Hi, I hope things have cleared up for you without too much intervention.
Just before Christmas my nightmare began, let me tell you my story about by 55 plate IS220D!
Driving to work one day, engine warning light, check VSC and the traction control lights came on and the car went in to limp mode. Got to work, called Lexus who said to take it in and called the AA. AA did diagnostics and said the problem reported was the particle filter. His normal suggestion would be to give it a long hard blast on the motorway but did not want to suggest doing this as there was a chance that it could cause more problems and cost more to fix. Instead it should be taken to Lexus who can clear the filter without having to race the engine. Took it to a Lexus dealership who quoted me just over £1000 for a new cat (not much diagnosis), got a phone call with a revision telling me that there was clearly something else that caused the problem and it would cost me £1200 to have the engine stripped to investigate. On top of that, there would be the fix and then another £1200 to put it together again. I was now faced with a bill of £4000 inc vat with no assurance that they would be able to find what was wrong in the first place.
The good news for you could be that Lexus said they were confident that they could get Lexus UK to fund the full cost of the repair, my luck ran as it missed a lexus service and the goodwill ran out.
I got the car dragged to a garage in Essex for a strip and clean and a new cat. Total cost was £3700 inc VAT. Engine was full of soot and grime which needed to be cleared and the cat was shoot.
Car is back now and I need to have 2 services 500 miles apart and not drive over 70mph as a precaution. On Friday I have the final service and then it should be back to normal. All in its probably cost me over £4200 including rebuild, cat, hire car, servicing, etc. Garage have told me to do the following to help avoid it happening again:
* Use fuel with detergents (or Wynns 'Supremium' fuel additive (about £5 for a bottle that does 5 fills))
* Add a cleaning additive to the fuel every 5000 miles (I have chosen to use "Wynns Diesel System Treatment", seems to be quite comprehensive)
* Increase oil changes (I will stick to the 10k garage services but also add a home drain and fill between services)
* Use fully synthetic oil (service manual says to use semi synthetic but apparently this is a now brainer)
* Try to keep the Revs over 2k, I used to drive 100 miles on the motorway per day and was in 6th gear for most of it barely doing 1500 rpm which does not get the particle filter hot enough to burn.
* Every month or so, drive over 3000 rpm for about 10/15 mins to help burn the soot out.
I had two hire cars whilst my Lexus was being fixed, reading the manual when the particle filter starts to get full, it automatically increases the revs and burns it for you as a precautionary measure (Saab 93 and Vauchall Insignia). The first thing you notice in the lexus is limp home mode, the second thing you notice is £4200 being extracted out your bank account.
Hope this is of use to you and anyone else that has similar problems in the future. Let me know if you need the garage in essex that sorted me out and avoid any engine reconditions around the Heathrow area.
Stuart