Turbodiesel "misfire" When Cold.

[Guest Mike P]

I'm being a bit cheeky ;) as this is my first post, but must admit I have never come across this before.

 

Setting the scene:

• N reg ZX turbodiesel with 149000 miles on clock.
  
• Was running on biodiesel 80% in summer - no problems at all
  
• Changed oil, fuel and air filters about 1000 miles ago - still fine
  
• Very recently, it has developed a sort of misfire at low revs when cold, and when heavily loaded.
  
• I filled it with DERV last couple of fills, but no different.
  

It is fine when engine is hot, but have to keep it above, say, 1500 RPM when it is cold, though it idles perfectly and starts instantly. Every time it misses, you get a puff of smoke from the exhaust.

If it was a petrol engine, I'd say it had a weak mixture.

 

Has anyone any ideas? I'm somewhat baffled!

 

Mike

[Guest Colin Hunter]

Hi Mike.

 

When you say "Biodiesel" do you actually mean Veg oil? It's possible that the injector pintles have become sticky with deposits from the "alternative fuel" and one or more of them are not atomising properly. Try a dose or two of injector cleaner through the system with straight derv and see if that cures it. If it doesn't, you may need to replace the injectors with some recon or good 2nd hand ones. The "Smoke you see when the engine misfires will actually be a puff of unburnt fuel from the dodgy cylinder.

 

Cheers. Hope this helps. ;)