So the data from O2 sensors is here:
Unusual points to mention would be that mV on sensor bank 1 jumps between 100- 800 mV, when bank 2 is consistent at ~400 mV
Trims on O2 sensors are around +-2% at all times
Unfortunately am not qualified to tell if that means anything or if I should gather more data

 

For now we’re interested in graphing the two pre-cat O2 sensors (b1s1 and b2s1)Static data is not useful. The sensor behind the cat should read a relatively steady voltage between .5 and .7 V. You should have something like this depending on the time scale (x axis).




George

 

After reading all the posts I think I would go back to basics . Fix the easy stuff , the arcing coil wire and the MAP sensor gasket leak first before going any further . They both are simple fixes . Replace the gasket for MAP sensor and clean coil posts ( if it’s been arcing it probably is carbon tracking which is conductive ) and replace coil wire or at least clean coil posts and put some silicone grease inside coil wire boots to try to stop the arcing.
Any arcing is causing misfires ,to some degree , as there is voltage producing the arcing to ground and that voltage is Not getting to the spark plugs to produce spark as it should . All the voltage produced by the coil is designed to end up at the plug to produce a hot quick spark . Any voltage lost and the spark is weaker than it should be or fires slightly late .
The misfire codes are generally generated when the crank position sensor senses that the crank has momentarily slowed down or not appropriately sped up when a cylinder was supposed to fire . Comparing with the cam sensor tells it which cylinder . It takes several sequences to set code . A weaker than normal spark could cause this erratically . The weak spark would also cause unburnt fuel out exhaust which the O2 sensor sees and ECM then try’s to adjust fuel mix for that bank causing other cylinders to misfire until all settles down

And if MAP sensor gasket isn’t sealing then you for sure had a vacuum leak there at the manifold .

At higher rpm the misfires may not be noticeable or present because the cylinders are firing faster and a little voltage loss may not affect spark as much depending on engine load . But after high rpm then quickly idle you would notice prominently as ECM tries to adjust fuel and spark with the assumption that coil voltage is good when it’s not (with some voltage being lost in arcing )and recover to maintain rpm
A combination of map sensor leaking causing wrong manifold pressure readings and vacuum leak plus misfires could cause just what you describe . I think The other data , like fuel trims and sensor readings will be misleading or off until vacuum and spark is corrected. Diagnostic flowcharts typically start with checking and eliminating basic air , fuel, spark issues first then getting into fuel trims , O2 readings , etc.

Just another thought, might be a long shot but are you sure the metallic clacking sound isn’t the sound of the arcing it can sound like that if it’s not loud. Or more likely just the sound of cylinders working against themselves misfiring maybe .

 

Hey guys, some updates here
Shout to George, I have tested all O2 sensors and there are 3 of em, sensor 1 bank 1 (before cat), sensor 1 bank 2 (before cat) and s 2 b 1 (after cat)
Interesting observation is that voltage from sensor 2 bank 1 is jumping between 0.1 - 0.8, which is incorrect behaviour, it should be consistent ~0.4

It is a direct sign of partly clogged or broken inside cat (I have checked O2 sensor, it's fully functional and fine), anyway, it says that the exhaust gases are not cleaned up after going through the cat
As an addition, this clanging metal noise is going somewhere around cat spots, which might be a sign of broken ceramic pieces inside the cat
Plus, I did notice that my exhaust has a very prominent gas smell, which also looks like a not-working cat to me

A partly clogged cat might explain the MAP pressure going down when throttle, cause a clogged cat creates back pressure, and all that also causes misfires

It might also explain a long term fuel trim being on 20%+
ECU thinks that there is enough air in the air supply → fuel supply is normal.
But in fact, there is less oxygen, so the mixture is poor.
O2-sensor senses this and says: “mixture is poor”.
ECU starts adding fuel to bring the mixture up to normal → LTFT goes to plus (e.g. +20%).

I dont have a garage/place or finances to replace the cat, but I will try to diagnose it a bit deeper and keep you updated
But it surely looks like a cat problem to me

 

The rear o2 sensor tracking the front sensors does suggest a failed cat. Exhaust back pressure testing will confirm if it’s also blocked. Oil, coolant or a rich exhaust can kill a cat so those issues need to be addressed before replacement.


George

 

I'm betting that a bent intake valve has caused clacking rocker, fuel trim to read way positive (lean), and that the resulting severe misfire has destroyed the cat. That would explain all of it including random misfire codes.

Not sure where you are getting your information, but as far as normal O2 sensor voltage on front sensor see post #22. Static values on O2 sensors are less than useful. The front is not supposed to be steady at all (it is only the rear sensor that should be relatively steady). If it is controlling properly, front sensor will swing back and forth from around .1V to .8V, just like shown in the post. A front O2 sensor at a steady voltage is in open loop, and it's reading is not being used at all by the PCM. Rear sensor can be any voltage, but should not be cycling with the froont sensor.

+20 means the PCM has added fuel to the fuel curve in an attempt to cure a too lean condition.

To me the elephant in the room is the clacking rocker or whatever was making all that noise in your video. Cats don't generally cause misfires - misfires kill cats and plugs them up so they are restricted and engine has little power.

Start by checking compression. Then pull valve covers and inspect rocker movement - look for differences.

 

A compression test is a reasonable suggestion .

George

 

If the OP finds nothing with the typical static compression tests, then I would suggest checking all the mechanical stuff out (even testing for restricted converter) by doing the running compression tests in the following link. Best thing is it's all free and requires no parts cannon!

https://www.alldata.com/us/en/suppor...pression-tests

 

Thanks all for your contribution

So about o2 sensors voltage, my front sensors are ok (0.1-0.8v) but back sensor is not, its almost similar to front (jumping between0.1-0.8v) when it suppose to be steady at ~.4v, which might mean that the cat doesn't work properly, but that might be a symptom, not the root cause

Minor updates here, I have tried to pull out the front O2 sensor, check if that would take off some of the "back pressure from cat" that I thought was there, but there were no changes in either behaviour after throttle nor intake pressure per MAP sensor data (it still goes down when I throttle on IDLE instead of going up), I don't have a tool to test pressure directly though O2 hole, but I ll get one soon to be certain
Also, I've tried to follow the noise, and it's more like from the bottom of the motor instead of the cats/exhaust

I had some suspicions about intake/exhaust valves, cause 2 previous owners used LPGs, and its common that valves burn out or else cause of gas operating temperatures are higher

I ll start with a compression test, if I can find tool for a reasonable price, but I hope its not valves(it hell looks like it), cause am not sure if am qualified enough to do that job myself haha
Gonna keep you posted, thank you

 

Most of the local auto parts stores in the USA have loaner tools (with deposit) like a compression tester.

I noticed that you are from a different country. Just curious which one. Austria?

If your rear O2 sensor is cycling like the front - then your catalytic converter is definitely bad. But that doesn't mean the cat is your performance problem - the P0430 is only an effect of your performance problem. Misfires are what kills cats. Also know that cats are not always restricted when damaged, which appears to be your case. Just forget about the catalytic converter until you have the engine running correctly. Back to basics!! Don't get lost in the OBD2 jungle!