Misfires - 986 Forum - The Community for Porsche Boxster & Cayman Owners

boxpriest · 04-11-2017, 10:22 AM

The entire left bank misfires & the car runs rough. O2 replaced, MAF cleaned, new coils etc, no effects. All fuel injectors seem to be working ok (did a hearing test)

Any ideas? And does anyone know what "Oxygen sensor heater" exactly is?

Luccia at Pelican Parts · 04-12-2017, 07:36 AM

Hello Konstantin - If you don't figure it out we do have techs that answer questions on our tech articles. Go here: Porsche Boxster Spark Plugs and Coils Replacement - 986 / 987 (1997-08) - Pelican Parts Technical Article and post your issue with this image in the comment box. One of our specialist will come in with some advice for you. Good luck!

Timco · 04-12-2017, 07:46 AM

The O2 sensors have a sensor and a heater. There's 4 wires to each. Fuse?

Gelbster · 04-12-2017, 08:00 AM

The first thing to check is that you fitted the correct parts. Both the plugs and coils are different in different engine size/year. Some differ by just 1 digit !
Next the connectors on the coils. Unless you lubricate the cover/sheath and push it back to make the connector 'click' into place - that may be an issue.If you don't do this you may have poor connection at the coil and you will swear it is perfect.It isn't.
If you mean Bank 2 (left?? that will be confusing) check the wiring harness. Almost impossible because of the congestion - but use a small ,powerful LED Inspection Lamp. You are looking for rat droppings and maybe loose ground by Cyl #4(brown conductors on a stud).
Next stage is the flailing - swap #4 plug and coil with #1 - does the problem follow? Suggest you find the dwg of the Bank/Cylinder layout to make the diagnostics unambiguous.Using Left/right ,front/back will lead you up the garden path.It really confuses the 996 guys.
Good Luck !

Deserion · 04-12-2017, 09:35 AM

Also make sure the coil packs are seated fully on the plugs, and that the wiring harness connectors are firmly locked on. I had a misfire a few years ago when I did spark plugs, and turns out I didn't seat a wiring connector and thought I had bigger problems.

boxpriest · 04-12-2017, 10:30 AM

thanks for these suggestions, will check it. Well, I'm not sure what the bank number this is, but what I mean is the bank with cylinders 4-5-6 as on this drawing:

Jamesp · 04-12-2017, 06:26 PM

Quote:

Originally Posted by boxpriest

thanks for these suggestions, will check it. Well, I'm not sure what the bank number this is, but what I mean is the bank with cylinders 4-5-6 as on this drawing:

Bank 1 has cylinders 1,2,3

Bank 2 has cylinders 4,5,6