I have a 2007 with 113k miles on it and I bought it used and and after driving it for 300 miles I got a p0420 code and a rough idle. It recently started doing the rough idle about 500 miles after and when I'm in neutral the rpm would jump to 1500 and go down to 800 then back to normal idle. I can feel the engine shake while it happens. I dont know what has been done to it before but on the carfax it only shows oil changes and state inspection. I did replace my spark plugs recently and the ones on there previously were hand loose.. everything else looks stock.

I did put cata clean to help with the p0420 code and from what i have been reading it seems like a catalyic convertor problem. I was thinking of going test pipe but i have read that people still get the code p0420 with that. Also after the cata clean i was able to go 400 miles before it turned on again.

Anyone have any previous experiences with the weird idle issue ?

 

Also i dont know if this is normal or not but when say I'm in 4th gear going 35mph then I let off then accelerate again, it jerks when I hit the gas pedal..

 

How tight did you tighten the spark plugs?

 

As soon as it got tight, I did a little more than half a turn. I didnt have my torque wrench with me. I'd imagine it would have ran rough with the previous spark plugs due to not being tight.

 

Needs a new cat. Berk HFC didn't throw a code for me on my 2006 when I ran it on the stock ecu

 

I have not. How do I do that ?