P0420 CEL ON!

[bazar01]

Well, it happened yesterday.
CEL came ON but there was no change in performance though.
Hooked up the scanner and got 1 code P0420.
Immediately went to auto parts store and got new Autolite spark plugs and jumped on replacing all four plugs.
Spark plug holes were dry and no trace of oil.
Checked for vacuum leaks and all is well.
Reset the CEL.
So far P0420 has not come back after 100 miles.
Crossing fingers for code not to come back.

[bazar01]

CEL came back ON. Drove the car to lunch and I only put in 50 miles after the reset.
Next thing to do is get some CRC mass airflow sensor cleaner and clean the @#$t ouf of the MAF and hope P0420 does not come back.

If it does comes back, I have to look for my spare MAF that came with the engine I bought and replace that. It is somewhere still attached to the intake manifold. Hopefully I don't have to.

[bazar01]

I found my spare MAF, cleaned it with CRC MAF cleaner and installed it.
I need to get this car ready for emission testing before August 23 so the CEL needs to go away.

If I can get drive a full tank of gas without triggering the CEL I should be good for the emission test.

[hotmilk400]

You dont need to do a full tank of gas, you only need to do a drive cycle. google it, you will save yourself a tank of gas.

It's probably the reason your cars CEL did not come back on right away. A drive cycle is about 50 miles in an ideal situation.

Anyway, Good luck. If your other air mass sensor is no good, let me know. I can let you barrow mine to pass the inspection or sell it cheap or something.

Not sure if this will help: http://www.318ti.org/forum/showthread.php?t=35885

[bazar01]

Originally Posted by hotmilk400

You dont need to do a full tank of gas, you only need to do a drive cycle. google it, you will save yourself a tank of gas.

It's probably the reason your cars CEL did not come back on right away. A drive cycle is about 50 miles in an ideal situation.

Anyway, Good luck. If your other air mass sensor is no good, let me know. I can let you barrow mine to pass the inspection or sell it cheap or something.

Not sure if this will help: http://www.318ti.org/forum/showthread.php?t=35885

Great. Thanks.

Found this document online.

[bazar01]

Replaced the MAF with a used one that has 90k miles yesterday.
P0420 came back ON this morning on the way to work after 120 miles.

It looks like I need a new catalytic converter.
Time to drop and clean the cat and do the subframe bushings.

[mtlblue]

isnt' that the code for a faulty cat? maybe time for some new o2 sensors.. I had this problem show up on my 99 crv last year, after changing the cat for rust issues, got new sensors but not long after, it started coding, changed the sensors on garantee and after tests, we changed the cat again and that solved it. Before finally finding out that the cat was bad, I learned that you need to run the cat hot on it's first run to set it properly, so it "pops" into place,... or something, but it worked for me. fyi

[hotmilk400]

Awesome to hear.

As a side not, I just got the p0420 code yesterday. Go figure. My E46 has 248k miles and I am betting those sensors are original. With that millage and 4 sensors to replace, it will be a tough choice for me. Take care, update us if anything changes.

[bazar01]

No CEL as of today.
P0420 fixed itself by cleaning MAF and using 93 octane gas.
Thank goodness I don't have to replace the catalytic converter.

P0130 has not come back after replacing before and after cat O2 sensors.
It runs really good. Throttle response was better with new O2 sensors.
I am averaging now 31 mpg city. It used to be 29 mpg with old sensors.

[bazar01]

Still no CEL. Great!
P0420 has not come back ON. (Replaced MAF with used one with 90k miles and cleaned it with CRC cleaner)
P0130 has not re-appeared also. (Replaced 238k mile two O2 sensors) (direct replacements from Advance)

I am happy and it's ready for emissions testing and tag.

[hotmilk400]

It is probably the O2 sensors going bad. My girlfriends VW is doing the same thing. If you have the original sensors yet, I would bet it is them.

I cant remember if the 318ti can take the bosch universal sensors or not, but if they can, they are about 1/4 the price. the difference is they do not have the BMW connector, so you slice them into the old O2 sensor wire harness. Bosch website will confirm if your car can take them or now (typically the last sensor on the list) My GFs VW is fine now, no random PO420 code.

If you are passing the emissions inspection, getting good mpg, and dont care about the potential of damage to the Cat, i wouldnt worry about changing them. If the car had lower miles, i would suggest changing them. If you live in a state with picky emissions inspections (like where I live, or CA) I would change them. If you live in an area that doesn't do emissions once a year, i wouldn't worry either. Totally up to you and your budget. Not 100% sure it is the O2 sensors, which is why I am saying it is up to you. haha. $100 - $300 for sensors isnt something you may want to spend. if the car had lower miles, new O2 sensors will help MPG and would prob pay themselves off in 30k+ miles.

[bazar01]

I got 36.3 mpg during the 600 mile trip. Still good mpg?
New O2 sensors before and after cat converter installed 8-18-2014.

So far no CEL P0420.
I bought new intake boot and fuel injector vacuum distributor hose and plan on installing it this weekend. Hopefully, I can reinstall my refurbished LSD as well.

[bazar01]

P0420 came back during the cold morning commute. Outside temp was 49F.
The only change was using 89 grade gas the last fill up. I reset the code and will observe further. Then fill it back up with 93 and observe.

[bazar01]

Have filled up 4X using 93 grade and still no P0420. Did a 600 mile trip yesterday and still good. Weird.