2010 mazda3 1.6 diesel

Have just done leaking injecter, couldnt get it to bleed, but got it going with easy start.
Idle was ok, but when I took it for a run. It was jerking like it was running on 3 at low revs then picked up. Smell of diesel
turns out that the breather from the cams had come of.
refixed that and wiped down some of the oil off the engine. Took it for a run and it was running ok, then the powertrain light. yellow cog with exclamation mark. Came on, after which it went into limp home mode.
the powertrain light had flashed once on previous test run but not stayed on.
I have been cleanining off the oil, sprayed with wd40 followed bu air line.
dissconected and re connected battery.
But light stays on.
.

 

I would suggest you have it scanned with a good scanner to see what comes up to reduce guessing.

 

Local garage removed all historical codes but 1 remained, dpf filter.
suggested I take it on motorway at 4000 revs in third which would probably clear it. If not would be around £400.
Took it on mw only getting 3000 revs az it was in limp mode, butafter a while got it to 4000 maybe a little more, but couldnt keep this up due to traffic, but ended up doing about 60 miles in third at 3000 + car seems to be running better and returning good mpg 50+ in third, but light is stilll on and still in limp mode.

 

A DPF regen can be done at the workshop with a good scantool. The amount of soot blocking the DPF can also be read with a scantool. There may also be a warning of excessive soot in the oil. This is a calculation based on quiet a few factors and should be reset after an oil change.
In relation to the jerking have a look at the live data from the air temp sensor and the map sensor. (I'm pretty sure your car uses a map sensor) because they get filthy with carbon buildup and even though their outputs are within the limits have a big input on how the car runs.

 

There is no jerkih, I fixed that before going to garage.
cant be booked in till next week. But adbised a really good run on mw at least 50 mins.
then engine light came on, code was dpf so I cancelled that but it came on again.
2 hours + high revs on mw but still the same. Then I read somewhere that it wouldnt regen with engine check light on so I erased that and another jour + on mw.
engine chevk light has stayed off so far buy powertrain light is still on as my scanner does not fetect it, but car is running fine despite all of this.

 

I have put some DPF filter cleaner in the tank which is full of Tesco fuel but I was told by the garage that this doesn't burn effectively and I should fill up with vpower so I am going to use this tank of diesel then fill up with v powwr I may also put some DPF regenerator in and then use the next tank of fuel and see what happens if anything there seems to be so much confusion on the web that it's impossible to say what is the best line forward

 

The best way to clean a CAT is to remove it and have it ultrasonically cleaned. Inside is 2 sections and if it's driven blocked for too long they get pushed together and then can only be fixed with replacement.Prior to the ultrasonic clean they cut a small hole to examine the location of the sections and if OK then go ahead with the cleaning process. I have little faith in using different fuels and additives but good luck.