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Discussion Starter #1
Hi

Driving in town, short trip and incomplete DPF regeneration:
I would like to find out how to take care of a diesel Saab 9-5 with a blocked DPF, contaminated with carbon deposit and poor performance.
So far I found out about:
-Check for OBDII codes
-Using fuel additive to lower the temperature to regenerate the DPF quicker.
-Driving regularly about 50 miles on motorway to properly regenerate the DPF (about 3000 rpm for some 30 mins)
-Check the glow plugs and/or replace them (check using a ohmmeter, resistance should be about 1 ohm +-10%)
NB: at 2 ohms the glow plug has lost 50% watts, from about 170W to 85W. It is 50% less effective. Calculations (13V/2ohms=6.5A then 6.5Ax13V=84.5W).

I now need to understand how to get ride of the carbon deposits?
Any suggestions?

I also like to find out if the glow plugs are used within the regeneration process?

Best regards
Jo
 

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If the DPF is blocked then the only way to revive it is to physically clean or replace.
Many folk remove and back flush...plenty of DIY's on youtube.
I believe the glow plugs are used during the regen cycle.
Additives imho are snake oil.........psychological benefit than any real one.
Main failure is due to failed regens on short journey cycles although you should be able to monitor with android DPF info and a v1.4 bluetooth dongle.
On the 9-5 the OBD2 connector will probably need the canbus wiring modified...works great on the 9-3's Z19DXX engines.
Unfortunately regens occur depending on driving cycles and can be from 300-1000miles so there is no guarantee when it will
happen other than monitoring the cycle.
 

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I agree with cjaeterborough that additives will not help.
I believe that the glow plugs can warm up the air in the cold cylinders for easier combustion only.(my opinion)
Try to start a manual DPF regeneration if you have the tool.
If the manual regeneration does not start, then you have to find the reason.
It can be the DPF pressure sensor, or the rubber hose to it.
Even the exhaust temperature sensor can block the regeneration.
If the ECU doesn't get the info that the exhaust is hot enough to start the regeneration, it won't do it.
But you should get fault codes on a diagnostic toll if any of this are faulty.
I had five saab 93 tid and ttid (I still own two) and I had problems with them of course and I kind of know what I'm saying.
If your DPF is blocked it should try to start the regeneration everytime you drive the car, if it doesn't, then your blocked dpf is just the efect of another fault.

And to bust a mith that you need to take the car on the motorway every N days, for N miles, at N rpm:
My wife's 93 tid is the 8v 120bhp.
She is driving only in the city, only short trips and very often the engine doesn't get even warm and that's it, she's at the destination.
It cannot be worse than that for a diesel.
When the DPF regeneration starts,(I can monitor the cycle) the engine doesn't run smooth anymore, it's shaking like not all injectors are working, etc...rough anyway.
So we know that at this point we should not stop the engine. Don't have the option to go on motorway due to small kids, jobs etc, so the car is left in front of the house for 20-30 minutes to run. Also at the exhaust box I can hear powerful "puf-puf-puf-puf" instead of a normal quiet exhaust.
I understand that the ECU gives more fuel in the cylinders in order to increase the temperature in the exhaust which brings the DPF filter up to around 500C.
Anyway, 20-30 minutes later the engine runs nice and smooth again,
DPF saturation 2%, all good.
It has been almost a year since the car runs in this conditions and it's perfectly fine. I had to remove the EGR twice in this period to clean it and that's no surprise.
 

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Discussion Starter #5
Sorry if I wrote to much.
I'll try to be short next time.
Thank you
It would be good to find out if the glowplugs are used during the regeneration cycle.
The last 300 miles have been ok. this is after a motorway trip to clean the DPF.
All the codes are gone and no new one.So I am monitoring it and I will now include a regular motorway trip every 600 miles.
regards
jo
 

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As I said glow plugs are used if you check the WIS...... but that wont be a real issue.
Glow plugs are easily checked with a multimeter.....resistance should be 1-2 ohms....pull connector one probe on the tip and the other on the engine block or earth.
As to the regen process invest maybe £5 in a suitable dongle and then use the android app....it will give you the complete feedback and then you know when its happening and when NOT to turn the ignition off.
Regens can occur at any speed as long as the engine is at temp,Saab chose to do it the "cheap" way by adjusting the engine timing to inject more fuel on the exhaust stroke.
Thats why if regens are interrupted the EX diesel end up diluting the engine oil and ultimately can cause runaways.
 

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Yes I can confirm as cja glow plugs are used , there are certain factors to carry out regen , engine temperature, coolant temperature normally above 65 degrees Celsius, back pressure, if DPF is blocked, and the car has had too many regens interrupted. Then you really have to first check oil level on the dip stick, if above max then as cja says the oil has been diluted, and I would not suggest any kind of regen until such time as you have changed the oil and filter, because yet again as cja says diesel runaway can occur,look on YouTube and there's probably a lot of videos of that .
 

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Discussion Starter #8
Yes I can confirm as cja glow plugs are used , there are certain factors to carry out regen , engine temperature, coolant temperature normally above 65 degrees Celsius, back pressure, if DPF is blocked, and the car has had too many regens interrupted. Then you really have to first check oil level on the dip stick, if above max then as cja says the oil has been diluted, and I would not suggest any kind of regen until such time as you have changed the oil and filter, because yet again as cja says diesel runaway can occur,look on YouTube and there's probably a lot of videos of that .
Hi

What does "cja" means?

Thanks
Jo
 

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There is certainly an impact from exhaust backpressure due to DPF, DOC, NAC and SCR exhaust catalysts, but engines equipped with both DPF and NOx catalysts are still capable of over 28-bar peak BMEP and a best BSFC of less than 200 g/kW-hr. Systems on heavy-duty trucks with the SCR positioned downstream of the DPF can advance injection timing somewhat to lower soot loading on the DPF and improve BSFC, provide more NO2 for passive soot regeneration on the DPF, and rely primarily on the SCR system for deNOX. Such systems still have the capability of active soot regeneration but still rely primarily on passive regeneration.
 
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