I have an 03 plate 1.9 TDi Octavia that I use as a taxi. The car has done 130,000 miles and is regularly serviced.

I have had the engine blow on me at 100,000 miles. The symptoms right before failure was for the engine to rev to full revs before the engine went bang..... Investigations showed that the the turbo checked out ok. No answers were found as to the cause of the failure.

A reconditioned engine was fitted and everything was ok.

Recently, the engine was running a little "lumpy" at idle. Using a diagnostic machine, the manifold air regulator valve was found to be faulty. A new valve was fitted and the car was taken for a test run. After only a few minutes, the engined went to full revs before blowing up......

A bit of a mess. Again, the turbo was favourite, but on strip-down the bearings and turbine blades were fine. A little oil residue was found in the pipework, but nothing that looked out of the ordinary.

Investigations are still on-going as to the cause of this second failure. I don't want to go through the expense of fitting another engine until I am sure that the root cause has been found.

Could this be a fuelling problem were the engine management system thinks that engine needs more fuel? Could the replacement manifold valve be a coincidence seeing as the failure also happened with the original valve fitted? Why didn't the rev limiter stop the engine over revving?

All these questions. I would appreciate it if any one could help with the diagnosis of this problem. Has anyone had this happen to them and if so what was the reason for the failure?

Thanks for your help.

Gary B

Sounds almost certainly like run on or over run often caused by unburnt fuel in the induction system.

There is an anti run on device (Intake Manifold Flap) on the PD engines, is yours a PD?

This is all tied in with the EGR which are known to get coked up and in veiw of the miles you've covered probably will be. Was this replaced when the new ingine was fitted? I doubt as it's all connected on the intake pipework.

When your engines have 'blown' have you read off the fault codes.

Just reading your post again you say you have replaced a manifild air regulator valve - can you be more specific?

The Manifold Air Flap that I mention is controlled by Change Over Valve N239 which uses vacuum to operate the flap.