170 TDI Poor start and running problems

[Havinabeer]

Hi all,

I have a 2007 170Tdi (62k miles) which ive owned for the past 3 months. Car has been good up until the recent cold weather. Since then its become very difficult to start (though usually does) and when running the car temp gauge takes a long time to reach 90degrees and will drop of completely again if you drive slowly or get stopped in traffic.

Upon starting i usually have to leave the car for 3-5mins before i can get any engine power sufficent to drive it. There is also a tapping noise from within the engine when first started which seems to disappear shortly after.

This car has a full Audi service history and the plugs were recently changed.

Any comments/suggestions appreciated.

Thanx

[patrickhorton]

In cold weather, the climate control (heater) sucks so much heat out of the engine you need to be burning a fair amount of diesel to replace the heat dissipated inside the car to keep your feet warm.

I have the same engine. As an experiment, set the temperature to 23degrees. Knock the heater fan down to one bar on the speed indicator. Drive the car as normal and you should notice it reach 90deg after pretty much the normal drive time from cold - even on a very cold day. You will need to keep knocking the fan speed back to "1" as even out of "auto" for some reason it speeds up the fan as the engine gets warm. (obviously don't crash the car because your windows are steaming up or cos yur so cold you can't grip the steering wheel ;))

In traffic, the same goes. Knock down the fan speed and the temp will stay at 90. Select Auto and the gauge will fall.

Regarding the tapping, did the car recently get a service? Mine did this tapping/knocking at cold for a week or so afterwards and now it's gone away. It was especially noticeable pulling away on load at lowish revs.

Also it is much easier to stall when very cold and so I give it a few more revs. If I change too early 1st to 2nd it won't pull either. I think this is a "normal" characteristic to do with emissions that is accentuated in the cold weather. It has been like this for the last year so it is not likely to be a developing fault or it would have failed by now.


Hope this helps.

Patrick

[Havinabeer]

Patrick,

Many thanks for your response. I tried your suggestion regarding the heating problem this morning and the car did hold its running temperature much better! Then when turning the setting to "hi" the temperature dropped off again. This was a bit surprising to me as I've owned 2 VAG tdi's (both 1.9 golfs) and this was never a problem so thanx for pointing this out to me.

However, my main problem remains the poor starting and tapping noise when cold. It sounds low down in the engine and now there is also a new noise which almost sounds like a squeaking fan belt. The car was serviced about 4000 miles ago by audi before i bought it. I do have a warranty from the independent dealer where i bought it so I took it back this afternoon. He was snowed in earlier in the week so today was my first opportunity to do so.

No word from them yet as its early days but i'll post up their opinion as soon as I get the car back. Its a bit annoying having only owned the car for 3 months but hopefully i'll get it back soon and have no more probs.

Once again many thanx for posting back.

Havinabeer

[patrickhorton]

You initially said the tapping noise disappears shortly after start-up. Could this just be due to oil draining back to the sump overnight. How long would you say "shortly" is? In the old days you could buy cheap oil filters without non-return valves and the engine would knock until the pump re-filled the oil galleries. I suppose such a valve could start to leak.

How low is your oil level and if you fill it to the max line does it help the problem?

Patrick

[Issac Hunt]

In traffic, the same goes. Knock down the fan speed and the temp will stay at 90. Select Auto and the gauge will fall.




That suggests you have a fault somewhere. All 10 of the VAG cars I have owned never fluctuate at all in 'auto'. The temp always stays rock-solid at 90, no selections on the climate system ever affect the water temperature indication.

[patrickhorton]

Tomorrow I will check the pipe to the main radiator at the front of the car. If it stays cold til the coolant reaches 85deg then I am confindent my explanation is correct. If hot coolant is leaking into the radiator before the thermostat opening temperature then I accept there is a fault.

With the thermostat shut, the only place the engine heat can be dissipated is in the heater matrix. If the heater is able to take more heat out than the engine produces, the thermostat will not open - and the gauge will not reach 90.

I had a B5 A4 for 11 years and it did exactly the same. If you are stuck in traffic, you should not be burning enough fuel to feed the heater on full chat.

Patrick

[patrickhorton]

Got to work (12miles), minus 11deg outside. Used the heater controls to keep the coolant at just below 90. Lifted the bonnet at the end of the journey and checked the rad hoses - top and bottom stone cold. Heater hoses were toasty as was the metal section of the top main radiator hose.
(The top rad hose joins a metal section of pipe which rises to a high point before fallin towards the rad. The hot water rises to the high point due to convection but doesn't spread down hil to the rad.)

Conclusion. The heater can suck more heat than the engine puts into the coolant if you don't do much above 40mph on a cold day. In traffic more than two bars on the fan control and the gauge will struggle to reach 90.

[Havinabeer]

Thanks for your replies everyone. I left car with the independant garage i bought it off last saturday as the car was still under warrenty with them. I have phoned everyday for an update but as of yet do not have a diagnosis of the problem never mind a solution. Below is a summary of what the garage has done/said.

1. Car was subjected to a computer diagnostic. This did not show any faults.
2. Injectors were taken from the car and individually tested both for mechanical function and electrical function. Both tested normal.
3. All other engine components have been given the "Once over"

Lastly they have been suggesting that the DPF is failing causing the poor start and running. However, I wont find out anything further till tomorrow and this does not solve the engine rattle. There was no DPF light on this dashboard to indicate a problem with the DPF as suggested in other posts within this forum.

Once again thanks for your help and suggestions.

[ming]

This statement is from your first post:

"This car has a full Audi service history and the plugs were recently changed."

Did this statement originate from the dealer? I ask, because; there are NO PLUGS in a 170TDI, nor any TDI for that matter. If this did originate there, then I'd take their findings which you include in your latest post with a pinch of salt.

I had starting issues with a 140TDI which I bought from a well known independent. They weren't able to pin point the source either but they did agree to pay for a full diagnostic at the local Audi dealership. I think that might be worth pursuing in your case.

I don't want to raise your hopes, though. Audi, Glasgow couldn't get to the root of the problem either. The indy took the car back. I was bloody lucky, though.

[patrickhorton]

This statement is from your first post:

"This car has a full Audi service history and the plugs were recently changed."

Did this statement originate from the dealer? I ask, because; there are NO PLUGS in a 170TDI, nor any TDI for that matter.

.

I presume plugs meant glow plugs. As these are part of a cold start function it was not completely unreasonable to change them. But they are easy to test and I would only have expected blown ones to be changed - 4 blown plugs??

[Havinabeer]

Hi folks,

Many thanks for all your posts and replies and my apologies for not posting up sooner.

The independent garage where I bought the car admitted defeat and sent the car to Audi. 3 days at Audi and they eventually said that the timing was off. Not by much but by "1 tooth or so". This was a total surprise as I was under the impression that timing never needs to be adjusted on a diesel car and that only the timing belt needs changed according to service intervals.

Anyway the car runs really well now and is much smoother. Starts 1st time and because they were resetting the timing I got a new timing belt and tensioner which I dont have to pay for as car is under warrenty with the garage i bought it from :)

Anyway car now going like a train but thanks again for your help and interest in this problem.