Issue with my 2000 s. Misfire bank 2 and loss of power

[Vale]

Hello everyone,

This is my first post, I live in London UK and I am the proud owner of a 986 3.2 year 2000.

I am hoping I can find some help in diagnosing the issues in my car, I will make the long story as short as possible;

It all started with some minor misfires when cold, mainly on low rpm/idle, at the beginning I could only feel them, then after a week the CEL came on. The misfires increased until I started to even feel some very rate stutter and hesitation at around 4000rpm. Other than that the engine pulled like a train, no issues.

Immediately blamed coils and spark plugs, and as I had a track day coming soon, I decided to replace all 6 of them. That didn't fix the issue, but I decided to go and enjoy the track day since high rpm was fine.

First 3 laps (rainy day so definitely not pushing it) all was good but the stutter/hesitation at high rpm was more frequent, then some more laps and the disaster began; idle was the same, but now the issue was that above 3000rpm the engine started to stutter and hesitate, almost like the engine would cut off every 2/3 seconds till 6000rpm where it wouldn't go any higher and even struggled to get there.

Needless to say I drove back home, and after about 60 miles at below 3000rpm, I tried to floor it, and power delivery was fine, back full power no hesitation.

Errors displayed:

P0300
P0304
P0305
P0306
P0154
P1119
P1128

Lambda reading

Bank 1 shuffle quickly between 0.1 and 1, as it should
Bank 2 slowly going from 0.55 to 0.85, even tried to make the car coast and the bank 2 wouldn't go lower than 0.5

Fuel trims

Bank 1 lt -0.8 st -3 fluctuating with rpm
Bank 2 lt 0 st 0 both fixed didn't move

Cam deviation I can only check bank 1 (5.4 degree) , uk version doesn't have the reading for bank 2

I tested the variocam solenoids with the scanner, and for both banks I have had a very similar reaction, which was an even worse idle.

For now I am trying to rule out an o2 sensor failure before I start looking into camshafts timing. What I find odd is that the issue almost comes and goes and seems to change with temperature, I thought if it was bad cam timing I would always have the issue and it would be more consistent.

So I am now trying to swap the o2 sensors, needless to say is a pain, and I couldn't take one off yet, but today I tried to start the engine with bank 2 o2 sensor disconnected, it was almost like the engine was running better, definitely not worse.

What do you experts think? Can this really be a bad o2 sensor?

Thanks to all who will answer

[theiceman]

id stick with your cam timing theory and forget the sensors for now..

[Vale]

Originally Posted by theiceman

id stick with your cam timing theory and forget the sensors for now..

Thanks for replying.

Why do you think the issue is the cam timing?

[theiceman]

Originally Posted by Vale

Thanks for replying.

Why do you think the issue is the cam timing?

only because everything is on the same bank ... ( cylinder 4,5,6 )

each cylinder has its own injector, , coil and plug. so it has to be something common to that whole side..

first thing that comes to mind for me is timing and maybe cam sensor on that side .. which in essence is part of the timing system.

so figured it is a good place to start if nothing else ..

[Vale]

Originally Posted by theiceman

only because everything is on the same bank ... ( cylinder 4,5,6 )

each cylinder has its own injector, , coil and plug. so it has to be something common to that whole side..

first thing that comes to mind for me is timing and maybe cam sensor on that side .. which in essence is part of the timing system.

so figured it is a good place to start if nothing else ..

Yes I agree, what I don't understand is why I have o2 sensors codes and the o2 sensor is not coherent with its reading.

Regarding the timing, the only reason why I am not 100% on it is because I don't hear any rattling whatsoever, and I couldn't think of any other reason why it could go out of time if not for one of those plastic pipes being disintegrated. Ims bearing maybe? If the play was so great to move the timing I would at least see some oil lena or at the very least feel something when the engine is on, this thing, when it runs, is smooth like butter!

I have decided I am going to destroy the old o2 sensor, put a bolt remover onto it and pop a new one on, see if it improves at all!

Can

[theiceman]

Originally Posted by Vale

Yes I agree, what I don't understand is why I have o2 sensors codes and the o2 sensor is not coherent with its reading.

Regarding the timing, the only reason why I am not 100% on it is because I don't hear any rattling whatsoever, and I couldn't think of any other reason why it could go out of time if not for one of those plastic pipes being disintegrated. Ims bearing maybe? If the play was so great to move the timing I would at least see some oil lena or at the very least feel something when the engine is on, this thing, when it runs, is smooth like butter!

I have decided I am going to destroy the old o2 sensor, put a bolt remover onto it and pop a new one on, see if it improves at all!

Can

If you are getting an incomplete burn due to misfires you are going to trip O2 codes for sure. But having said that the front o2 sensor does have responsibility on input on that side of the engine . so maybe it is telling the car to lean out that side maybe ?

Sounds like a great place to start and O2 sensors can be considered Preventative maintenance anyway .