Smoke from the exhaust on boost

[marojojoem]

Morning All, my 1986 Turbo is producing a fair plume of oil smoke from the exhaust but only when I give it plenty of throttle at high rpm. I have a very bad habit of jumping to quick and expensive conclusions about my particular money pit but I can't get away from the idea that in its 35th year the turbo probably needs some tlc.
This has only started to occur in recent weeks.
I'd welcome any suggestions, particularly those that solve the problem for less than fifty quid.
If I can get the turbo overhauled is it a driveway job to replace?
Thanks as always

 

[PSH]

Hi

Not easy to diagnose from a distance could be a number of things.
Possibilities can be valve seals, turbo, rings, clogged AOS etc. A few more details might narrow the cause, any smoke on start-up after it's been standing a day or two which clears? This could be valve guides. Blue smoke more likely to be rings. Smoke on over run, possible turbo. Is it burning oil, higher than normal comsumption? When was the oil last changed and for what type?
As for Turbo overhaul, yes it can be done on the driveway...cost will probably be around £500 for the work from someone like Turbo Technics or Universal Turbos. Allow for extras like seals/oil etc.

Regards

Pete

 

[TTM]

Can you make out the colour of the smoke?
Hopefully it is only just perfectly black and since you are 100% confident this happens only on full load then it could "only" be worn out valve stem seals. These can be replaced without taking the head off, even if it's a bit of a tedious job.

 

[marojojoem]

Hi thanks for the response. The smoke is grey not black so not sure if this answers your question?

 

[marojojoem]

Pete thanks as ever!
There's no smoke on start up and no smoke on the overrun. Its just during hard acceleration at high boost / rpm.
The oil consumption is a little higher than ideal but in no way excessive.
The oil and filter were changed in November, Millers Classic Sport 20W50

Cheers
Mark

 

[944Turbo]

Pete thanks as ever!
There's no smoke on start up and no smoke on the overrun. Its just during hard acceleration at high boost / rpm.
The oil consumption is a little higher than ideal but in no way excessive.
The oil and filter were changed in November, Millers Classic Sport 20W50

Cheers
Mark

Might be running a bit rich if it is black or grey. If you have a fairly standard setup then a boost leak will allow it to run rich - usual culprits are the vacuum lines, the idle stabiliser, the throttle body, sometimes the intercooler connections and pretty much any rubber in the intake system! (after the turbo)
Tony

 

[PSH]

Hi Mark

Ok, so unlikely to be valve seals or turbo...grey is an unusual colour. It could be very slightly rich or it's the rings.
Another question first...is the 20w50 new to the car or the normal oil that you use. 20w50 is a little thick for these engines, 10W50 or 10w60 is fine. Higher than usual oil consumption would suggest wear and giving off smoke at high RPM is most likely rings
Turbo smoke is usually on over-run or possibly idle. On start up would be valve seals
You could try changing the oil if the new oil is thicker than used before to slightly thinner, Might be best to get a leak down test done, that should help to tell what's going on.
Trouble with these cars is it's not always what you think, some things that look like an expensive fix can at times be a relatively easy problem..

Pete

 

[PSH]

Oh...forgot to add...might be worth checking the AFM...see if there's any wear on the track, this could mess up the fuelling but wouldn't necessarily explain the higher oil consumption.

 

[marojojoem]

Thanks for the various responses thats very very helpful.

I'm thinking then that the most likely culprit is a very rich mixture at high mass flow either because of an air leak or AFM malfunction.
I've had a quick look around and cant see anything obvious by way of a leak although all of that pipework has been off recently so I suppose there might be an issue, maybe even a split intercooler. I'm also thinking that it would need to be a big leak because the A/F ratio would need to be substantially off and surely you would hear something from the driving seat?.

Either way I am going to take the pipework out for a thorough inspection and look at the AFM and clean up the tracks.

Thanks again
Mark

 

[marojojoem]

Oil consumption btw is probably about a litre every 1000 miles I reckon

 

[944Turbo]

If its very rich it will wash out some oil, I was thinking fuel (black smoke) mixed with oil (blue/white smoke) might give you grey. Best way to check for boost leaks is to disconnect pipe from the turbo install a a suitable cap with a tyre valve and use it to pressurise the inlet. Then go around and listen - squirt soapy water and look for bubbles. Common pipe to pop off is the line to the bottom of the throttle body. My ISV on the coupe was leaking really badly and the the throttle body shaft seals nearly always leak - Simon Peckham used to do rebuilt throttle bodies on an exchange basis.
What colour are the plugs - usually a good indicator of what is going on inside the engine.
Fingers crossed for something minor!
Tony

 

[marojojoem]

Thanks Tony
That's given me a pretty good list to work through.
I will get my sleeves rolled up and make a start.
I will post any discoveries
All the best
Mark

 

[marojojoem]

Just to bring this up to date, I had a look inside the AFM and measured the voltage which seemed to rise smoothly from 0.24 to just less than 5V through the full range of deflection of the flap so that seems okay. The box was sealed with some brittle red gasket sealant which I thought might have been the original factory fit so maybe nobody's been inside until now. What does the blob of silver denote on the gearwheel rim? Is that the factory set position and if so should it be aligned with the nut?
Thanks for reading and in anticipation of any thoughts.
Mark

 

[944Turbo]

Just to bring this up to date, I had a look inside the AFM and measured the voltage which seemed to rise smoothly from 0.24 to just less than 5V through the full range of deflection of the flap so that seems okay. The box was sealed with some brittle red gasket sealant which I thought might have been the original factory fit so maybe nobody's been inside until now. What does the blob of silver denote on the gearwheel rim? Is that the factory set position and if so should it be aligned with the nut?
Thanks for reading and in anticipation of any thoughts.
Mark

I think the red sealant and silver dot means someone had been there before, I have had some success with increasing the spring pressure to cure mid range richness, cant use it sort flat out running though.
Tony

 

[marojojoem]

Just to bring this up to date, I had a look inside the AFM and measured the voltage which seemed to rise smoothly from 0.24 to just less than 5V through the full range of deflection of the flap so that seems okay. The box was sealed with some brittle red gasket sealant which I thought might have been the original factory fit so maybe nobody's been inside until now. What does the blob of silver denote on the gearwheel rim? Is that the factory set position and if so should it be aligned with the nut?
Thanks for reading and in anticipation of any thoughts.
Mark

I think the red sealant and silver dot means someone had been there before, I have had some success with increasing the spring pressure to cure mid range richness, cant use it sort flat out running though.
Tony

Tony, maybe you are right it could have been adjusted in the past to make it run richer, the A/F ratio might be a long way out at high mass flows because the curve is non-linear. I'm going to pull a couple of plugs to inspect, any maybe increase the spring tension to lean it off a bit, also check for leaks between turbo and manifold, lets see....

 

[944Turbo]

Once it is fully open (I think 4,500rpm) it switches to the map on the chips, so the spring tension no longer factors, I think the springs weaken over time which is why I have tweaked them slightly to sort issues below 4,500 rpm.
One other thing worth checking - how much oil in the intercooler - they are usually a little bit oily but might be worth cleaning it out and seeing how quickly it fills again - if oil is getting past the turbo seals the IC is good at collecting it.
Tony

 

[marojojoem]

Okay Tony thanks so I can forget the AFM for the problem I've got then. I will investigate the intercooler.
I'm being quoted £185 plus VAT to overhaul the turbo so I might get that done since its not a fortune

 

[Waylander]

185 thats a bargain, dont think I have ever had one rebuilt for less than 300, for any car

 

[marojojoem]

185 thats a bargain, dont think I have ever had one rebuilt for less than 300, for any car

Midland Turbo in Nottingham

 

[Dan944t]

£185 is very cheap! lowest i found almost 2 years back was £450+ so i sent off my shaft for checking and also balancing and bought the kit from same people and rebuilt the entire thing myself for around £50 return postage i think ??

the pain if i’m honest is getting the **** out and back on again espeacially if your bolts are seized as bad as mine were ?? what a bitch that was!

ive also got to take it off again as i want a bigger turbo one day soon ?? silly me, modified the whole engine and kept the same turbo ?? live and learn the hard way .....

good luck ??