Hi everyone!
Quick presentation, I'm Simon a French guy that came for a few months in the states. I came here and bought 2 months ago a Dodge charger RT 2007 98k for 8k in what looked to be good condition. I'm happy with it but TBH I bought it to sell back in France, we don't have those and they cost a lot back there (25k). Myself I'm more attracted by mechanic than power (own a 34hp French car from the 70's in France and I'm fine with that 😁 Renault R4 F6 for the curious) so I never floored it.
But here starts the trouble, as I got more and more confident with having 10 times the HP I'm used to I pushed the gas pedal a little deeper as I got on the highways. In condition of "heavy" acceleration the car jerks like crazy, misfires that for a while I put into account of the esp trying to prevent me to slip as I did not had any check engine light. I later realize it wasn't the case (when I saw the esp light on gravel) but could be a dirty MAF, pedal sensor or faulty MDS transition. I found how to see the pedal reading (by holding the compass button and the note button on the steering wheel together for a few seconds until I get a new menu poping up) so earlier today I floored it just to check if it was the pedal and this time had a check engine light.
Check it with the obd2 and I have misfires on cylinders 1-4-6-7 so all the one related to the MDS.
The idle is good, once at cruising speed (4cyl) or even lower charge but in acceleration (8cyl which I definitely hear the difference because of the flowmaster exhaust the MDS sound transition is obvious) the engine is smooth.
I think I said everything that need to be said and if I didn't I'll respond and try to make it clearer.
If anyone experienced it and fixed it I'd love to hear from you. If you did not but want to put your diagnostic skills to the challenge come in too!
Thank you all, let the hunt for a fix begin!
Simon (may I remind you that if I spelled something or expressed myself badly it's because English isn't my native language so no offense 😁, thanks!)

 

That was understandable, and your english really isn't that bad. Welcome to DF.

Coincidentally enough, the cylinders you are getting misfire codes for, are the very same cylinders the MDS system shuts down....... I would suspect solenoids, or lifters.....

 

I have seen the lifter problem come up on my research but it's often linked with a rough idle, most of the time noise and only affect one cylinder not 4 of them together. Could the solenoids do this?

 

I would more suspect an electrical problem. Maybe the harness for the solenoids is grounding out somewhere, keep them engaged. (and those four cylinders disabled.....) that would explain the codes.

 

I got the code only once because I really floored it otherwise they don't come up if they grounded the engine would always be in 4cyl mode which he's not. It's like if actually does switch from 4 to 8 but back and forth when the load is high.

 

May have been just a fluke then.....If the problem persists, may have to visit the dealer for diagnosis.

 

Yesterday I started noticing rough idle and erratic driving even while idling... Roller bearing signs?
i could do with a dealer as suggested but how many times they change 4 or 5 things before finding the problem?

 

Yeah, dealer experiences are real hit and miss. Finding one with a good 'performance problem' guy is getting more and more difficult. (I used to work with a guy that was a downright wizard when it came to performance problems. You could 100% guarantee that when he said the problem was fixed, it was. I miss him. )

Are you getting any codes at all?

 

Only code I have is for catalytic bank number 1. If I erase the code it take a few days to come back and always does on short trip with cold engine.
The left catalytic converter is not original so I don't know if the problem is the converter or o2 sensor. But could it be related?

 

Anything is possible, but, I rather doubt it. Cylinders are distributed across both banks..... so a bad cat, would only affect two cylinders.