I bought a 2005 300C at the end of 2017 and drove it back from Alberta. Once I got back and had it pass safety I noticed that there is a strange pulse-like RPM/Speedometer drop when I am accelerating. Even when I am idling and in park if i give it gas and hold it constant at lets say 1.5RPM it will dip for a bit to like 1.2RPM's then back up, then dip, then back up at a constant rate. It can be fairly annoying when I put the pedal down to accelerate heavily and notice it because you can hear the exhaust noise dip as well see the speedometer not going up at a constant rate either. Doesnt matter if it is warm or cold but sometimes it isnt that bad and other times you can really notice it. It's a hard to explain problem but I will post a video of the idle. I have checked all my grounds and got all my sparkplugs changed but still has the issue. I have a check engine light on due to the CO2 sensors not being there anymore as it is a aftermarket exhaust. (I checked codes and thats all that comes up). If I can avoid going directly to a dealer to fix this that would be great as I have put enough money into the problem and would like to solve and possibly even fix it with the help of the community.

Help greatly appreciated!

 

Sorry for the separate reply for the video... New to forums.

 

I am having such an issue as well in my 2008 300 Hemi. RPMs fluctuate in the same way as yours and you can feel it during car in drive. At first I felt it was me not being consistent with my foot position on the pedal, but after further testing in park, I say it is fluctuating. I do NOT believe it to be a fuel issue other than maybe a dirty TC. I intend on removing my TC maybe this weekend and giving it a good cleaning and will repost after doing so. Additionally, I sometimes get what I call a "dead pedal" that I posted about a few days ago (car shows no stored codes at all). I am beginning to feel that it is the TPS part of the TC which (I understand) is internal to the TC and not a remote TPS at the foot pedal. There is also some 5V signal from the TC to the PCM that can go afoul if ground/s are bad.


I am at a loss like you are and may be way wrong on all this so take what I say with a grain of salt and do your own DD. Hope one of us gets to the bottom of it soon. Going dead pedal at a traffic light just sorta sucks bigtime!


BP

 

Thanks for the reply, has been pretty dead on this thread. At least its not just me! I will keep what you said in mind but yeah let me know what you come up with. I haven't had much time to work on it but I will try to update if I find anything new as well.

 

sorry