frontera 2.2 16v petrol ecotec , running prob, hunting tick over

[Toppo]

hi got a 2.2 W-REG  petrol , and it runs ok ,, but the tick over  is lumpy some times , ive cleaned and checked the pipe work , cleand throttle body , still no joy , im going to check the cam belt timing ,  but i cannot see the crank pully wheel timing mark .. auto data says its at the bottom , but cannot see it ,, can some one help me out , also reading other posts it says it could be the crank shaft sensor ,, also i think the cat is not to good , can i buy pass the cat some how ,     cheers mark

[666]

If its hunting i would suspect the idle control valve or the maff sensor

[Toppo]

ive tyred cleaning the idle valve , but still the same,  wat one is the maff sensor ,, another thing i noticed is that the plugs keep going black sooty ,, running rich ????  any ideas  thanks mark

[666]

Maff is the mass air flow sensor in the air intake pipe.

Im not too clued up on the 2.2s but if you ask here they might be able to help more than me  ;)

[dxmedia]

sooting up sounds like lambda

[Toppo]

sorted it today  after checking things,,  i found the cambelt  timing one tooth out on the right cam >?   runs ok now , also welded the manifold up ,,    thanks for all ur help  cheers mark