Dodge Charger Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter #1 (Edited)
Hello, for the past few weeks my Charger SRT8 has developed a breathing or pulsing idle on start-up. The idle seems to slowly bounce from about 650 to maybe 850 rpm, back and forth, slow and methodically, like an inhale and exhale. Drivability seems fine, just the idle that's not working right.
**(Note: Idle RPM Fluctuation isn't always the same as the listed RPM, sometimes it could be 850-1000, or 800-900, the first mentioned example was observed on this morning's start-up)

The fluctuations decrease heavily once the car is placed in Drive, and once everything is up to temp the pulsing seems to disappear or fade to levels that are not noteworthy (At least that is what I noticed sitting in the drive-thru this morning, waiting on my coffee)

To diagnose I've run through a complete tank of gas, and then refueled at a different gas station than before (Chevron) as well as added an octane booster... and the problem remains, so I do not believe it to be dirty gas.

I should mention my mods, I am running an LMI Air Hammer CAI with a fresh filter as of ~2,000km ago, as well as a DiabloSport intune2 with a 91 octane+CAI tune, and a DiabloSport Oil Catch Can.

My intune2 was updated on March 26th and the 91octane+CAI tune was reapplied on March 28th, during that time the car was reverted back to its stock tune and the problems with the idle appeared to be cured. After updating the tuner I reapplied the 91octane+CAI tune in hopes that the tune was not the issue, I was very pleased to see the idle as rock steady for the first few days. The problem stayed away until the 31st when I put a little over 100km in a single trip, some spirited driving, not thrashing it, but definitely a handful of high RPM pulls in autostick.

The pulse; fluctuation; breathing, whatever you want to call it, is quite noticeable audibly outside the car, even my coworker who had previously asked me to change his wiper blades for him has noticed that my car seems to be acting odd. "Your car sounds really sick and tired."

Any help would be greatly appreciated.

Here are 2 in car video clips of my start-ups to take as example:

[URL]https://www.youtube.com/watch?v=lMGDmyD0tnM[/URL]
(Startup, 2nd of the day, after sitting for my 9 hour shift)

[URL]https://www.youtube.com/watch?v=f6htr-IdJ3c[/URL]
(3rd Start of the day, after a 10 min drive and short shop in Home Depot)
 

·
Registered
Joined
·
1,889 Posts
Did this start after you installed the catch can or CAI? To me, it seems like it is idling a bit high if that second video was after it is warmed up. It almost looks like a vacuum leak. Check your catch can lines, make sure they are nice and tight and that the catch can is closed tightly. Also, double check all your work for the CAI install.

If you don't find any vacuum leaks, try taking the tune back to stock for a several days and see if it happens again with the stock tune. If it doesn't come back, you will want to contact diablosport and tell them about the problem.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #3
Did this start after you installed the catch can or CAI? To me, it seems like it is idling a bit high if that second video was after it is warmed up. It almost looks like a vacuum leak. Check your catch can lines, make sure they are nice and tight and that the catch can is closed tightly. Also, double check all your work for the CAI install.
Thanks for the reply, I'm sitting at work eyeing my car in the parking lot and I was beginning to think it may be vacuum related as you said. When I get my 1/2hr break I'll go check the lines for the Oil Catch and do a quick inspection of the CAI, though they have both been on for months without issue. That being said I did empty the catch about 3 weeks ago, so maybe I tweaked something.

Also, to touch on your comment about the video, no I wasn't quite at full operating temp.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #4
Checked my work on the CAI, all appears fine. Tightened up the chamber on the oil catch can, detached and refitted the hoses for the oil catch. Fired her back up and...

Same wonky idle. :vis:

Grabbed my tuner and flashed it back to stock. Will leave it on the stock tune until DiabloSport gets back to me or until the idle spoils again. It looks like every time I make a change on the tuner it magically repairs my idle for a random length of time. So for all I know it could just be a matter of time before my idle goes sour it seems.


Thought I did notice something, it may not be new though. (I have awful hearing, its actually a problem)
While I was shoving my head into the depths of the engine bay attempting to listen for vacuum leaks I heard an awful lot of rapid ticking. My buddy with a 5.7 Hemi Ram tells me the ticking is just a Hemi thing, a fact of life, but I'm curious to hear opinions on the ticking.
 

·
Registered
Joined
·
1,889 Posts
Yes, hemi tick is common. It's nothing until you install a cam though, then it sounds like an angry sewing machine lol.

Just out of curiosity, how many miles since you changed your spark plugs?
 

·
Registered
Joined
·
13 Posts
Discussion Starter #6
Yes, hemi tick is common. It's nothing until you install a cam though, then it sounds like an angry sewing machine lol.

Just out of curiosity, how many miles since you changed your spark plugs?
Shouldn't be more than 34,xxx kilometers on the plugs... So like, 21,xxx miles I believe that works out to? I really hope it isn't them as that's 16 of something I don't really want to buy right now haha.
Though I guess that would be a better alternative to some other heavy repairs. Any recommendations on a good plug for the 6.1?

Does anyone know if writing a new tune to my PCM with the tuner forces a cam/crank sensor relearn? Met a 300 owner at lunch who said he had a rough idle and the odd long start until he swapped his cam position sensor, but to deal with it beforehand he would disconnect the battery for 15 minutes to force a cam/crank relearn and it would keep the issue at bay for a while.
 

·
9 Second Club
Joined
·
32,307 Posts
What happens when you put her in D, does it still have this issue or is it only in P or N ?
 

·
Registered
Joined
·
13 Posts
Discussion Starter #8
What happens when you put her in D, does it still have this issue or is it only in P or N ?
Issue is most prevalent in Park/Neutral, once in Drive or under load my RPMs appear steady. Though if I put her in D when she is still cold it almost feels like its still fluctuating but not nearly as strong as when its in P or N. Tach visibly bounces in P or N, but only twitches in D.
 

·
9 Second Club
Joined
·
32,307 Posts
First thing I would do is reinstall the tune. That should clear the cars adaptives and help determine if its tune vs mechanical
 

·
Registered
Joined
·
13 Posts
Discussion Starter #11
Flashing panel light was probably due to the framerate of my camera, but who knows.

I've been bouncing emails back and forth with DiabloSport and they should be pouring over my log files right now, so hopefully I will have an answer soon. I will be posting my resolution and experience with DiabloSport in here as well as in its own separate post should anyone encounter similar issues.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #12
DiabloSport FINALLY got back to me with a custom tune, idle seems solid, car seems feistier than ever. Will report back after a week of hard driving to see how it holds.
 
1 - 12 of 12 Posts
Top