn the A/C on yourself.

frankiek wrote:When in drive and ac turned off as well as the defroster off, my 2009 rt challenger likes to go down to about a 500 rpm idle. So I will be sitting a redlight and watch the idle go down to 500 and then after a few seconds, maybe 10 it will go back up to 700. At 700 rpm it is a smooth idle, when it goes down to 500, it gets a little rough. I run the 93 cai tune, thats not the cause becuase I put the stock tune back in and the same thing happened. With the 93 cai tune installed I adjusted the idle rpm for Drive to 750 but it continues to reduce rpm's when at idle and in drive. I know its not a tune issue but was wondering if anyone knows what is causing this and can I run some diagnostics with my laptop and predator to determine where the trigger is for this issue. Again , 2009 Challenger Rt, 30,000 miles, 93 cai tune, catch can, cai, 180 thermostat. Any ideas.

This can happen when the evap canister is purged. Most of the time it will purge while you are driving (not idleing) so you do not notice it. My dodge truck did the same thing. What is happening is when the evap canister is full the system will purge the canister of fumes and put it into the intake manifold to be burned. This gives you a little richer mixture for a few seconds and changes the idle. In hotter weather it purges more often because of the expansion of the gases so if your doing alot of around town driving it will happen more often. I cant remember the last time mine did it so I have not worried about it. This can also happen if the evap system is malfuntioning but you should get a code. I have not gotten any codes so I think it's normal on my truck.

stock throttle body.

ricks wrote:Do you have your vent set to any "floor" position and the fan set to anything other than off? Any floor position (and the fan turned on) runs the A/C even if you don't turn the A/C on yourself.

I have heard this about the window defrost position...never the floor position though. Are you 100% sure?

oilslick wrote:

ricks wrote:Do you have your vent set to any "floor" position and the fan set to anything other than off? Any floor position (and the fan turned on) runs the A/C even if you don't turn the A/C on yourself.

I have heard this about the window defrost position...never the floor position though. Are you 100% sure?

Yes. Look in your manual.

Page 236
https://a.srs20.spx.com/OEM/Chrysler/en ... index.html

oilslick wrote:

ricks wrote:Do you have your vent set to any "floor" position and the fan set to anything other than off? Any floor position (and the fan turned on) runs the A/C even if you don't turn the A/C on yourself.

I have heard this about the window defrost position...never the floor position though. Are you 100% sure?

If your running the AC it kicks the idel up to make up for the load. So if it was tuning the AC on he would not be having the low idel problem.

No, AC is not on nor the defrost. The car just likes to idle in
drive at about 500 rpm but will occasionally jump up to 750 which feels much better. This is on other forums listed with other models using the 5.7 motor going back a few years, the thing I dont see is a resolution, so I have to figure its normal. I am wondering if a sensor is going bad.

I’ve posted the same issue awhile back. I’ve yet to get a straight answer.
I even replaced the throttle body with a CNC ported unit. You can’t adjust it out with the predator. If you leave the AC on with the fan low the idle bumps up and remains at around 700. 09 5.7 RT classic

It seems to be temperature related, when engine is cold, it idles at about 700 all the time, as engine warms up the idle comes down to 500. If its idling at 500 simply shift into nuetral and right back to drive and it will idle at 700.

frankiek wrote:It seems to be temperature related, when engine is cold, it idles at about 700 all the time, as engine warms up the idle comes down to 500. If its idling at 500 simply shift into nuetral and right back to drive and it will idle at 700.

Found this its on a 4.7 but seems like many dodges have had the same problem. The post is by ahasher and it is the 8th post down. they had a TSB on it and flashed the computer and replaced some part. Hope this helps.http://www.dodgedakotas.com/boards/v8/397.html

I'm having the same problem with my 2010 Challenger RT auto. Any resolution??