Hey gurus: Need help with engine problem
99 323i auto, M52TUB25
Just got done replacing head gasket due to coolant leak. While off, replaced basically all vacuum hoses, everything looks good. Checked function and condition of DISA valve, checks out perfectly.
On startup, received codes for minor emissions control leak (pre-existing) slow response on one Bank 1 o2, no response on the other Bank 1 o2, and Seconday Air injection Bank 1 flow to low.
Also more critically, misfire on cylinder 4, and code 1250 which I *think* is Fuel Pressure Regulator Control Circuit malfunction.
We moved the plug and coil from 4 to another cylinder, code did not move, still runs like crap. Replaced the suspect plug, same thing.
We replaced the FPR and (ancient looking) fuel filter, and all fuel lines and vacuum lines associated with those. Started right up, runs like complete crap. Only code coming up now is the 304 -- misfire on cylinder 4.
We are 100% dead sure the primary timing is right. Ran it around 3 times by hand and observed the workings. 99.5% sure the VANOS is built back up correctly too.
Running out of ideas, any gurus want to wade into this one? I'm desperate for ideas...