[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