So I have been living with CEL P0173 since purchasing my M3W about a year ago.
When I got the car it had a Kuryakyn air cleaner that did not have the necessary little 'ears' that attach to the cylinder heads for support. So I removed the Kuryakyn and installed a S&S Stealth air cleaner that has the proper supports.
The car ran reasonably well with either air cleaner and with the S&S air cleaner P0173 even disappeared for a number of months, only to reappear, then disappear, etc. As others have said here one of the major culprits of P0173 are air leaks at the intake gaskets. I figured that Kuryakyn air cleaner had beat up the rear cylinder intake gasket.
So this last week I replaced the intake gaskets. The rear cylinder gasket did look a bit different than the front cylinder so I thought I had found the problem.
Upon test-starting the car after the new gaskets the CEL went away within about 4 restarts. Car ran a bit rough but nice and smooth in gear.
Unfortunately now with maybe 10 miles on the car the CEL is back on..... with my old friend P0173.
So what is my next move?
1) Swap the exhaust sensors side to side to see if the CEL follows the (bad) sensor? Clean the exhaust sensor electrical connections? Replace the rear cylinder sensor?
2) Unwrap the header pipes and check for cracks in the exhaust manifold?
3) Replace the exhaust manifold gaskets?
4) Or ?
Any input would be great. It was a good feeling to have the CEL go out after the new gaskets and I would sure like to find what is causing that code and get the car running in top shape again.
If it matters - the car has a Garage 56 Stage 1 Exhaust in addition to the S&S Stealth air cleaner.
