Bad MPG and no idle!!?!

[Blimey 0]

Alright lads,

 

With my limited knowledge of anything other than an "a" series engine I have a question about Catalytic converters.

 

If your cat is knackered would it effect your idle revs (i.e no idel revs at all) when the engine is warm and also give you a terrible mpg?

 

I ask because a guy down the local VW stealers told me this was the case and I don't believe him... been bitten before by VW mechanics..

 

Cheers

[Jim 2]

Doesn't sound likely to me.. it sounds more likely to be a fault with the lambda sensor which, I believe, sits in the exhaust system just behind or before the catalyst. A faulty lambda would make your engine run badly and give you poor fuel economy.

[exturbo2003 0]

they both will

if you start your engine when warm and still ticking over see if you have a good airflow out the exhaust pipe, if itslow you have a blockage. when it dies undo the joint in front of the cat so its loose and restart. if it now runs fine (though noisey) try the next joint and so on till you find the blockage, though it probably is the cat.

do you have a voltmeter, if so measure the voltage on the single wire at the lamnba probe plug, 4 together and 1 single, voltage should be between .1 & .9v constanly changing. rev up and should change rapidly and if it doesnt all is slow it needs changing

[Blimey 0]

Thanks for thw advice guys, I'll give 'em a go and let ya know :)