SunBug74
New member
Having looked through a lot of threads here for what I'm experiencing, I'm just gonna ask. Either I missed it and someone can point the way, or we can have a brand new discussion. (And yes, I'm new here, and I live in central Florida, just north of Orlando.)
So, background: 2014 VW Passat TDI SE bought used from a VW dealer in 2018. About a year later, get a Carista reader pumping data to my phone after I start having issues. Car went into dealership to have the DPF, DEF pump, and Turbo all replaced under the extended Dieselgate warranty right before I ran out of miles. Finally got it back in April of 2020. Long story of parts unavailability and a lousy dealership mechanic. Then, new disease-inspired office protocols had me not driving the car much for about a year and a half. Carista went missing from my own doing while it's in the shop.
Fast forward to last fall, I start having DPF issues again. Check engine light comes on because it's doing the regen too frequently. I do the passive regen stuff (3rd or 4th gear, 2400 RPM give or take, lots of time on backroads) and it seems to be OK for a while.
Finally, last December, I took a trip to Arkansas to pick up my son from college. It's almost entirely interstate driving. On the way, my DPF light starts coming on. I'll stop, let the car idle for a few minutes, the light will go off, and I'm good for another hour. I make it out there this way. Then on the return trip, in Birmingham, Alabama on I-65, I go into limp mode. Being the bold soul that I am, we completed the trip to central Florida with no turbo, poor acceleration, and a top speed of about 62 MPH.
I (mostly) parked the car and started driving my motorcycle and my college-son's new-to-him Mitsubishi Eclipse while I figured out what to do, not having the money for a delete kit and tune. I do drive the car occasionally, stupidly hoping that I can passively regen the thing to life. The ECU knows better. At one point, my top speed was about 25MPH and I gave up. The Carista turns up again in the garage and I plug it in to find a Measured Soot Load of 59g. Yeah, I don't think they'll do a forced regen in the shop on that...
Over the next couple of months and many YT videos, I determine that I can, in fact, remove the DPF myself and clean it rather cheaply with a dishwasher tab and oxalic acid. It works! I got the DPF back on (subframe did NOT have to be dropped!) and everything hooked back up and the car runs better than it has since Birmingham. The weird thing was that the Calculated Soot looked great, but the Measured Soot was still high. So I took it to the dealership, they did a forced regen, and behold it runs great! Mostly. (The service manager told me most everyone he knows that's out of warranty does the delete and that I should probably do the same.)
So here's where the story goes south. The check engine light is on again. Too many regens. Carista/VAG DPF tells me that any time I accelerate, the Measured Soot Load jumps straight to over 25g. That triggers the regen if it's not already on. On triggering, the Calculated Soot Load magically also goes to 25g. As I drive, the regen does its job, sort of, and the Calculated drops to near 4g over the course of about 15 minutes. Measured continues to rise slowly, but any time I stop, the Measured starts dropping toward the current Calculated Soot Load. Stop long enough and it almost meets it. But, as soon as I accelerate, Measured rises back to 25+g, Calculated continues dropping. If I do not stop, Measured will continue rising and I have seen it exceed 26g. If I'm in stop-and-go traffic (most of my life), then I can get it down to around 5g Measured before the ECU decides all is well and stops the regen. I then accelerate, the Measured immediately goes back up over 25g, and the nightmare starts all over, with the Calculated jumping back up to 25g and beginning to fall.
Now, my theory is that it was happening all last fall, and my long trip didn't allow that clearout properly so my Measured eventually got out of range for a regen and I went into limp mode. Had I found Carista in my garage during that time, I never would have gone into limp mode because I would have babied it.
My question is this: What is most likely the culprit? Just a bad DPF? A bad sensor? Any advice other than delete?
So, background: 2014 VW Passat TDI SE bought used from a VW dealer in 2018. About a year later, get a Carista reader pumping data to my phone after I start having issues. Car went into dealership to have the DPF, DEF pump, and Turbo all replaced under the extended Dieselgate warranty right before I ran out of miles. Finally got it back in April of 2020. Long story of parts unavailability and a lousy dealership mechanic. Then, new disease-inspired office protocols had me not driving the car much for about a year and a half. Carista went missing from my own doing while it's in the shop.
Fast forward to last fall, I start having DPF issues again. Check engine light comes on because it's doing the regen too frequently. I do the passive regen stuff (3rd or 4th gear, 2400 RPM give or take, lots of time on backroads) and it seems to be OK for a while.
Finally, last December, I took a trip to Arkansas to pick up my son from college. It's almost entirely interstate driving. On the way, my DPF light starts coming on. I'll stop, let the car idle for a few minutes, the light will go off, and I'm good for another hour. I make it out there this way. Then on the return trip, in Birmingham, Alabama on I-65, I go into limp mode. Being the bold soul that I am, we completed the trip to central Florida with no turbo, poor acceleration, and a top speed of about 62 MPH.
I (mostly) parked the car and started driving my motorcycle and my college-son's new-to-him Mitsubishi Eclipse while I figured out what to do, not having the money for a delete kit and tune. I do drive the car occasionally, stupidly hoping that I can passively regen the thing to life. The ECU knows better. At one point, my top speed was about 25MPH and I gave up. The Carista turns up again in the garage and I plug it in to find a Measured Soot Load of 59g. Yeah, I don't think they'll do a forced regen in the shop on that...
Over the next couple of months and many YT videos, I determine that I can, in fact, remove the DPF myself and clean it rather cheaply with a dishwasher tab and oxalic acid. It works! I got the DPF back on (subframe did NOT have to be dropped!) and everything hooked back up and the car runs better than it has since Birmingham. The weird thing was that the Calculated Soot looked great, but the Measured Soot was still high. So I took it to the dealership, they did a forced regen, and behold it runs great! Mostly. (The service manager told me most everyone he knows that's out of warranty does the delete and that I should probably do the same.)
So here's where the story goes south. The check engine light is on again. Too many regens. Carista/VAG DPF tells me that any time I accelerate, the Measured Soot Load jumps straight to over 25g. That triggers the regen if it's not already on. On triggering, the Calculated Soot Load magically also goes to 25g. As I drive, the regen does its job, sort of, and the Calculated drops to near 4g over the course of about 15 minutes. Measured continues to rise slowly, but any time I stop, the Measured starts dropping toward the current Calculated Soot Load. Stop long enough and it almost meets it. But, as soon as I accelerate, Measured rises back to 25+g, Calculated continues dropping. If I do not stop, Measured will continue rising and I have seen it exceed 26g. If I'm in stop-and-go traffic (most of my life), then I can get it down to around 5g Measured before the ECU decides all is well and stops the regen. I then accelerate, the Measured immediately goes back up over 25g, and the nightmare starts all over, with the Calculated jumping back up to 25g and beginning to fall.
Now, my theory is that it was happening all last fall, and my long trip didn't allow that clearout properly so my Measured eventually got out of range for a regen and I went into limp mode. Had I found Carista in my garage during that time, I never would have gone into limp mode because I would have babied it.
My question is this: What is most likely the culprit? Just a bad DPF? A bad sensor? Any advice other than delete?
