The fault symptoms are intermittent. Hard to describe but I will have a go.
There is a lag in acceleration on a winding country road each time you decelerate for a bend then accelerate after. This gets very tiresome.
Sometimes after a period of slow, steady driving behind an HGV for example, when you try to accelerate away when the road is clear, the car "Kangaroos" and you have to shut off and not go so fast.
There is a hill not far from my house, sometimes you put your foot down to maintain speed up it and nothing happens for a couple of seconds then the power will kick in suddenly.
As I said, the symptoms are intermittent. That is why I have discounted the turbo or MAF sensors. Yesterday, the car performed perfectly. Tomorrow it may not.
There are no warning lights on and no fault codes.
I've had the exact same issues/symptoms on my car and as you say ,not all the time. But it was frustrating and ruined the pleasure of driving.
I had codes for glow plug number 6 and after i changed it ,i got immediately fault for the relay and the Lamda sensor (O2 sensor).
I ordered the relay and the sensor but also decided since i'd be changing relay,its good to renew all 6 glow plugs as well.
The relay with the plugs came first (before the O2 sensor arrives) ,so i changed them.
It didn't really make any difference to the issues i had.
My mechanic told me that it's probably the O2 sensor thats responsible for the problems i had,cause it gives wrong signals to the ECU.
So finally the sensor arrived and we put it on and all those issues i had (same ones you discribe) were gone since!
PS: To be 100% true,the day i changed the O2 sensor, happened to be the same day i installed a Brabus D6 chip.
I'm not a mechanic but i'm sure my problems solution was a new O2 sensor and not the D6.
In fact ,D6 would make things worst if they weren't fixed by replacing the faulty O2 sensor.
