Knock Limit

[ianw]

hi i have a 2002 tdci and it keeps getting a fault where glow plug light flashers .so off to the garage

it goes for the 2nd time and they say it is a knock limit exceeded so they recode it at £102 .but it has been a diffrent injector each time does anyone no why this happens or how it can be stopped

[mintalkin]

it could be that the injectors are starting to wear, the above knock threshold code can sometimes be cured by recoding,i would get a leak off test done and that will comfirm any dodgy injectors,also with your car is pre 2004 make sure the correct code reader is used as the recode price thay charge is a bit over the top,and remember the recode from the lable is done in firing order not physical.

[FOCA]

Garages love to spend your money, next thing they will be getting you to buy a new set of injectors, before you know it you will have spent more than the car is worth.

injectors can cause "knock" (detonation/ pre ignition) but other things can cause it too - a "lean" mixture, or a build up of carbon (due to too rich a mixture) a clogged exhaust/ cat too much boost, the dreaded EGR system etc etc

A good service, (including air filter, fuel filter, oil+filter) and the things that SHOULD be on the service shedule (cleaning out the inlet manifold from the gunk the EGR has deposited, blanking the EGR valve to stop it happening again)

the intercooler is probably full of oil and the cat is probably choked,

Do you know if it is a fixed vane or variable vane turbo? is it a front or rear mounted EGR?

is the car driven hard?

[ianw]

hi thanks for all info i am not red hot on car bits but i do no that the egr is at the front and wsa cleaned by

the rac man .and i dont no what you mean by fixed vane or variable vane and no the car is not driven hard i tow a caravan

about 2-3 times a year thanks