Weird limp mode with lots of smoke

[kyper]

Happy new year everyone!

Our 2002 1.9D Berlingo has a problem with some kind of limp mode. When the car enters limp mode power is reduced massively. Power does improve above 2000rpm but 70km/h is the limit. It produces lots of exhaust smoke and has a noticeably 'sportier' sound (Seems to me its running very rich or something?). The idle is also very unstable

The limp mode can be activated at any time by simply starting and restarting the car until it activates, and can be deactivated by waiting 15 seconds between a restart. On the road it arises randomly after the car is hot/driven, but i do suspect acceleration also has something as it often activates when entering the freeway/fast roads (wich is VERY annoying).

The codes i got:
P0170 (Torque says: "Fuel trim bank 1")
P1146 (Manufacturer specific, very hard to find any info)
P1351 (also manufacturer specific, but probably glow plugs)

I heavily suspected the MAF, and it did turn out the sensor was dead. After replacing it the car runs much smoother but it didn't fix the problem. Because of this, code P1146 is weird as it points to a broken MAF sensor. It could simply the low quality of my 10$ cheap reader, although i did reset the codes serval times and the code kept returning. The Torque app reads this code as: "MAF sensor circuit supply malfunction". I did a quick test with my multimeter and the supply voltage was fine (maybe a short circuit or something?)
Also did a quick listening test to the injectors with a screwdriver and all of them seem to be firing fine while limp mode active.

The thing that confuses me the most is that the issue is not constant, it just randomly pops up and goes away again whenever it wants.
Anyone might now a cause?
Thanks

[cancunia]

Just guessing here..

The 1.9D has the mechanical injectors so maybe the fuel pump is not supplying the correct amount of fuel (too much)? There's also a 'wax stat' on those pumps to help cold starting, maybe that has somehow got stuck?

[Kieron G]

I think it might possibly be something to do with the EGR. I had a similar problem. Maybe the stainless steel pipe from the exhaust manifold to the inlet is choked with thick black crud. You could test it by removing one of the small vacuum pipes that operate the valve on the inlet manifold which will stop the EGR valve switching in.

[kyper]

I think it might possibly be something to do with the EGR. I had a similar problem. Maybe the stainless steel  pipe from the exhaust manifold to the inlet is choked with thick black crud. You could test it by removing one of the small vacuum pipes that operate the valve on the inlet manifold which will stop the EGR valve switching in.

I couldn't find the vacuum line you were speaking of. I think? it's the green thing on the battery side of the valve, but had no clue how to disconnect it. 
Instead i decided to just disconnect the EGR solenoid and found that 1 of the vacuum lines was already disconnected, so i'm not sure if the EGR system was even functional beforehand.

I removed both vacuum lines and the connector from the solenoid (wich should disable EGR), but the limp mode kept coming back, nothing seemed to change.

[Kieron G]

Ok just a suggestion, if not that I don't know what would be causing an intermittent fault like you describe