My d runs rough when it is cold at idle. The rpms are around 400 and it starts to chugg. When I give it gas it doesn't respond right away but then it runs okay. It only does this when it is cold. I just changed the spark plugs, no change and the old plugs look good. Cleaned the throttle body and ran a few fuel injector cleaners through the system. No error codes either.

 

Change the cap and rotor. Also do the plug wires, mopar performance or msd. Hope this helps.

 

Would't it run rough all the time if it were the cap, wires or rotor? Or some sort of check engine code?

Could it be the TB sensor?

 

Not necessarily, once off idle the torque converter will smooth out the uneven firing strokes. Also bad ignition parts won't throw codes until there is a complete miss, not a partial miss. I assume you mean tps not tb sensor, that will cause rpm jumps while driving, not sure about idle but will cause a delayed throttle response and loss of power.

 

You are right, I meant TPS sensor. I was hoping not to have to touch the cap as it isn't in a great spot. I am still a little worn out from changing the heater core.Thanks.

 

Yeah I know the cap sucks to get at, take off your intake, box to the airhat, will make this much easier. Heater core replace=, heater in winter=

 

Could be a bad battery or terminal connection.

 

I'm not sure what you mean regarding battery connection related to running rough when it is cold. Please elaborate.

 

Low voltage or unset voltage will not render the PCM enough power to fully turn on the diode bridge in the alternator, thus the alternator doesn't make enough voltage to run the motor without enough rpm. The PCM doesn't relize the issue so it dies without you keeping your RPM's up until the voltage regulates above 12 volts.

So in other words, check the connections and clean them up REAL good. You could have the battery load tested, but even then I have seen the pass a load test and still be bad.

Lastly it could be the IAC. Take off the throttle body and clean the IAC port out really good as well as all ports, make the thing shine inside and out, install and new gasket, re-install the throttle body. Then do a correct PCM reset.

 

Can I just use a volt meter to make sure I have enough juice? Is it fairly straight forward to remove the throttle body? (I just did the heater core so i'm guessing it should be easy) Does a PCM reset mean disconnecting the battery and holding the key on?