OK, I’m stumped and several mechanics are stumped. Any thoughts at all would be a great help.
My 89 CRX was required to pass a CA smog check. I took it in and it passed 5 out of 6 parameters. The 6th was NOX at 25mph. So I took it to a place that the state deems capable of fixing and rechecking it. About $600 later it passed. I was told they found the EGR passages clogged so they removed the intake manifold to clean it. They also found a “lazy” O2 sensor and that was replaced. After that the NOX readings were significantly lower, the CO about the same, and the HC actually measured slightly higher but well within limits (below average). Good to go!
Except… After I got my car back it would idle extremely rough at stop lights for the first week or so. And I noticed that I could smell exhaust in the cabin. With the windows up and the blower on with outside air selected I could smell exhaust. It goes away immediately if I turn the air on recirculate. With the windows down I also notice it, but definitely worse with the fan on and outside air selected.
I took it back to the smog shop and they were unable to find anything and didn’t really notice it. When I checked I could tell a major difference between having the hood open (barely any comes in to the cabin) and the hood closed (smog city). They don’t think it has anything to do with them.
I took it to my long time trusted shop and they took a look. They can smell it. They replaced the O2 sensor again (smog shop installed a “cheap” one and my shop put in an OEM). They also tried replacing the thermostat as the old one kept the temp a little low. PCV valve was also replaced. They checked the exhaust manifold and there doesn’t appear to be any leaks. No vacuum leaks were found. The problem is still there.
My shop took another look at it over a couple of days and was unable to find anything that is causing this. I’m at wits end. My shop suggests maybe consider a new catalytic converter but even then my smog numbers are just fine and the exhaust out the tailpipe doesn’t really smell as potent as what’s coming in through my vents.
Any suggestions as to where to go from here?