Power Loss Mystery (Tdci)

[pion05]

Hi all

I have a 1.4 TDCI, over the past couple of weeks I have noticed on a cold start a little hunting between 900 and 800 settling to 700 after a minute or so, rough idle, also a bit more smoke than usual; the smoke is white and only happens on cold start. Last week I started to notice that when I apllied or came off the accelerator slightly the rev needle was jerky rather than smooth. I have also had stalling issues mainly in reverse but thought this may be down to my driving since I had 2L diesel for 3 years before this car, but not sure now.

After stalling again in reverse over the weekend I decided to put some pro tec aqua diesel system cleaner in drove 60 miles power seemed to improve my mpg certainly did. Next morning started car and cloud of thick white smoke that cleared up quickly but on on the dive home, 60 miles car slowly became more sluggish. Took it out yesterday and having to floor pedal to get it to 60 and RPM not going over 2500, when parked and flooring it the RPM does go up to 5000. Also engine seems alot quieter.

Took it to my mechanic had diagnosis only fault coming up is speed sensor, but noticed when I turn the engine off I get a clicking sound that happens around every 30-60 seconds for a good 5-10 minutes, not engine cooling sound. Thinking EGR could do with cleaning, and ordered new fuel filter but before i start work on car was wondering if anyone had any other ideas about this.

Also is the speed sensor on this car the one with the pin on the gear box? Wanting to buy a new one but there are a few different ones to choose from.

Thanks

[DieselPig]

Thick white smoke is unburnt diesel, how many miles has the car done?

[pion05]

Hi thank for replying

The car as done 158,000 miles

[DieselPig]

Nice! I would take the car to a diesel expert and get them to do a leak-off test. You may find the injectors are worn assuming they are original.

[pion05]

That was my first thought; do faulty injectors not show up on a diagnostic?

[DieselPig]

The diagnostic only shows error codes depending on the equipment used, the injectors do not transmit any information back to the ECU as they are in effect dumb valves.

[Luke Fletcher]

Hey,

i have trouble with my mk7 on this too, its mainly on cold start up it hunts quite bad for 5 10 min, but if i drive off as soon as i start it is settles quickly. i dont have any trouble with stalling and it does blow out a lot of smoke on cold starts but mines petrol so i believe this is normal in cold weather. all m cars have done this.

does anyone know why it hunts like this?? the engine seems to rev with the needle too if that makes sense. the engine just revs up and down. its been like it for months and the car is driving fine and engine sound ok but annoying on cold stars.

Luke

[DieselPig]

Luke your car should not blow any smoke out of the exhaust, sounds like the mixture is too rich. When was it last serviced?

[pion05]

Thanks again Dieselpig, just went out and started the car and the smoke is now very thin and a bit blueish and smelly...phoned my mechanic to ask about leak off test and he said that a dodgy EGR valve could also cause this due to unburnt exhaust fumes left in the system, and that because of the continuous clicking sound we should start by cleaning the EGR since it is probably stuck open...If that does not cure the problem then start looking at the expensive stuff.

[Luke Fletcher]

it only does when cold, just until the engine warms which is like 5 min. it had it in may last year and they guy put a sticker in the car saying at 35000 miles the next service or in 12 months. its due in may for it service. im only on 26000.

i also use tesco momentum fuel, would this be it. this is a higher octain isnt it??

[DieselPig]

Might be the cheap fuel, try using Shell and see what happens.