Hi ya'll, I am new to the forum.
I have been trying to fix a reacurring po420 , p0300 code , just insalled down stream O2 sensor. was going to install the upstream sensor too but the one they sent me turned out to be used and I am returning it. While test driving i noticed that it really cuts out badly on bumpy roads and now the tach stopped working. The tach problem happened not long ago and I fix
ed it with a new crank shaft position sensor and that cleared the PO300. The way it is cutting out on bumps suggest a short in a wire some where,
thanks , TJ