'94 540 running rich with CEL code 1212

[wheelnxj]

Hi all,

I have a 94 540 with 160K miles. I had been getting the different O2 sensor codes and corresponding lambda control codes for some time. Then i changed both O2 sensors. Didn't help.

Then the car stopped running. I determined the fuel pump to be at fault. After replacing the fuel pump the car ran again, but terribly. Before changing the fuel pump i had also changed the fuel pressure regulator and the throttle body gasket where it mates to the intake.

I just replaced the rear PCV plate and the intake manifold gaskets. The car idles a hell of alot better, meaning it idles smoothly now, however it is still running really rich. At least i think so because of the gas smelling fumes in the exhaust. I'm still getting a 1212 code which is for an O2 sensor.

Do they need time to clean themselves off. Do i need to reset the codes for the computer to fix the mixture. After i changed the backplate the CEL was not present for a very short time, then it came back with same old same old 1212. I thought i could drive it off. Doesn't seem to have helped yet.

Once i tried to let all the codes run after a stomp test and wait till it got to the end to clear the codes, but there were so many it just killed the battery.

I can't even sell the car beacuse i cant get rid of the CEL. Besides if it runs nice then i want to drive it. I'm coming up on smog check again, and i would like to not have to go to a shady mechanic to get it to pass like i did last time.

Thanks everyone,
Eric

[632 Regal]

if and when in doubt reboot the computer!!!!

especially after changing a componant so the computer can start fresh.

[wheelnxj]

how so? does disconnecting the battery cable do the trick?

[632 Regal]

search for the showgun reset (i think) basically you disconnect the battery leads off the battery, connect them together somehow (vice grips?) turn the key to the on position (position 2) wait about 15 minutes, turn key off, connect cables, start car, let idle for a few minutes then go for a drive.

this procedure in some instances has revived brand new vehicles from cars that ran like ****.

Hope it helps and in your case im sure it will.

good luck!

[wheelnxj]

The shogun reset only cleared the CEL initially the same code comes back. I've been reading a lot about the cats. If the engine was running rich after the o2 sensors were replaced can they be fouled and or the cats clogged with carbon. I really don't want to do new ones of either seeing how the o2s are less than 5k miles new easily, and i don't want to buy expensive catalytic converters. can they be unclogged? will a fuel cleaner help? i should also note the car seems to hesitate in acceleration, and also it only has been idling smoothly after its been running for a few and not necessarily all the time.

I'm so sick of my once beautiful car running like garbage.

[wheelnxj]

are there any more suggestions out there? i'm stuck, i've tried all the small things i know of, all that's left are very expensive guesses.

[billb]

are there any more suggestions out there? i'm stuck, i've tried all the small things i know of, all that's left are very expensive guesses.

...in my case, it was throwing 1222, O2 sensor out of range. I replaced the O2 sensor, intake gaskets, fuel pressure regulator before trying a friend's working MAF on my car, which cured it immediately.

Used MAF sensors can be sourced for around $100 each.

[wheelnxj]

where can these said $100 used ones be procured? ebay? how many miles on a used one is low enough? i live in Anaheim CA, is there anyone close who has a new/still good MAF that would be willing to let me test there's in my car, since afterall it's so simple to swap them in and out?

an additional note about the idle/CEL1212 problem: the beast idles at about 500 when most people seem to agree that 750 is where it should be.

[billb]

where can these said $100 used ones be procured? ebay? how many miles on a used one is low enough? i live in Anaheim CA, is there anyone close who has a new/still good MAF that would be willing to let me test there's in my car, since afterall it's so simple to swap them in and out?

an additional note about the idle/CEL1212 problem: the beast idles at about 500 when most people seem to agree that 750 is where it should be.

I bought mine from Stockton Auto, online, at www.stocktonauto.com. It was $85 delivered to me. They currently show a '94 740i in stock. 800-235-8733. I worked with Randy there.