Hello all. My 2007 Ram 2500 with 5.7 and120000 miles has a rough idle. You can watch the tach and see a variance of 100-200 RPM. I currently show no codes. My previous truck, 2005 Nissan Frontier had a similar issue and it was the Mass air flow sensor was dirty, it also showed no codes. Anyone have any tips on this. It would be greatly appreciated. Thanks.

 

Could be several things - worn plugs, dirty throttle body, dirty pcv. Start cheap.

 

Have you checked your IAC to see if that needs cleaning? It's located right under the tps. Takes 5 minutes to check it.

 

Have no idea what an IAC is. Can you explain?

 

IAC- Idle Air Control valve aka TPS- Throttle Position Sensor. I prefer TPS.

I believe in your truck the TPS is built into the throttle body. It is the plug that plugs in from the left onto the right side of your throttle body. It should be the only electrical plug to the throttle body. The TPS is not serviceable since it is built into the throttle body.

Clean the throttle body.
Clean the TPS male and female connections with electrical contact cleaner.
Clean the IAT-intake air temperature sensor. Located directly behind the alternator on the front side of the intake resonator box (the only electrical plug going to the black box with "HEMI" written on it).

FYI
1. The PCM (aka Powertrain Control Module) sends the TPS a 5 volt reference voltage.
2. At idle, the TPS is sending a 0.26 volt signal back to the PCM
3. At WOT, the TPS is sending a 4.49 volt signal back to the PCM

I had similar problem as you have with the small fluctuation of rpm. It happened AFTER I cleaned the throttle body. The TPS plug must have gotten dirty resulting in voltage loss, which is the cause of the rpm issue. I haven't had a problem since I cleaned both electrical ends with contact cleaner. I was able to verify that my electrical connection was dirty, because when I initially cleaned the electrical connections the plug did not want to go in smoothly or seat. So I cleaned it more and then it finally went on smoothly and seated.

Many people are adding an extra ground to the throttle body, because they are unable to get clean ground through the TPS connection.

 

Your engine does not have a TPS because the throttle is controlled by the computer. There is no direct, mechanical linkage from the right pedal to the throttle body, thus no TPS (and no IAC).

Regardless of nomenclature, bad grounding is likely the culprit. This is assuming you have done the normal preventative maintenance of spark plugs (you have 16), pcv and egr check, vacuum leaks, etc. Go to: https://dodgeforum.com/forum/3rd-gen...r-download.html You have an 07 (for which there is no manual listed) but the 06s are very similar, functionally. A few electrical differences but those are covered by the 08 manual...

I smoothed out my idle by running a ground wire from the throttle body to a good ground on the fender. The problem is this: Over time, corrosion inhibits the path between various sensors and actuators (adding resistance to the DC circuit(s)) , causing a more sluggish feel in the engine. Cleaning the terminals will reduce this resistance. I tried that first, but the 14AWG wire I ran from the top left TB bolt to the right fender ground made a lot more difference than the connector cleaning (for me at least).

Remember the preventative maintenance. As MikeHTally said - start cheap first!

 

You are right it is drive by wire (electronically controlled), however there is an electronic TPS built into the throttle body and you can not buy it separately. It is not a servicable part by itself, but it does exist. I think somewhere 05-06 is the last of the mechanical TPS for the Rams.

The PCM sends a a 5 volt reference voltage and based on the throttle position, the voltage changes. See my earlier post, which is based on the service manual.

You can read about the TPS below.

http://www.picoauto.com/applications...e-control.html

http://www.enduringautomotive.com/tps/ Shows you how to test the TPS.

 

From what I have gathered from reading alot on here, many of these Gen 3 rams have a rough idle from time to time...I recently helped mine by simply cleaning the throttle body up again, as well as both sensors that were attached to it, and also the air sensor on the air duct housing..seems to have helped, we'll see how long this lasts