2001 v70 engine shudders at part throttle

[ironhead]

hi all ,
I have a 01 v70 n/a and when throttle is depressed hot or cold about 20 % the engine shudders. If the pedal is pressed harder it stops or if you lift it stops but it only shudders when accelerating. It has set no codes except one for low catalytic efficiency. any help greatly appreciated.

[draser]

I'd look at maf and % engine load signals with a code reader at idle and 1500 rpm to determine if cat is actually plugged up. There was a recent post on how to test O2 sensors for a 0420 code. Same post had waveforms for front/rear sensors detailing how rear sensor should switch 2sec or more slower than front for a good working cat.

[SuperHerman]

I would look at MAF and the throttle body. I just rebuild my throttle body with the Sacer kit and my hesitations went away. The original throttle body was replaced once, long ago under warranty. Time consuming but not complicated. Many posts on it.