Engine subtle vibration / shaking tail tail sign of near clog catalytic converter

Engine subtle vibration until the dashboard area but there are no error fault codes when diagnose using the OBD2 scanner device. What could be the problem? This is happening to Alza car and the vibration still ongoing for quite sometimes. 

Apart from the vibration when the engine starting at cold start (early morning) strong smell like rotten egg emanating from the exhaust and of course the car unable to accelerate at full speed on the road despite pressing the gas pedal at full throttle. This is because the clogged catalytic converter suffocating the engine from breathing normally.

OBD2 fuel trim data also showing very rich exceeding the benchmark below -10% | +10% and it may spike up to -40% which is extremely rich or +20% for extremely lean. This is a sign the unburn gas during cold start unable to fully escape through the exhaust manifold catalytic converter and generating kick back which affect the oxygen sensor reading. So basically, exhaust fume generated from the combustions plus the kick back of unburn fumes caused the oxygen sensor to read extremely rich. However, pressing the gas pedal during cold start will see the fuel trim reading back to normal within -10% to +10% benchmark as the unburn fume being force through the clogged intake manifold.

Potential problems creeping from a bad front wheel bearings

After an experience replacing front wheel bearings lately - there is a feeling it's one of the most important components of the wheel that need to inspect occasionally and require replacement as soon as possible if it has gone bad. The wheel bearing is a very strong component that also helps to assist the suspensions to keep the car stable while driving on the roads. 

As the wheel bearings worn out it weakens the grip on the driveshaft and causing the wheel to wobble. If left too long for example years without replacing just because it's a minor wobbly the problem could creep to the cv axle differential bearings inside the gearbox which hold the inner end of the driveshaft. This is because the wheel bearing could no longer hold the driveshaft firmly on one side and automatically yank the other end back and forth which is being hold by the differential bearings.

And of course, replacement of the differential bearings will cost more to replace, and it require special tools, effort and time to get it done.

Elusive engine vibration can be felt on the dashboard area (Faulty O2 sensor)

The following diagnosis have been conducted 

1. Engine mount check including transmission mount

2. Spark plugs checked

3. Fuel injector checked

4. Transmission and engine fault code checked

Have exhausted inspections on all the major parts as above but there are still obvious vibrations can be seen on the engine and subtly around the dashboard area. However, have driven the car for couple of months nothing seems to be wrong until unprecedented check engine light symbol turned on. Upon workshop inspections by the OBD2 scanner the DTC fault code indicates faulty oxygen sensor. After replacement of the o2 sensor there seems to be some improvement in the combustion's performance crispier. In addition, the vibrations also seem to go away - could it be the faulty oxygen sensor providing wrong data to the ECU and in returns the ECU command inconsistent fuel injections that leads to the engine vibrations in the first place? It seems there is something to ponder on this.

A proof that liquid cell battery outlasts the maintenance free battery by far

After a couple of experience using the maintenance free battery at last have replace it back using the lead acid battery. It's a local brand or perhaps brandless battery called Enerlite and it cost 70% cheaper than all the maintenance free battery was installed on 27/12/2019 which is already lasted 2 years 10 months and still going. Most of the maintenance free battery lasted around 1.5 years and maximum nearly 2 years - which means the lead acid battery outlasts not only by the price but also durability.

Alza long term fuel trim running extremely rich at -32% ~ -34%

At cold start before the Engine Coolant Temperature reaches the optimum level around 83 ~ 85 degrees Celsius the fuel trim running extremely rich at negative 32% ~ 34%. This is crazy amount beyond the recommended range of -/+10%. When it reaches the optimum temperature, it usually oscillates around -20% ~ 14% which is still considerably rich.

At times it will down to -7% to -4% and then rises again to -12% ~ -14% after the car getting warmed up for longer time. The problem seems to be very elusive and not sure what could have caused such weird behavior of the long-term fuel trim. 

There is one of the most obvious signs to this problem when stepping on the gas pedal briefly the long term will go down between 0.0 to -7% which is very good and that indicates the car is lacking air for combustions. 

So, the presumptions analysis goes like this - At cold start the car run extremely rich around -32% to -34% and it goes down to -7% to -4% at optimum temperature @ 83 ~85 degree Celsius. As the car being driven and warmed up longer the fuel becoming thinner and capable to deliver more / faster but lack of air and the long-term fuel trim starting to go up around -12% to -14% again and sometimes -25% when running at idle or cruising without stepping on the gas pedal. However, when stepping on the gas pedal briefly the long-term fuel trim goes down between 0 to -7%. This concludes to a presumption that the car is lack of air flow when idle or cruising without stepping on the gas. But the real problem is what could have caused the lack of air?

These are few things tweaks that has been performed but no changes so far

Checking Parameters	Fuel Trim Improvement
Adding magnetic fuel saver	It seems to work for a couple of days but after that the fuel trim running rich again -32% maximum which is worst. This concludes that magnet have little effect to the fuel combustions
Torque Spark Plugs @ 17Nm	Nothing changes
Changed / clean fuel injectors	Not yet
Clean catalytic converter	Not yet
Clean Throttle body (ISC and TPS sensor)	Not yet
Replace air filter	Not yet
Replace pcv valve	Not yet
Replaced Oxygen Sensor ( O2 sensor )	No Improvement
Replace Map Sensor	Not yet
Replaced fuel pump	No improvement