Today as I was checking my car I found out that between 1k and 2k rpms it moves up and down at a steady pace but only in park or neutral.I have a SEL code P0420 would this cause the rpms to go up and down or is it something else?

 

P0420 Catalyst Efficency Below Threshold (Bank One)
thats caused by either a bad cat or 02 sensor

the throttle issue is probably unrelated...you may need to do the relearn procedures. i had the problem and had to replace the TB.

 

What is a TB?

 

TB = Throttle Body...thats just short hand

 

Possible Causes

1. Improper warm-up of three way catalyst
2. Exhaust tube blockage or leak
3. Intake air leaks
4. Injectors
5. Injector leaks
6. Spark plug
7. Improper ignition timing

The ECM monitors the switching frequency ratio of front and rear heated oxygen sensors. A warm-up of the three way catalyst with high oxygen storage capacity will indicate a low switching frequency of rear heated oxygen sensor. As oxygen storage capacity decreases, the rear heated oxygen sensor switching frequency will increase. When the frequency ratio of front and rear heated oxygen sensors approaches a specified limit value, the warm-up of the three way catalyst malfunction is diagnosed. Malfunction is detected when warm-up of the three way catalyst does not operate properly, warm-up of the three way catalyst does not have enough oxygen storage capacity.