P303, P1315 And Rough Idle After Warm 1-2K Rpm

[mkesler]

Any help would be much appreciated! I have been dealing with a cel P303 and P1315, I have changed all the plugs replaced the cylinder 3 coil and no difference. After I replaced all the plugs now I get a high pitch chirp from the drive side engine area at low rpm. I seem to get the P303 every spring after my 99 986 is stored for the winter, a little moisture i assume and usually goes away no problem. This year.... no luck IT runs fine for 30 minutes or so then get the blinking cel and sluggish in 1st and second gear? Possible the AOS is bad? Please Help!

[Wayne R. Dempsey]

A blinking light is bad - the engine should be shut off immediately if you see that, as it can damage the catalytic converters. I don't have my reference manual in front of me, what are the two codes in the book?

-Wayne

[RFM]

Both codes refer to cyl. #3 issue, i would check that out first. Misfire detection covers more than some bad plugs/coils/wiring's, do a compression and/or cylinder leak test, an exhaust gas test (HC/CO/CO²/O²) is also very useful.