My 2003 avensis verso wagon is shuddering while idling.
It has trouble gaining speed and shudders intermittently while driving.
Its probably a fuel problem, but mechanic wants $2000+ to change o2 sensors.
So i will do myself
Possibly that will alleviate the problem, but more possibly not. However, sensors may help determine problem .
My question is ..there are 4 sensors ..two above cylinder 2 and 3 , i'm led to believe...and two below ( 1 and 4)
Internet suggests post CAT and Pre Cat sensors.
I assume upper sensors are pre cat.
But post Cat? Below. ? Is that correct? And just where is the Catalytic converter located? I thought it was just before muffler. But no sensors under car that i can see. Any help with knowledge is appreciated. Expensive even to install myself . Car is only worth $4000 max. So spending $2000 for mechanic only to find more problem ( fuel filter?) Really hurts