Help - New O2 Sensor Install Problem - Broken or Wrong Part?

[twebber]

Any suggestions would be greatly appreciated. The check engine light is on in my 1990 300TE and the idle is a little rough and low at around 500 rpm - sometimes it stalls too.

I purschased my new O2 sensor on ebay described by seller evalero1 as an "O2 OXYGEN SENSOR BOSCH SG497 MERCEDES-BENZ 300E L6 3.0" - the seller said it would "work great" on my car. This new sensor has four wires - two white (power / ground wires) and one black sensor signal wire and a grey wire for sensor ground. I have only 3 wires to re-attach this new sensor in my car. Two white and one black which I assume are the power / ground wires and sensor signal wire respectively.

I have attached the black wire from the car to black "sensor" on the new sensor and the two whites together too. I have tried switching the white connections around (just in case it matters) with no luck. I have left the grey wire on the new sensor unconnected in all attempts.

Can anyone give me some suggestions about what my problem might be and/or things to try next to solve this problem?

My first suspicion is the new O2 sensor from evalero1 is either broken or does not work in my car. If it does work, my second hunch is that maybe the grey wire does need to be grounded out on something? Third hunch is that the problem is not the 02 sensor at all. Any help is much appreciated.

I am considering myself successful when 1) the engine light goes off and the after that 2) the car idles evenly at closer to 1000rpm. Thanks again.

 

[television]

Before you do anything you must make sure that you have 12 volt going to the engine management controls. The OVR is one prime suspect, check that you have 12v on pin 30 and on pins 87. If the voltage from this device is low, the idle will be rough and low

Malcolm

 

[carabind]

Also, the fact that you have four wires going to three connectors rings alarm bells. Clearly not a standard part and in your shoes, I'd return it in that its not fit for purpose and not as described? Only way you'll really,really know for certain now is to try another new one?

 

[twebber]

Also, the fact that you have four wires going to three connectors rings alarm bells. Clearly not a standard part and in your shoes, I'd return it in that its not fit for purpose and not as described? Only way you'll really,really know for certain now is to try another new one?

Indeed, the replacement part was inexpensive and I took a risk purchasing it based on only the sellers confidence it would work. However, the fourth wire is described as a "signal ground" and the installation notes that came with this O2 Sensor mentioned that connecting to 3 wire systems would result in the grey wire being unused. My first though was try anther new one too...

TELEVISION: "Before you do anything you must make sure that you have 12 volt going to the engine management controls. The OVR is one prime suspect, check that you have 12v on pin 30 and on pins 87. If the voltage from this device is low, the idle will be rough and low"

I am going to follow up on your advice though I am not familiar with an OVR is nor where it is located. I can research this though and get back to the forum if I am unlucky. Television, would a probelm with the voltage (as you describe) result in the check engine light going on? The reason I ask is all the problem started "after" this light went on.

 

[twebber]

Bit of time between my original post and getting around to doing anything on this - the cars been sitting (but started once per week)...Here's a brief summary of what is happening.
1) I have replaced the 4 wire 02 sensor with the proper bosch 3 wire.
2) the "check engine" light is still on and the car is running the same as before which is OK when the car starts but then very low idle (400-600) when warm.
3) I have just pulled the OVR and put it back in (not replaced but put back in the original) then checked the voltage as recommended by Malcolm. The voltage appears to be close to 12v so likely the OVR is OK (but the car clearly is not!)

Side notes / maybe red herrings.

1) when I put the OVR back in the "check engine" light went away for about a 2 mile drive then went back on. The car was not warm yet so no observations about how it ran with this light off (as brief as it was) when warm.
2) the battery indicator light comes on after starting the car and then goes away after a few miles of driving - it would seem it is not holding a charge well.

Any advice on next steps to diagnose (or solve!) this problem would be greatly appreciated. Thankyou.

 

[eric242340]

Your next challenge appears to be the battery.

 

[twebber]

I agree that the battery would appear to be a problem but the symptoms (rough idle when warm ect...) all started when the "check engine" light came on. I am wondering if the low battery is another symptom related to whatever has caused the "check engine" light to come on.

What other issues would cause the "check engine" light to come on that could also lead to problems with battery? THanks.

 

[television]

First lets go back to th OVP relay. These things go intermittent through bad soldering, and that is the biggest problem with them. Take it out of the case and flow solder all of the connections using a cored flux electronic solder.

Malcolm

 

[OmniCognateNeutronRangler]

....using a cored flux electronic solder.

Malcolm

is that the one that takes you back to the 1950's when you drive over 88 mph?

 

[television]

is that the one that takes you back to the 1950's when you drive over 88 mph?

It sure is When my stock runs out its over to lead free, otherwise I am breaking the law and polluting the planet.

Malcolm

 

[daveenty]

is that the one that takes you back to the 1950's when you drive over 88 mph?

In one of the few DeLoreans to ever reach 88mph

 

[twebber]

I re-checked pins 30, 30a and the two 87e pins on the attached photo. All had 12v. The only thing is the "check engine" light is off again. I am going to take the car for a drive and see if it comes back on and then test again while its on. Strange that removing the OVP and re-installing seems to temporarily turn the "check engine" light off.

Malcolm, I am not sure what you mean by "flow solder" all the connections. Do you mean I should connect all the pins on the bottom of the OVP to one an other (attached picture number 2) with cored flux electronic solder?

 

[kth286]

twebber

What check engine light are you refering to ?????????????????????

 

[television]

I re-checked pins 30, 30a and the two 87e pins on the attached photo. All had 12v. The only thing is the "check engine" light is off again. I am going to take the car for a drive and see if it comes back on and then test again while its on. Strange that removing the OVP and re-installing seems to temporarily turn the "check engine" light off.

Malcolm, I am not sure what you mean by "flow solder" all the connections. Do you mean I should connect all the pins on the bottom of the OVP to one an other (attached picture number 2) with cored flux electronic solder?

Oh no no no no no no no.
Unclip the plastic cover and there is a printed circuit board inside. It is the tracks and component on the board that need to be soldered, they were bad from the factory, though looking at you picture that one is not that old.

The symptoms of the way the car is running do point to this.

Malcolm

 

[twebber]

David, the picture below shows the "check engine" indicator light in the lower right of the dashboard.

Thank for the clarification Malcolm. I just got back from another test run to see if the check engine light would come back on and it did NOT. Hmm. When this check engine light is off the car runs well. Given the behaviour and what you have said Malcolm, I think it is the OVP.


[the above was edited. I mistakenly thought the battery was dead - in fact I left the leads loose for convienence in testing and the negative lead fell off!).

 

[twebber]

Another test drive and the check engine light did come on. Idle became eratic again. I tested voltage on 87e pins and they were both 12v. I did'nt re-test pin 30 (but will later if I dont break the OVP).

I pulled the OVP again and am trying to pry off the black plastic lid. There are two metal pins (see photo) that appear to be securing it - I dont know about forcing the top off otherwise I think I might damage both the receptacle for the fuse and maybe other things that those pins connect to? Dilemna is if I dont get the top off, how can I fix it!!!

 

[television]

Closed thread

Why is the thread cosed for tweber and the 02 sensor and OVP relay

Malcolm

 

[twebber]

Hi Malcolm, I am wondering the same thing? I hope I did'nt inadvertently offend a moderator or break a rule?

 

[kth286]

twebber

I only just realised when you responded to my late question about check engine light, that you are across the Atlantic. We did not have that emissions fault logging facility in Europe on that generation of cars.
So, that may be one of the reasons.

There is a facility on your car to get the codes read and that is what you must do, rather than all this guessing.

 

[twebber]

Hi David. I did take the car into the Mercedes dealership - they said the code indicated an 02 sensor problem and were happy to replace it for me for approx $500. I did it myself (approx $100 for the bosch replacement). It would seem it did'nt do the trick. I have thought of taking it back to the dealership to get a re-read on the code to see if it has changed at all.

An update to my testing...while trying to pry the platic cap off of the OVP to I must have broken it. I ordered a new one (also $100) so I'll report back when I get that one installed. Thanks for your help.