First, thank you to the members who reply without your help I dont know if I could keep my car running. I bought a 1997 E320 two days ago. It runs like a top, lots of power, however, check engine electronics light on. I scaned it 2 codes both each say to replace 02 sensor, I guess my car has 2 02 sensors...I then cleared the codes. No codes show for 80 miles, havent scanned yet, but figure 02 codes again.

Also hard to start sometimes. As in takes a few extra revolutions. Figured this was a CPS sensor (from all the info on this site) However having the 02 codes come back on could this be from colant contaminating sensors? I am lost because the car has power, does not smoke, havent changed oil yet, however stick looks perfect... But combine it with hard starting I am starting to get scared...
Any help would be apprecaited..
Thanks

 

per your other post what were the codes?
ohlord

 

What are the actual codes?
What is the mileage?
You have only had it two days so what is the service history?
Do a visual check on the air filter and plugs. Been changed recently? If not I would start there if high mileage.
COULD be contamination of the sensors. Does the car use coolant?
Has the engine had a gasket leak? Silicon sealants are the favorite contaminant.
You did 80 miles before the CEL returned. One journey or many? Did it come on whilst driving or at a restart?

Stuart

 

going to get codes written down this time, it went 80 miles after reset without CEL and check engine electronics light coming on. it has 104k on it. I dont see signs of head gasket repair. I will look at coolant today. Thanks alot will post codes today, as I travel to autozone...My question becomes if I reset the codes or clear them then 80 miles later while driving they come back on would I in the end by wasting my money on 02 sensors?

 

po133 and po140

 

Certain MB engines with aluminum heads are notorious for leaking head gaskets. But usually, they leak into the coolant system. If you keep changing the coolant, you can run them that way forever, although that's not a desirable state.

You can see evidence of oil in your coolant on a visual examination, or for the final say, use a block tester, Part # 700-1006 from NAPA. That is the definitive test for a leaking head gasket. I did a leakdown test and a compression test on my '92 wagon and all was well within spec limits. That's not enough, as the engine as to get heated and normal engine pressures reached (as in running).

I was getting ready to do the new head gasket service, but somebody broke into my garage and stole $5K worth of mechanic tools. So temporarily, I'm screwed.

Running with oil in your coolant will attack the rubber composition of your coolant hoses-hence the frequent coolant/flush procedure. The dealer will be incredibly expensive for this repair and a indie will be less-still very costly, however. Some MB owners have dumped their cars just because of this problem.

Kevin

 

P0133 = Slow response sensor 1 (Up stream)
P0140 = No activity sensor 2 (Downstream)

Confirm it looks like the O2 sensors but why did these give up? OK 104k miles. Mines are still running 140k.

Bad fuel of course can be an issue as can Silicon contamination from excess gasket sealet at a rebuild. Not sure if coolant is a particular contaminant, wouldn't be surprised BUT the issue here is whether you are using any. Coolant level at the correct mark should be riock steady if checked under the same conditions everyday.

Maybe its time to invest in 2 new sensors with the correct wiring connector. Make sure you get OE ones. This will save lots of problem down the road!

Others on this site know where to buy stuff in the States at the best price.

Stuart

 

thanks guys, having my friend mechanic come over, he has the scanner with the ability to read each sensors output... I will check the coolant level and drive the car. Probably will get a sensor or two if needed will keep you posted.

Any thoughts on a bosch sensor where I have to cut the wires?

 

o2's at 100k miles is normal replacement mileage
http://www.autohausaz.com/search/pro...xygen%20Sensor
about $115 ea delivery free.
easy diy install.
97 m104 had the upgraded head gasket so you should have no worries of that.
My initial opinion is someone recently sold you this car and just before doing so erased a known check engine light and Now you have inherited their problem. Always inspect,and that means taking a scanner with you and plugging it in.Or having a pro inspect it.If you purchased it from a dealer you may have some recourse.
ohlord
If you are handy with wire splicing you can wire in universal o2 sensors for your application for anout 60 bucks each.
rest easy on the head issue ,you would have far more problems than o2 codes if it was a head gasket failure.
Time to change the plugs oem copper bosch F8DC4 for the m104,,,no multi tip plugs or other crap.New connectors also.
Bosch universal O2 for the m104
15738 google bosch for retailers