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Auto Tech Guy
Auto Tech Guy, Friendly Toyota Tech.
Category: Toyota
Satisfied Customers: 304
Experience:  Toyota Certified Technician, ASE Accredited, Engine rebuilder, Turbo specialist, Engine Diangnosis
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1998 toyota camry v6 front spark plugs (bank 2 ) ...

Customer Reply

Customer: replied 8 years ago.
1998 toyota camry v6 front spark plugs (bank 2 ) only become black with soot after only a quick test ride. replaced Bank2 sensor1 02 sensor.Replaced and cleaned plugs twice.Rear bank stays clean.Check engine light will reveal Code 171 lean,also missfire #4,also 1156 code 02 sensor.
Expert:  Auto Tech Guy replied 8 years ago.

Welcome to Just answer!

P0171: System too Lean (Fuel Trim)


Air intake (hose loose)

 Fuel line pressure

 Injector blockage

 Heated oxygen sensor (bank 1, 2 sensor 1) malfunction

 Mass air flow meter

 Engine coolant temp. sensor



Code P1156 is not a code for you Camry....did you mean P1155?

P1155 A/F Sensor Heater Circuit Malfunction


Open or in heater circuit of A/F sensor

(bank 1, 2 sensor 1)

A/F sensor (bank 1, 2 sensor 1) heater




Well the sensor getting sooty is because its running rich... It runs rich because it knows it was in a "Lean" condition so it dumps fuel to be "safe". Lean is dangerous for pistons and engine health= too hot, blows holes in things.


What kind of driveabilty concerns are you having with this vehicle?


I'd make two suggestions first.

1. Check all your vacuum hoses, remove them one by one, inspect for cracked damaged ones. Also *air intake hose*, the camry v6 likes to break them. You cant see it by looking right at it.... you may need to pull it off and twist it a bit to see if you can open up the crack.... a crack in the hose will cause a MASSIVE un-metered air leak= lean condition.

2. Test you MAF sensor.

Also clean it with CRC MAF cleaner, not the terminals... the sensor elements themselves.


Good luck, let me know if you need anything else.


-Auto Tech GUy

Auto Tech Guy and other Toyota Specialists are ready to help you
Customer: replied 8 years ago.
If there is a problem with a hose or mass airflow sensor,why not the rear plugs fouling?The motor begins to skip at about 55mph,if you floor it tjhe motor smmoths out.The fact that it is only the front plugs is what confuses me
Customer: replied 8 years ago.
I appreciate yo ur answer,however ,i am still confused why the p[roblem is only with the #2 bank only .a mass air flow problem should affect all cylinders?

nk only?The mass air flow would affect them all.
Expert:  Auto Tech Guy replied 8 years ago.

I'm basing my response on the codes, not the condition of the plugs...

Short trips will cause the plugs to look sooty... they need to be HOT to be burned clean.

If I had to put 2 and 2 together:

The plugs are sooty, the codes are for lean conditions and A/F sensor failure + you replaced the A/F sensor...= I'd start looking farther down the trouble shooting chart than what i described...

Yes you are right a bad MAF or torn hose would be ALL cylinders...

You did put in a NEW a/f sensor correct? The a/f sensor you replaced was for the cylinder bank in question...

Let me know... we;ll keep working on this...