Poor starting and blue smoke - help and advice
 

I have an 850Tdi CD Auto P reg (Audi engine)

It smokes terribly when outside is cold, despite new glow plugs. Upwards of 5 degrees it is fine, but still has whisps of light coloured smoke.

The strangest symptom is happens when you are going around 75mpg when torque converted lock up is in operation. If you ease off the throttle, then place it down again when the car is on the 'overrun', the motorway absolutely fills with thick blue smoke and the car clear 'chokes' and then fires back into line.

At 50 or 60, it doesn't do it because the car is in effective free-wheel.

Also, it is worse if you have travelled for a while at a constant speed, and once it has smoked, the second time is not so bad.

My thinking is that somehow, oil is being sucked from the intercooler on the overrun, thus choking the combustion. Once clear, it doesn't happen again. The oil, is suspect, is coming from worn Turbo seals. Does this sound reasonable? Not much oil consumed between 5k services, however.

It has approx 270k miles and is due a cambelt change. I am not sure whether the terrible starting is the same thing, or something else as well such as timing

All thoughts welcome!

I can't really comment on the smoke on overrun, but it's likely that the poor starting is probably due to the dynamic timing being a bit off. In practice, unless the weather is seriously cold, the glow plugs have little impact on the car's ability to start.

My 1998 Tdi auto (same engine) only struggled to start when the temperature got to below -10 degrees C but otherwise started first turn. It wasn't until I removed the cylinder head to repair the aftermath of a broken cambelt, that I discovered all 5 glow plugs were completely dead and probably had been for years!

After repairs were completed and new glow plugs fitted, I can't say it's made the slightest difference to starting in normal winter conditions.

For obvious reasons I'd suggest replacing the belts and tensioners asap and you'd normally do the dynamic timing at the same time when the new belts are in place. My guess is that this will probably resolve the starting issue.

Martin

1998 V70 Tdi Auto 224,000 miles

Thank you.

It seems that's the way forward.

Will keep you posted. I've had a quote of £537, excluding new crank pulley.

I communicated with a chap at the local Volvo specialist who said that white smoke was timing issues. I think there are two smoke types here?

https://youtu.be/nkDyc_r1yQ4

Injection pump timing retarded by a large margin . My V70 Tdi was that bad at starting until I advanced the timing . You need the engine at 80C BEFORE you make any attempt to alter dynamic timing , even if the pump is only slightly out mine smokes like a pig & stinks

Just watched the video. The amount of cranking it takes to start yours is ridiculous.
Your pump timing is way out !!!
These start 1st time everytime in all weather conditions if the pump timing is spot on.These don't even need glowpugs and just serve to plug a hole.

I think that's a compilation of bad timing and the base injection quantity being out. Get it timed properly and go from there.

Thanks all

I have booked it in on Friday, so will communicate the outcome.

Kind regards

Peter

How did you get on?

Progress report
 

The car went in on Friday and had the timing checked, as per recommendation. It was beyond what could be adjusted, so it was concluded that the way forward was a new set of belts, tensioners, etc and a disassembly to see whether anything was visibly worn or required further investigation. Pretty much the advice stated on here.
Its a garage I've used before to deal with complicated stuff.

I have pondered what to do for quite a while. It was a difficult decision 80k miles ago when it was last done, but it seems prices for 850s are on the rise as well as quality of newer cars on the fall. The deal clincher was when we had a family vote on it, and decided to get it back to prime condition. Diesels don't seem to be a popular choice these days, and passers-by hold their clothes over their mouths and look disapprovingly.

The garage was familiar with the engine and have two other customers with an 850Tdi, so that was reassuring. He is getting back with a price, but can't do it for a couple of weeks. In the meantime, I've decided to rest it in case it gets worse, leaves me stranded or completed dies. I drive round in a Cartlon 2.6 Diplomat in the summer, so no problems there.

A new harmonic balancer/crank pulley is also required. I guess this is going to be expensive, but DIY is not an option as I'm snowed under at work until Christmas.