Tip for 986 owners with Bucking & Misfire issues
 

Well about 1 year ago I had replaced the o2 sensor ahead of the Passenger Cat (Engine Bank 1) cause i was getting a p-code indicating that this sensor was faulty. From then on (which i didnt realize right away) my 1997 Boxster suffered from low RPM bucking and Pcodes indicating component of my Secondary Air-Injection system was faulty as well.

About a week ago i started to get the dreeded Flashing CEL, and since Danger is my middle name I gave the engine afew rev's and the flashing stopped. I then hooked her up to my SnapOn Solus ODBII scanner and I had 4 Pcodes:
P0300 (Multiple Cylindar Missfire) vauge, i know but then that was followed by...
P0304 (Missfire Cylindar 4)
P0305 (Missfire Cylindar 5)
P0306 (Missfire Cylindar 6) So these clearly told me the entire 2nd bank of my engine is either running a fuel mixture thats way off or that I have some sort of Ignition problem.

THEN, i noticed since I last updated the software on my ODBII scanner that there is a new section to look up Previous DTC's which i dont know what DTC stands for but it apparently displays the Pcodes that trigger from my last drive but cleared themselves for whatever reason. So I look and BAM, Theres P0150 listed in there which is (O2 sensor ahead of Cats. Bank 2)... So with that in mind I concluded that the o2 sensor is one of the only devices on the car that can affect 1 entire bank of the engine simultaneously.

So I went ahead and ordered a Bosch o2 from Worldpac and installed that sucker, reset the ECU then started her up, driver her around noticed that i had eliminated the bucking and the acceleration was so much smoother, Even this morning it felt great. I haven't done the OBC hack yet so i wont be able to report any increase or decrease in Mileage but i can report that the CEL doesnt flash, and i no longer get the P0300, P0304, P0305 & P0306 anymore.

So that concludes my TIP, makes sense right? A whole bank of cylindars misfiring at the same time and the only sensor that single handedly desides what the A/F ratio should be for an entire bank of cylindars points right to the O2 sensor for that side of the engine...

I think the problem with diagnosing this with standard ODBII scanners like $300 dollar ebay ones is they wont show you the hidden Pcodes which make it a hell of alot more difficult and costly to hunt down the underlining issue with ones vehicle.

Any questions?

P.S. One point i forgot to point out, If you replace 1 O2 sensor and not the other, you will eventually have problems with 1 bank of your engine recieving a different A/F mixture than the other bank of the engine.

Nice info there CJ! That's interesting that it ended up just being the O2 sensor. I think I read on renntech awhile back that misfires on an entire bank points to a solenoid issue....I guess the difference here was that you had a saved P-code that turned on and off on it's own and that it showed an O2 sensor problem. Something to definitely think about.

Thanks for the headsup! :cheers:

I think you've only hit on one of the reasons an entire Bank can have an issue.

Swapping the O² sensor would not fix them all - such as a Knock Sensor or Variocam issue - these too would cause drivability problems from a single bank.