Clicking sound...

[bostonbruins34]

I finally got my check engine codes figured out and have to put some miles on it before inspection so I took it out on the highway for a run. I just had hi-flow cats and 4 new oxygen sensors installed. I just got the car which has 151K miles. Don't know if a previous owner did any work to engine or tranny. The motor sounds great with no clicking, knocking, tapping, etc. While I had it out I cranked it up a few times and noticed if I was going about 70 and floored it there was a hesitation at 100. It was almost like a rev-limiter kicked in. If I eased into the throttle it didn't happen. I slowed her down and noticed a small ticking sound when I got it down to about 40. It wasn't loud and almost sounded like an exhaust leak. Got it home and at idle I don't hear a sound. I'm going to try the rubber hose sound test later today but what do you guys think? Could it be an exhaust leak from the just installed cats or could one of the o2 sensors come a little bit loose? Hopefully it is not something else. I noticed the hesitation before but no ticking before I did the work to it.

[35th-ANV-SS]

It's really hard to determine this sort of thing from a description without actually hearing it. If you can, you might want to try to post a video of the sound.

Ticking could certainly be an exhaust leak though. Ticking could also be a loose spark plug or even a bent push rod.

You didn't over-rev it or anything did you?

[bostonbruins34]

Didn't over-rev it. I don't hear it while parked and even when I rev it in the driveway with the hood up I don't hear it. Only when I'm driving and it gets around 2500-3000 rpm and higher. I only hear it under harder acceleration. Driving it slower I don't hear it. If I step on the gas and bringit up to speed quickly and then feather the gas to keep it up to speed I stop hearing it. When I put the o2 sensors on it I forgot to put on the copper thread sealant that came with them. I'm wondering it is is just a leak? The AIR codes I thought I cleared up came back (P0412, P0418) and maybe the air is leaking back up the air tubes? I have no idea how the AIR system works so I don't even know if that is possible...