B6 A4 1.9tdi starts but.....

[twist123]

Hi Guys,

Hoping you can give me some advice, with the cold weather my wifes B6 A4 1.9tdi has been standing a week or so and it starts but only runs for a few short seconds then dies. Its not the immobilizer as thats all working fine (both keys), it seems/acts more like fuel starvation as when I put my foot on the accelerator a bit once its started nothing happens it just grumbles and dies.

Put it on Vagcom and nothing comes up.

Any ideas would be greatly appreciated.

Thanks

[BlackQuat]

When was the fuel filter last changed?

[twist123]

I change it usually every service so probably 10k miles. My wife also complained of feeling a flat spot but not all the time just under 2k rpm. Thought it may be fuel filter or glow plugs but changed fairly recently.

[BlackQuat]

I'd certainly be tempted to try a fresh filter.

[twist123]

Ain't gonna hurt, will do that along with any other suggestions provided, it needs a service so will be doing filters, oil, maybe plugs. Thanks

[quattro tony]

I would check the air shut off flap just in case its not opening fully,you will find this on the inlet manifold , basically the valve that sticks out of the engine cover, they have been known to stick due to dirt, oil contamination.Also , all your glow plugs ok and working?

[twist123]

Is that the one by the EGR? The black thing with the stalk? Cheers mate.

[quattro tony]

yes that's the one, it should be open normally and when you turn the engine off it should close the flap and then release it after a bit but if is sticking it won't open properly, worth a quick check ,

[twist123]

Right guys, problem was the map sensor, I checked the valve Tony mentioned, changed oil and air filter, thought mmm Ill try unplugging the MAF, no difference then found the MAP sensor (if you look at the top RH corner of the engine cover youll see it with a cable out the top like the MAF), unplugged the map sensor car ran fine but no boost, took it out had a fiddle and a quick clean, put it back in, bingo! Car runs perfect.

Will replace anyway as its probably knackered, my part no. for A4 B6 1.9 tdi AWX is 038 906 051 C its 55+ VAT. RESULT, VW part no. is the same and theyre only £20 odd, must be the Audi price I got quoted.

More info: This is also known as a ‘Thrust Sensor’ and is used to measure air pressure within the boost pipes of your engine, as well as measuring the air temperature.

[Turkster]

id also advise sticking some fuel cleaner in it, Redex Diesel, wont hurt!

[quattro tony]

Great to hear u got to the bottom of it, strange diagnostic did not pick it up, maybe it was just working within its limits. Never had to replace one on a pd b4, they are normally ok.

[twist123]

Hmmm, the plot thickens, changed the MAP sensor and it starts fine, runs fine except for the odd blip in revs every few changes. Noticed close to the MAP sensor on the intercooler pipe it looks to be leaking oil where the big metal ring joins the plastic pipe to the rubber pipe, about middle way down the pipe. Also when I rev it at around 3k I get a slight whistle so Im suspecting a vacuum leak?

Cheers guys

[quattro tony]

I would check all the hoses carefully for any leaks , ive seen the lower boost pipe from the turbo split b4. Might be worth giving the egr valve a good clean out

[twist123]

I would check all the hoses carefully for any leaks , ive seen the lower boost pipe from the turbo split b4. Might be worth giving the egr valve a good clean out

Thanks Tony, think the egr is knackered, loads of thick black oil round it and on the black valve stem. Wouldn't surprise me if the inlets full of crud, so a task for the weekend. It's not dumping black smoke since I last checked so is it worth it trying new seals for the egr or just replace?

[twist123]

Ive ordered a new EGR as the seals arent serviceable and it probably needs changing anyway, I also will be cleaning the intake manifold and have ordered the gasket.

Im thinking of cleaning the VNT, just wondering if its easier to while I have the intake manifold off?

Thanks

[quattro tony]

hi , my egr was very coked in crud and the shut off flap, i just gave these a really good clean , I didn't do the manifold and turbo on mine, quite a few on here have with good results.