Lingga marta

Dear all,

Can somebody show me the location of O2 sensor plug in my car (300E/87)???

I planned to check/adjust duty cycle on my own, but the readout on DMM is constant at 2.8-2.9V (positive cable on pin#3 and negative cable on pin#2) even after turning the adjustment. So maybe there's problem with my O2 sensor.

I doing this since the car sometime stalling when about to stop (decelarating) and the idle also sometime not constant (seems like hunting) around 650-750 when I put the shift on P/N and will drop to 550 when I put the **** to D

Regards,
Lingga

ps2cho

Stalling when coming to a stop will be the OVP (Overvoltage Protection relay) it sits behind the battery and has a fuse on top. First check the fuse, if the fuse looks OK just replace the unit. It can cause a number of issues with stalling and idling.

O2 sensor plug is under passenger carpet seat in a black box so pop open the cover and the two wires will be there.

If you need to replace it, splice in an O2 sensor off a 1990 Mustang GT. It is $38 vs $120 for OE. Same sensor, just minus the plug.

Lingga marta

Thx Ps2cho,

I've check the OVP fuse and it still OK, is there any way to check the OVP whether it's in good or bad condition?...

Until now I already try to clean up the IACV (open it and clean it with carb cleaner) somehow it maybe works, the car only stalling one time since I done it. But the problem with my idle is still there (hunting idle) Could it be caused by bad OVP?...

Regards,
Lingga

ps2cho

No way to "test" it. It is an item that is so common it affects 100% of ALL 124's which have it. Whether the owner or the mechanic is aware of it is another story. The problem is the joints crack over time. Some people have posted success of resoldering, but after a few days weeks the problem came back.

The OVP when not working properly sends the computer into open-loop mode so you will never get a stable idle. It is not something you want to skip over when it comes to stalling and rough idles. You can search and find thread upon thread upon thread on it across all forums

Lingga marta

Ok then, i'll replace the OVP and see what happen..

Thx,
Lingga

ps2cho

As your mixture is not fluctuating, you are not going into closed loop mode...so that is your goal. OVP and O2 sensor first.

virtual_law

Hello, I know it's been a while. But I have a similar issue with mine. My voltage is stuck at 7.5v and upon warm up to 80C, drops to 5.6v and stays there. I went underneath to check for oxygen sensor and it's entirely missing.

I am guessing the previous owner did away with it (along with the 4matic suspension) in favour of less fiddling.

However, did you figure yours out?