richardoh

I need some assistance with my 99 Civic LX with a D16Y7 auto. Ive had the car for a few months and it has been like this the entire time (7-800 miles so far) and its starting to annoy me. It currently has 141,000 miles on the car and drives perfectly fine. I drive roughly 70 miles a day, it gets 30 mpg average and the car has not given me any issues aside from minor oil leaks which I have resolved since. The only two bobbles are it makes this strange knock/ticking noise when accelerating or revving AND P0420 will pop up after driving on the highway.

History regarding what I did to the car/engine:

Seafoam in engine/intake manifold/fuel when car was purchased
Fresh 5W-30 synthetic oil and a Purolator Boss oil filter
Valve cover gasket
Valve adjustment
Timing belt/water pump/tensioner/front main seal and cam seal
Thermostat
New radiator cap
Oil pan gasket
Brakes
Pressure washed engine bay (not sure if this matters but I did it)

After everything I have done it still make the noise and recently I replaced the gasket between the manifold and cat hoping it would fix it as it could'ove been an exhaust leak but no luck. Still makes the same sound and code still pops up when I drive on the highway.

Any ideas or suggestions would be great. I will be posting a video of the noise soon to further display the issue.

TomCat39

Bump after approving thread.

tamboo

https://www.obd-codes.com/p0420