[MRO1791]

How bad is the bucking? Both my CTDs do minor fluctuations during regen. My Cummins is by far more severe, especially if in Cruise and going downhill. Some fluctuating is normal, yours seems more than that. Induction side, and exhaust side leaks could contribute, but seems you have looked at that already. Do you have the most recent recall??

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[Barefeet]

They re-flashed the ECM in June. It's especially bad when driving 20 to 40 mph on a slight uphill. It is bad enough that my wife complains and I am embarrassed to have anyone riding with me. I had the service manager ride with me so he could see what it is doing. The car never did this until last December at about 53k. and it started right after I took it in for the recall that they had back then.

 

[Spoolin6Spd]

Sure is too bad diesels come with all this crap these days.... [emoji20]

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[VtTD]

Edit: Didn't read the rough running engine and CEL you mentioned. That does not seem normal. Mine is as described below, but bucking only. I have been getting a CEL lately during regens, but it's the NOX issue (always sensor 1 and/or 2 codes).

Yeah mine was fine originally then started this problem a few years ago. Exactly as you describe. Also at rock bottom RPMs at higher speeds (ie 50, 55mph - although not as bad as the 20-40mph range you indicate). Dealer didn't know. Didn't get any real answers here. I think it's common though. It's annoying, but has not seemed to get any worse since it started. I'd just leave it if I were you. If this was a higher production car there would probably be a more straightforward answer as to why it's happening.

 

[MRO1791]

They re-flashed the ECM in June. It's especially bad when driving 20 to 40 mph on a slight uphill. It is bad enough that my wife complains and I am embarrassed to have anyone riding with me. I had the service manager ride with me so he could see what it is doing. The car never did this until last December at about 53k. and it started right after I took it in for the recall that they had back then.

I'd make sure you get the newest recall, the prior one specifically was suspended since it was causing problems. I have the newest recall flash on one of mine, it's been running fine, perhaps even a slight MPG increase. I personally did not have issues with the prior suspended recall on either car, one of mine is still running it, but I'll be getting it also updated soon. It is possible that the reflash will make things better for you, and being a recall, it's no cost. Good luck, and if you do it, let is know if it helped.

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[MRO1791]

Sure is too bad diesels come with all this crap these days.... [emoji20]

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Yep, thanks to the EPA and junk science for the most part..

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[Barefeet]

I'm not sure if there is a newer ECM flash since June, but the car goes back in a couple of days I will ask them. The code 2453 which I get during every regen is DPF pressure sensor part number 55570092. The service dept. says it tested non responsive. The new one they put in did not help.

 

[dougc905]

The service dept. says it tested non responsive. The new one they put in did not help.

Maybe the port on the ecu that the sensor is attached to is bad => bad ecu

 

[theonlypheonix]

I'm not sure if there is a newer ECM flash since June, but the car goes back in a couple of days I will ask them. The code 2453 which I get during every regen is DPF pressure sensor part number 55570092. The service dept. says it tested non responsive. The new one they put in did not help.

Confused... the new one did not help what? In fixing the bucking problem or with the test of the sensor responsiveness?

Along with the emission recall there is the NOX1 sensor replace, reprogramming and also a manual Regen, do you know whether everything was completed? I might suspect that, given the number of miles on the clock, maybe the EGR is is full of carbon and sticking but also the MAP sensor would probably need cleaning?

 

[Barefeet]

The NOX 1 was replaced just before the recall. They said they now don't do the manual regen because when they re flash the ecm it memorizes the soot level. When I said replacing the sensor did not help I meant that the next regen was the same as before, lot of bucking and CEL came back on (code 2453) I took the car back today and they gave me the new Malibu courtesy vehicle. I did tell them to check the EGR. I expressed my concern that they would just throw parts at it and this was going to be expensive. They said that they are working with the engineers at Chevy and they would keep me informed. I wondered about the MAP sensor, you are probably right that it should be cleaned, however, I think they tend to replace parts rather than clean them.

 

[MRO1791]

The NOX 1 was replaced just before the recall. They said they now don't do the manual regen because when they re flash the ecm it memorizes the soot level. When I said replacing the sensor did not help I meant that the next regen was the same as before, lot of bucking and CEL came back on (code 2453) I took the car back today and they gave me the new Malibu courtesy vehicle. I did tell them to check the EGR. I expressed my concern that they would just throw parts at it and this was going to be expensive. They said that they are working with the engineers at Chevy and they would keep me informed. I wondered about the MAP sensor, you are probably right that it should be cleaned, however, I think they tend to replace parts rather than clean them.

I'm calling BS on the dealership saying they don't do the manual Regen, it's on the recall notice as work to be performed, and reset of the fuel trim. If they didn't do it, that right there could be the problem. My dealership did the service regen with mine. Snipesy came up with a plug-in for the Torque app, I use that and can do my own service Regen. It's not difficult. I'd ask them again about this, and demand they do it, and reset the fuel trims. Good luck.

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[CruzeDan]

The instructions for the first recall do not say to do a manual regen. I didn't when I did mine, had no issues. When I did the recall for the recall I did a manual regen, as it was in the instructions that time. Again, no issues. As for the OP, there is another post about this topic on the forum. My car bucks rarely during regen, it happens occasionally at a certain speed, around 25, and a certain RPM. I haven't noticed it in quite a while. I think it is just a quirk of how they are performing the regen. Your car probably has additional issues though looking at the CEL and codes.

 

[justin13703]

Mine bucks during a regen too. It doesn't seem speed related, but more throttle position related. Under light throttle is when mine does it.

Best thing I can tell you, is when it starts bucking, run the absolute piss out of it. When I do this in mine I guess it makes the regen complete faster because of the higher heat and within a few minutes it's not doing it anymore. You're not going to get anywhere with the dealership. No one knows why they do it, and why some do and some don't.

 

[Barefeet]

Mine bucks during a regen too. It doesn't seem speed related, but more throttle position related. Under light throttle is when mine does it.

Best thing I can tell you, is when it starts bucking, run the absolute piss out of it. When I do this in mine I guess it makes the regen complete faster because of the higher heat and within a few minutes it's not doing it anymore. You're not going to get anywhere with the dealership. No one knows why they do it, and why some do and some don't.

Speed definitely helps, however , I don't want to do an extra 20 miles of expressway driving every 150 miles. They need to fix this problem. The car is still in the shop. l will post any results. Thanks for the suggestions

 

[justin13703]

Speed definitely helps, however , I don't want to do an extra 20 miles of expressway driving every 150 miles. They need to fix this problem. The car is still in the shop. l will post any results. Thanks for the suggestions

I don't drive any extra distance. I just run it harder for the distance I'm going. Yeah it's a stupid issue that shouldn't happen but I personally don't want to spend money on this issue.

Something I notice, since I have an intake I can hear a lot more engine/turbo noise. When the car gets into one of these bucking fits, I can actually hear a small amount of compressor surge from the turbo. So maybe the throttle blade is involved somehow in this bucking issue.

 

[Barefeet]

Keeping the RPMs up does disguise the rough running. I sometimes use the manual shift.

 

[sailurman]

80K Miles. Have not had any bucking yet. And, I do a lot of around time driving.

 

[LulzT1]

Mine bucks during regen at low-er speeds (like up to 35mph), I'm usually on the highway so I don't notice it until I get caught up in traffic. I usually keep a good distance between me and the next car so I can coast between and minimize the bucking. As long as I don't get an CEL, I'll live with it haha at least you can work around it.

IMO, it got way worse after the most recent NOx recall and flash I did back in May. Not sure if anyone else noticed that.

 

[Barefeet]

Update. After a week in the shop, Chevy engineers recommended replacing the "catalytic converter-GM (12659575). This was covered under warranty, the bill would have been $1743. The car did a regen yesterday and there was no change, it still runs rough and the CEL cane back on code 2354. I will take it back again.