O2 Sensor

I just replaced the O2 sensor on my 1989 300E. When I fired it up it ran great however when I floored the throttle some white smoke came out of the exhaust and the engine started to miss violently as though something was cutting out at high rpm's. Does changing the O2 sensor reset the mixture the engine senses? Before changing out the O2 sensor I noticed black smoke comming out the exhaust at high rpm's but no violent shaking. Mixture too lean know or what? Thanks for any comments!

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Originally posted by Josie's Dad:
I just replaced the O2 sensor on my 1989 300E. When I fired it up it ran great however when I floored the throttle some white smoke came out of the exhaust and the engine started to miss violently as though something was cutting out at high rpm's. Does changing the O2 sensor reset the mixture the engine senses? Before changing out the O2 sensor I noticed black smoke comming out the exhaust at high rpm's but no violent shaking. Mixture too lean know or what? Thanks for any comments!

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Originally posted by tad:

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The first thing you need to do is check the lamda settings. It is possible that if the lambda was set with a bad o2 sensor and now you have one that is reading correctly the engine could be running to rich or lean. If you do'nt now how to check the lamda I can walk you thru it, although you will need some tools such as a digital amp meter and an eha test harness. The harness can be purchased thru your m/b dealer. Also why was the o2 sensor replaced?



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tad

Thank-you for the response Tad! The O2 sensor was replaced because it was the original from 1989. Thought it wouldn't hurt and might help. Please walk me through the Lamda testing process. I will need to buy the eha harness and digital amp meter. Good to have these anyhow! Thanks again Tad!

[J.HIDALGO]

Tad, I am also interested in the procedure for general knowledge, as many other people in the forum, I am sure.
TIA


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J.H.
'86 300E

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Originally posted by J.HIDALGO:
Tad, I am also interested in the procedure for general knowledge, as many other people in the forum, I am sure.
TIA

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Once you have the amp meter and harness Part #102589046300ks you can remove the air filter housing to locate the eha which is located on the back side of the fuel distributor. It is a small black box with a two pole wire connector on it. Your harness will plug into the vehicles harness and the eha. There will still be a third connector this is were the amp meter leads go. Make sure the positive lead of your meter goes to the solid black wire on the test harness. Turn the ignition on engine off and you should have a reading of around 19 mili amps. If this reading is ok start the engine and let it warm up to operating temp. You should see the amp meter moving back and forth across 0 amps. 0 amps is your mid point so you should have even movement on the negative and positive side of 0. If you do not have this reading you will need to adjust the lamda. This is done buy moving the screw down inside of the lamda tower, which is located on the left side of the fuel distributor. I believe it takes a 3mm allen to adjust it. If there is a metal ball in place on the top of the tower you will need to get a new lambda tower and break the old one off. Install the new one and make your adjustments. The new tower will come with another steel ball its up to you if you want to reinstall it. Once you have the lamda set correctly at idle you need to bring the rpms up to 2500 and the lamda readings shouldnt change within 15% of your idle readings. If it does you have further problems. Also while your doing this make sure the eha isnt leaking fuel they prone to do this after some years and mileage. Hopefully this helps any more questions please e-mail me.

Thanks alot Tad! I've purchased the amp meter but don't know where to purchase the harness part you mentioned. Is this a MB part or can it be found at Radio Shack etc? I did indeed notice the eha leaking awhile ago and replaced it. Thanks again Tad for your time and patience! George

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Originally posted by Josie's Dad:
Thanks alot Tad! I've purchased the amp meter but don't know where to purchase the harness part you mentioned. Is this a MB part or can it be found at Radio Shack etc? I did indeed notice the eha leaking awhile ago and replaced it. Thanks again Tad for your time and patience! George

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You can get that part at any M/B dealer just give them the part #.