I am at the point of giving up on my 06 TL, I am in desperate need of Help at this point and im hoping the forum can help me Deeply. i will be as Detailed as Possible!

Eactly 11 Months ago my Check engine light for P0174 (Lean Bank 2) Came on and ever since then the car has never drove the same.
- Shaky Idle (RPM no IDLE Fluctuation from 654-700)
- LACK OF POWER (unless i Floor it)
- Car Starts up with a jerk and has a Deiseling effect when turned off (It rumbles and then stops)

So this Check engine has a Tendency to Turn on, and Go off By Itself after 4-5 Start ups.

After i Noticed that i Did the Following:
- New Spark Plugs (NGK)
-Sea Foamed
- Fuel Injector Cleaner Additive (TECHTRON)
- New o2 Upstream Sensors for both banks(DENSO)

I realize now that i might have bought a Different Brand Sensor for one of them and it wasnt a Denso it was a BOSCH THIS MIGHT HAVE CAUSED A PROBLEM IM NOT SURE, LET ME KNOW PLEASE

The Problem went away for a Month and back to the same nonsense...
in that month i replaced
-Front,Rear and Side Mounts (OEM)
- Power Steering Orings (OEM)

I still feel Vibrations at idle (Pretty Mild and they would go away once accelerating Slightly)

So i went to a NEW TRUSTY Mechanic. HE CHARGED ME NOTHING TO DIAGNOSE MY CAR TWICE, NICE GUY

At first he said it might my the Valve clearances or Timing belt could be off because nothing else seemed to be bad.

I was planning on doing the belt job but i DIDNT think it was the timing i WENT WITH MY GUT FEELING and found my OB2 Plug and Torque App

Early morning i realized the Car Sometimes gives off a Smell when i come out. I cant tell what it is and thats when i realized maybe its a head gasket or the Cat. So i plugged in the OB2 and i saw a new Code. P0420 (Cat Effeciency Below Standard BANK 1 THIS CODE ISNT A RED SOLID CODE IT SHOWS IT YELLOW AS A WARNING

THE CONFUSING THING IS THE LEAN BANK is BANK 2 BUT THE CAR IS NOT EFFICIENT IN BANK 1

Once the Car Warms up the P0420 Warning Goes away. So is the Smell the Cat Burning

I took it back to the mechanic and he says the Car is showing signs of a Head gasket leak in the Mornings but then it goes away once the engine Heats up.

MY LAST OPTION IS Steel Seal and CataClean or just Sell the Car....
WHAT COULD THE PROBLEM BE? Clogged EGR? Clogged CAT? The O2? HEAD GASKET?

 

Change the Bosch 02 back to a Denso, just incase. Some peeps have had problems using the Bosch.

 

If the OEM o2 sensor doesn't work, your cat may be on the way out

 

Do you think that can cause the Rough Idle and Power Loss? Will Cata Clean be a good solution until i sell it

 

Update. I realized I have a Denso o2 in the front and NGK in the rear.

 

power loss yes. rough idle shouldn't be due to a bad cat, you might just have a lot of carbon deposits or your IACV is stuck or you have air in your cooling system.


I don't believe in those snake oils, it's just going to delay the inevitable or 'work' for a bit..

 

There is no IACV on this car

 

P0174 easy reading:
P0171 and P0174 - OBD-II Trouble Codes

P0420-Cat efficiency. Change the sensor and if the code returns as it probably will, cheap/easy fix is to use 2 spark plug non foulers then install the O2 sensor. Illegal, but info on the how to do the spark plug non-fouler trick on google.

 

I'd bet that both your cats are clogged and causing issues.

 

A bad cat most certainly can cause rough idle problems. Perhaps YOU should google search more.

OP, remove your EGR valve and ensure that the valve is not stuck in the open position with a piece of the catalytic converter substrate.

Reference this thread to see what to look for embedded in the EGR valve and how to diagnose the front cat via the oxygen sensor:

https://acurazine.com/forums/problem...ailure-938132/

The thread link above relates to high-flow pre cats (HFPC), but the substrate of a normal cat can fail and do the same.

 

When I had my 02 RSX, my car threw 0174 code so I changed my bank 2 O2 sensor with Denso. 3 days later, 0420 came on and all I did is just put a cheap defouler from Autozone and it "SOLVED" the problem. I passed the state inspection with that condition though.