Catalytic converters blocked or Vanos?

[Ben123]

Hi All, wanted to get an opinion on my E60 525i. Recently bought and has been well cared for, but clearly has a problem with either the front cats or Vanos system. Initially the car bogs down under acceleration and frequently goes into limp home mode.. My mechanic has checked the Vanos system, replaced cam sensors and MAF.. which has had no bearing on the problem.. I have contacted the previous owner who has since told me that he had new plugs, 2 coils replaced and the vanos system serviced.. He said his mechanic had cleaned the cats out and was surprised that there was now a problem.. 

Skip forward a couple of weeks, the car is undrivable with the Vanos system connected and with it disconnected its just slow.. 

All the indicators are pointing to the clogged front cats, but can they really cause that much problem.. It idles fine but any sort of acceleration with the vanos connected it bogs down immediately.

any thoughts? 

 

 

[Greydog]

Hi Ben

Welcome to the Forum

In answer to both your posts yes Cats can clog quite easily especially if oil or another contaminant has got into them. Question do you hear a hissing if you turn off the engine? Does the car burn/loose oil with out apparent leaks? Wonder why his mechanic needed to clean the cats?

An alternative could be aftermarket cat's a good exhaust specialist should be able fit them. When I tuned my Volvo T5's I used to fit a 3" downpipe and 300 cell cat to let the engine breath out when power was above 350hp. Cost wont be as much as you think

Dave