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15' PW 1500 RPM Stumble
Posted: Tue Apr 26, 2016 10:36 am
by Sweet5ltr
New member here (so hello everyone), owned a 15' Challenger SRT 392 prior to the 15' PW. My 15' SRT was a 6-speed so no MDS. This new 6.4 has a very, very noticeable hesitation/miss/bucking syndrome around 1,500 RPM and under light throttle. Anything other than light throttle and it's perfectly smooth, no symptoms at any other throttle position or +/- 300 RPM. Is this somewhat normal for MDS in a 7,000+ pound vehicle? Really enjoying the truck so far, it's been one of my best purchases. Needed a truck to tow my custom Jeep Willys golf cart, as my girlfriends Toyota Rav 4 '4wd' is really struggling at even 60-65 MPH with our light 10x8' trailer and 800# cart (max tow rating 2,000#).
Re: 15' PW 1500 RPM Stumble
Posted: Tue Apr 26, 2016 1:20 pm
by Sumbeach84
How many miles are On it?
Re: 15' PW 1500 RPM Stumble
Posted: Tue Apr 26, 2016 1:20 pm
by Low_Sky
When the MDS kicks on, the tone of the engine will get a little lower, more of a grumble. If you have the EVIC on the real-time MPG screen, you'll also see the live MPG number jump up when it turns on. In my 2015, the MDS really only comes on at highway speed if I am off the throttle completely. If I can cruise over flat ground at 45-50 (which I almost never do) it will come on and stay on. In city driving, it probably comes on when I am coasting up to stop signals, but I pay less attention to it in city traffic.
MDS in a truck this heavy, tall and on off-road tires is kind of pointless. It almost never works as advertised, cruising around on four cylinders sippin' gas like a wanna-be Prius.
Re: 15' PW 1500 RPM Stumble
Posted: Tue Apr 26, 2016 1:29 pm
by Sweet5ltr
Sumbeach84 wrote:How many miles are On it?
3,000 miles. Purchased last week. The condition is repeatable, slow speed, light throttle (school zone conditions) and it'll start to buck around this RPM range until I tip into more throttle then it clears completely. I'm thinking MDS as I have no idea what else it could be other than possible fuel mapping/throttle position sensor? The truck runs smooth everywhere other than with light load and throttle at this RPM range, which is typical for stop-and-go traffic.
Re: 15' PW 1500 RPM Stumble
Posted: Tue Apr 26, 2016 1:46 pm
by Sweet5ltr
Yeah, MDS is practically an inside joke. No one purchases a PW for generous fuel economy.. Honestly, it doesn't get terrible mileage, as my Power Stroke F450 at work gets around 11.2 MPG. We're getting around 13-13.5 driving around town currently. Got 14 MPG on the interstate running 75 MPH. I'm sure a tonneau cover may help it squeak out another mpg...
Re: 15' PW 1500 RPM Stumble
Posted: Tue Apr 26, 2016 1:58 pm
by Will
I'm not certain that is the MDS, MDS is more for highway cruise/coasting. At that low of rpm and going as slow as you indicate, I'm wondering if it is in a too high of gear. If you give it more throttle, does it feel like it drops a gear immediately and goes or can you tell if it stays in the same gear, as in the rpm smoothly climbs? I would try mimicking 1500rpm in various gears using the manual shift as well. Maybe have the dealer check the shift points. However, with all the electronics nowadays, they do funny things and will for the life of the vehicle and never cause an issue.
Re: 15' PW 1500 RPM Stumble
Posted: Tue Apr 26, 2016 2:12 pm
by Sweet5ltr
Will wrote:I'm not certain that is the MDS, MDS is more for highway cruise/coasting. At that low of rpm and going as slow as you indicate, I'm wondering if it is in a too high of gear. If you give it more throttle, does it feel like it drops a gear immediately and goes or can you tell if it stays in the same gear, as in the rpm smoothly climbs? I would try mimicking 1500rpm in various gears using the manual shift as well. Maybe have the dealer check the shift points. However, with all the electronics nowadays, they do funny things and will for the life of the vehicle and never cause an issue.
It does it all varying MPH regardless of gear, it was slightly bucking around 65 MPH yesterday and again this morning running 20 MPH through a school zone (always around 1500 RPM and light throttle). Engine could already typically be running lean with this light throttle load do to fuel mapping, maybe even fuel quality could come into play (Going to fill up at a different station next time). The truck runs great other than this, so I'm thinking possible reflash? The truck did it slightly before, but it was barely noticeable. Now, it's jerking the truck around but i'm not losing RPM and it's cleared as soon as I tap the throttle. I have an OBDII scan tool, need to plug it in and see the AFR during this issue
Re: 15' PW 1500 RPM Stumble
Posted: Tue Apr 26, 2016 2:38 pm
by waldo
My 16 "surges" at around 13 mph when creeping uphill around 1000 rpm. I only notice it when going up the mountain to my cabin or on WV forest service roads.
It's a fight between the electronic throttle, the PCM and the trans. I hate the PCM and how it makes the trans shift on that truck.
I haven't gotten around to taking it back for that yet, but I will.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 8:49 am
by Sweet5ltr
This morning, drove it and no issue! What's the deal here?
Thanks everyone for the insight, maybe the self-tuning cured itself? Doubt it, but it's a possibility.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 10:07 am
by NickTF
If I had to wager a guess the only thing you're experiencing is how goofy all the electronics have made the truck act. I came from a 12 second 12v cummins truck which had its share of goofy behavior as well. If you're really concerned take it to the dealer but my instinct says it is just a 14+ power wagon being a 14+ power wagon.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 10:20 am
by LagunaH1
Sounds like the same thing my truck does (mine is a '16)
The symptoms I've seen are very very similar to yours: at light load (and ONLY under light load) it seems like it is having a hard time deciding which gear to go to. -Combine that with the truck's tendency to want to hold gears under load rather than down shifting. I've encountered this a few times (3 or 4 times that I can recall) and I'm pretty much just working around it at this point.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 10:51 am
by OffroadTreks
Sounds like the MDS to me. Hit tow haul and turn off traction control and just drive around like that. It will be like a whole other truck. It's rare that I don't drive with tow/haul on. Plus it turns off the MDS by default and the shift points are better.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 11:58 am
by LagunaH1
The "thing" I'm experiencing is not cylinder deactivation. Cylinder deactivation sounds (and feels) very different and stops instantly when I add a bit more throttle. The "stumble" I have experienced is much more pronounced and takes a few seconds to power out of, downshift, etc. - At least on my truck
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 12:14 pm
by Will
LagunaH1 wrote:The "thing" I'm experiencing is not cylinder deactivation. Cylinder deactivation sounds (and feels) very different and stops instantly when I add a bit more throttle. The "stumble" I have experienced is much more pronounced and takes a few seconds to power out of, downshift, etc. - At least on my truck
Like putting a manual shift in too high of gear? That's what I was thinking the way this was described by the OP.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 12:17 pm
by OffroadTreks
Man all these problems with the '15 folks are having. Knock on wood. Problems I don't have. Makes me nervous.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 12:19 pm
by LagunaH1
Kind of yes, and then engaging the clutch too quickly.....
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 12:48 pm
by cruz
MikeKey wrote: It's rare that I don't drive with tow/haul on.
X2
Unless I'm maintaining 55mph or more, my tow/haul is always on. It drives so much better on .
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 12:48 pm
by waldo
MikeKey wrote:Man all these problems with the '15 folks are having. Knock on wood. Problems I don't have. Makes me nervous.
If I had a time machine, I'd go back and buy 2 07 trucks and preserve the second one. I really like my 07 better than the 16.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 1:03 pm
by Sweet5ltr
The truck is great other than that issue, so I can't complain. It may have been a bad batch of fuel, without it repeating the issue it's difficult to pinpoint until my next fuel up (which is frequent in a PW). My girlfriend loves driving it around, which she couldn't do in my 15' SRT. All in all, I'll keep ya'll posted on the results when I take it into the dealer. Thanks everyone.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 1:07 pm
by Sweet5ltr
Sweet5ltr wrote:The truck is great other than that issue, so I can't complain. It may have been a bad batch of fuel, without it repeating the issue it's difficult to pinpoint until my next fuel up (which is frequent in a PW). My girlfriend loves driving it around, which she couldn't do in my 15' SRT. It's extremely comfortable, and drives excellent for a 2500 (comparable to a 1500!). All in all, I'll keep ya'll posted on the results when I take it into the dealer. Thanks everyone.
Re: 15' PW 1500 RPM Stumble
Posted: Wed Apr 27, 2016 1:23 pm
by RustyPW
My '13 GC TrailHawk with the Hemi does a strange thing. Cruising along in drive, at any speed, light load. You can feel the torque converter lock and unlock at times. It feels like a stumble. The service manager told me to just manually down shift it when it does it.
He says that it's hunting. The program in the ECU is the fault. A reflash didn't help it.
Re: 15' PW 1500 RPM Stumble
Posted: Thu Apr 28, 2016 8:54 am
by Sweet5ltr
Driving it again this morning, it was really 'lugging' around 1100-1300 RPM @ 25-30 MPH in 3rd gear. Tow/Haul mode was on, still experienced issue with very light throttle running 50 MPH. Hmm. . . I'm running out of ideas, maybe throttle or fuel mapping/TPS? My SRT's 6.4 with 485HP never experienced any of these issues. Same issues come up on various 6.4 related RAM forums.. Going to try a few other solutions before I give my truck to a dealer and it sits a few weeks in the service department, and still comes back with the same problem lol. Going to run 89 octane and at a different station on the next fill up and see if that makes a difference.
* Actually, many are experiencing the same issue on the RAMFORUMZ that own PW's... Still no actual solution.
Re: 15' PW 1500 RPM Stumble
Posted: Thu Apr 28, 2016 9:49 am
by Will
What octane have you been using?
Re: 15' PW 1500 RPM Stumble
Posted: Thu Apr 28, 2016 10:03 am
by Sweet5ltr
Will wrote:What octane have you been using?
For the first time in my life, 87..
Z06 Corvette, Saleen Mustang, and SRT Challenger were the last three cars i've owned.. I also own a 69' Plymouth Road Runner with a 440 + B/T Turbo setup. Obviously, premium has been a staple! Thought this engine was detuned to run optimally on 87, but it looks like it is actually supposed to run 89 (judging off other forums). If this clears it up, then that may be a solution to other owners, we'll see.
Re: 15' PW 1500 RPM Stumble
Posted: Thu Apr 28, 2016 10:16 am
by OffroadTreks
Supposedly the SRT 6.4 is not the same as the truck 6.4 ¯\_(ツ)_/¯ At least Ram keeps repeating that it's a whole new motor.
I generally run 87 around town, and then switch over 89 when towing.