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Discussion Starter #1
My Cruze has been awesome in its first 10k miles but lately has developed some weird behavior. In the last 700 or so miles its done five regens, or what I assume are regens. In each case when I come to a stop at a light or elsewhere the idle surges very noticeably. This always coincides with the fan running after I shut it off, and decreased mpg, hence I assume the regens. The rest of the time idle is normal. I never experienced the surging once during the first 10k miles; only noticed the fan running after shutdown a couple times. There are no codes and everything else about driving feels totally normal. Is this possibly just happening because I've been doing more short drives with stoplights, combined with winter cold and winter fuel? I'm still getting just under 45 mpg for mostly local short trips and 60+ when on the highway. Has anyone else had this happen? I tried taking some advice from searches here and keeping the rpms up under load during the last time I felt the regen "symptoms" but 100 miles later, it just did another one. Do I need to take it in for a manual regen? Or just keep trying to drive it a little harder and do some highway runs? Would a fuel additive help at all?
 

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Regens do happen much more frequently with city driving vs highway. Without an OBDII device to monitor, there’s no way to be absolutely certain when a regen starts and ends.

Once initiated, a typical regen cycle will last about 10-15 miles of driving at or above 35 mph. In city driving, the regen will take longer especially if you’re doing a lot of stopping for signals.

If you park the car and interrupt a regen, it will take several miles on the next drive to get the engine up to operating temp and then another mile or two for the EGT to reach 1100 degrees in order to trigger DPF regen.

If the car isn’t displaying any warnings or CELs things are probably normal, no need to bring to the dealer for a forced regen. Rather than experiencing 5 different regens, it’s more likely you’ve interrupted a couple of regens multiple times and it’s restarting multiple times to complete a single cycle.

Take your diesel out on the highway for 20-30 minute drives, it’ll love you for it.
 

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Concur with Rivergoer. Take it on a 30-45 minute highway drive and it should be fine. It sounds like several interrupted regen events. It won't throw an error code until there is some extensive soot build up in the DPF.

Sent from my Moto G (5) Plus using Tapatalk
 

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Discussion Starter #4
Thanks guys. Will try to take it on a little road trip soon. I used to be on the highway a lot more over the summer but lately have just been stuck with a lot of annoying local drives. Maybe a good excuse for a cool day trip.
 

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Discussion Starter #5
So I finally got a Scangauge II hooked up and working and it confirms what I could feel anyway. The SG tells me 147 miles average between regens; 45 miles since the last one; 68% soot level already in 45 miles (all highway miles). I wish I knew why it was doing this. I do a fair amount of highway driving and have made a point of doing a little extra to help it out. Even with no CEL, the regens are noticeable and at that rate affecting my mpg, plus I imagine will eventually cause issues. I thought maybe the frequent regens had to do with a turbo failure I had at the beginning of the year, but that is repaired and the dealer did a manual regen following it, and the behavior hasn't changed.
Guess I will watch a while and see. Does any one know at what soot % a regen is triggered?
 

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On the Gen 1, Scan Gauge measures Soot Mass (STM) in grams.

Regen threshold is 20 gms.

For the Gen 2 did they change STM to a percentage?
 

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Discussion Starter #7
On the Gen 1, Scan Gauge measures Soot Mass (STM) in grams.

Regen threshold is 20 gms.

For the Gen 2 did they change STM to a percentage?
The Gen 2 does not have its own X Gauges, and the Cruze STM gauge does not seem to work for the Gen 2. I used the Colorado gauge for soot %, which I had read works on the Gen 2 Cruze, and that one reads in percentage. Maybe I can find a soot mass measure that works on the Gen 2 in grams.
 

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When I had gen 1 diesel, sometimes mine would regen at 100 miles and I had once it was over 1000 miles, I couldn’t really understand why there was a variation, I am guessing weather and fuel, summer vs winter, driving patterns, etc
 

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Discussion Starter #9
For the heck of it I just took the car on a 50-mile highway drive, mostly at 70 mph, tried to keep it lively but legal. Soot % went from 68 to 92. It only dropped in the 2 miles once I got off the highway at the end, back to 90. I'm assuming it triggers a regen at 100% so I'll have to see if it does that tomorrow. Something just feels off with the car and has on and off since the beginning of winter ... sometimes it feels perfect and others it feels like the power band is off. I thought it was because of the turbo but I'm starting to think that was a symptom and not the cause ... but nothing I can really do until the next CEL.
 

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Discussion Starter #10
When I had gen 1 diesel, sometimes mine would regen at 100 miles and I had once it was over 1000 miles, I couldn’t really understand why there was a variation, I am guessing weather and fuel, summer vs winter, driving patterns, etc
Maybe it just really hates winter fuel and colder weather, but mine still seems to be on the extreme side of frequent for not living in a terribly extreme climate or doing a lot of urban driving. Should be getting warmer out soon so that might tell me something. The car was super all last summer and fall.
 

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After your regen today, post what % it reads right after regen completes. One would assume zero % but not necessarily.

On the Gen 1 STM after regen drops from 20 down to 3-4 grams.

Your 147 mile avg regen cycle seems abnormal. Are you driving strictly City all the time?

My worst interval dipped into the high 300’s (miles), average interval was 750 miles with mix of 75% highway/25% city. The low was nearly all city driving.
 

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Discussion Starter #12
After your regen today, post what % it reads right after regen completes. One would assume zero % but not necessarily.

On the Gen 1 STM after regen drops from 20 down to 3-4 grams.

Your 147 mile avg regen cycle seems abnormal. Are you driving strictly City all the time?

My worst interval dipped into the high 300’s (miles), average interval was 750 miles with mix of 75% highway/25% city. The low was nearly all city driving.
I am driving more than 50% highway and sometimes more than that. Even the "city" I do is more suburban and not that bad. Since I started noticing the frequent regens I made a point of taking it out on a few extra highway trips since I figured I wasn't doing quite as many as I had all summer, but it didn't seem to help. It seems to be building a ton of soot under ideal highway conditions if yesterday is any indication. I am fairly certain the dealership did a manual Regen less than 1,000 miles ago as well, which would mean I started back at 0% or close. Since then I have certainly done mostly highway.
 

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I am driving more than 50% highway and sometimes more than that. Even the "city" I do is more suburban and not that bad. Since I started noticing the frequent regens I made a point of taking it out on a few extra highway trips since I figured I wasn't doing quite as many as I had all summer, but it didn't seem to help. It seems to be building a ton of soot under ideal highway conditions if yesterday is any indication. I am fairly certain the dealership did a manual Regen less than 1,000 miles ago as well, which would mean I started back at 0% or close. Since then I have certainly done mostly highway.
If I had to take a guess, you have a stuck open, or sticking EGR valve. Excess EGR will cause excessive soot. How's your DEF usage? More EGR means less DEF needed. To minimize NOx the EGR puts O2 deficient air into the cylinder, which has the side effect of more soot. Less EGR would mean more DEF to take care of NOx as an after treatment.

I have seen much more frequent regens in my manual Cruze than either of the 9sp auto Gen 2 diesels. That is interesting. The manual has 30 regens in 13k miles, the auto has 18 with about 12.5 k miles.

Another possibilty for the difference, it's possible to run lower RPM in town with the manual. Lower RPM under load would tend to generate more soot. The auto won't let you do that, so it seems to be more efficient at minimizing soot.

All that said, my manual is over 400 miles average regen, auto about 700 miles. Your interval is not normal.

Sent from my Moto G (4) using Tapatalk
 

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Discussion Starter #14
I am driving more than 50% highway and sometimes more than that. Even the "city" I do is more suburban and not that bad. Since I started noticing the frequent regens I made a point of taking it out on a few extra highway trips since I figured I wasn't doing quite as many as I had all summer, but it didn't seem to help. It seems to be building a ton of soot under ideal highway conditions if yesterday is any indication. I am fairly certain the dealership did a manual Regen less than 1,000 miles ago as well, which would mean I started back at 0% or close. Since then I have certainly done mostly highway.
If I had to take a guess, you have a stuck open, or sticking EGR valve. Excess EGR will cause excessive soot. How's your DEF usage? More EGR means less DEF needed. To minimize NOx the EGR puts O2 deficient air into the cylinder, which has the side effect of more soot. Less EGR would mean more DEF to take care of NOx as an after treatment.

I have seen much more frequent regens in my manual Cruze than either of the 9sp auto Gen 2 diesels. That is interesting. The manual has 30 regens in 13k miles, the auto has 18 with about 12.5 k miles.

Another possibilty for the difference, it's possible to run lower RPM in town with the manual. Lower RPM under load would tend to generate more soot. The auto won't let you do that, so it seems to be more efficient at minimizing soot.

All that said, my manual is over 400 miles average regen, auto about 700 miles. Your interval is not normal.

Sent from my Moto G (4) using Tapatalk
I'd find it hard to believe that the car could go through a whole turbo replacement atth dealer and have them not notice a stuck EGR, but maybe the turbo issue masked it. It had two codes due to the turbo and one of them was EGR related, but did go away with the new turbo. Is there any way to tell if the valve is sticking with no engine light? Aside from DEF which I'll try to make note of. I haven't noticed anything crazy. I'll top off soon so I can keep better track ... They topped off at the dealer but I'm not sure with how much.
I had wondered that about low rpms. I wonder if I lug the car too much because you can so easily get away with it in these cars (maybe I don't even notice). Even then that wouldn't explain why the soot is still rising rapidly on highway only where driver-input isn't really a factor.
 

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Discussion Starter #15
Update from today: It did indeed go into a regen. My regen status gauge didn't work but maybe I entered it wrong. The EGR temps went way up and the soot level % dropped from 100 to 2. Once it got to 2 the EGR temps started dropping and the "since last" gauge went to 0. From 117 ... so it only took 117 miles of probably 80% highway to build up that much soot. In the 4 miles since the regen it went from 2 to 15 % soot level.
None of the other gauges jump out to me as suspicious, but if there are any parameters anyone can think of that might give a clue, please chime in. I think given the conditions before, during, and after the last two regens I can't blame this on driving conditions or my own driving habits.
I am going to check the air filter this afternoon, though I'm pretty sure they did that during the last oil change.
 

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Discussion Starter #17 (Edited)
I wonder if the bad turbo sent oil into the DPF?
Possible. Maybe that would cause the DPF to think there's more soot than there is?

I'm wondering at this point if I should just take it to the dealer. My hesitation is that I don't think they will want to do anything without a code or obvious sign something is wrong ... i.e., they probably do not want to hear what I learned from my amateur gauge. On the other hand this was something I observed for quite a while without the gauge and would continue to notice gauge or not, and might be relevant to a documented previous failure, so maybe it makes sense to bring it up ASAP? My other alternative is to wait until something major fails again and throw a code which is inevitable I think. My inclination is to mention it to them, and even if they can't do anything, at least it's documented.

Edit: I should add that my Lemon Law window runs out on April 16, and as much as I hate to say it that's concerning me. If the car is never going to be right again I don't want to be stuck with it and take a huge financial hit, sentimental attachment or not. Sometimes I feel like I have the crappiest luck.
 

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Something is definitely not right, it should not accumulate soot this fast. I doubt it would be from lugging, these engines seem to happily run at 1300 RPM even in the 9 speed auto.

Its possible the DPF is damaged or contaminated from the turbo issue, or dealer installed wrong oil? (dexos 1 instead of dexos 2?) But, if so why did the soot % go down to 2% after the regen. I believe these cars use a pressure differential between the upstream and downstream sides of the DPF to determine soot load. If its partially plugged it should not go to 2% I would think.

EGR could be the most likely problem, as the symptoms of surging, higher fuel consumption and rapid soot load accumulation do fit with a stuck open EGR.
Interestingly a failed turbo is a symptom of a stuck closed EGR valve.

As for why you are not getting a CEL I am not sure.
 

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Discussion Starter #19
I actually just had the thought about the oil while I was reading about common DPF problems, and double checked my first oil change receipt from August. Sure enough it says Dexos 1. I don't know why I didn't notice then. It was at the dealership and was the "drive up" type and I reminded the guy multiple times it was a diesel and needed Dexos 2, to the point I felt I was insulting him. I had it changed again at 12k miles (after the turbo replacement) and I did check the part number on that receipt and it is for Dexos 2. I swear the old sticker said Dexos 2 as well though, and I cannot imagine he could have been thick enough to put in Dexos 1 when I reminded him it was Dexos 2 AND it says it on the oil fill cap. I really have no way of knowing now though, because they could have just put the wrong thing on the invoice and right thing in the car. Timing wise it would line up though ... regens got more frequent a couple months after that.

TDCruze I'm inclined to think like you that it would not go to 2% if it were clogged, though. So I don't know if that is the cause or coincidence.

I made an appointment to take it in April 1, earliest they had. I will bring the 6k-mile oil change receipt. Interestingly the first oil change was done at the dealer-operated "quick lube", which is where they send you when you make an oil change appointment at the dealer. I was not impressed. My second oil change was done at the actual dealer service area because the car was already in for something else, and they seemed to get everything right. I hope the dealer stands behind the quick lube; they advertise it as their own service but it is operated by another business which I did not feel good about to begin with.
 

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Have you checked your oil level by chance since your last service? Just want to make sure it's not significantly over filled.
 
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