I've got an h22 on crome that recently started giving me an odd oscillating sound whenever it's at idle. This is not a vaccum leak like most of you would probably think because the RPM does not change but the engine's tone changes, it seems to go up and down but the motor and a/f is steady.

Trying to bounce some ideas off you all because i'm stumped...

 

do you have a wideband? sounds like its running lean.

 

An oscillation can be felt by the slowing of the crankshaft due to the inefficiency of a combustion event or misfire. Some setups will misfire earlier then others in terms of AFR, but it depends on your setup. Some engines don't like to run as lean at idle... what is our idle AFR and specs on your setup?

 

yeah, wideband reads "normal" for my car, 14-15 at idle... i've never had this problem before and it has become more prevalent as of late. I am going to try to richen the mixture and see if that helps.

 

I looked at it last night and the behavior is the same... i did drive around to check for it before making any changes and it does appear to lean out a bit when it starts behaving that way.

I'm not sure what could be causing this... could a bad o2 sensor be the issue?