No worries, but I'm not sure I've been of any help yet.
I was hoping that the coolant temp sensor would stop the engine ECU from going into closed loop but obviously I was wrong.rvca wrote: 04 Apr 2022, 21:39 I removed the c3 coolant temperature sensor and plug it to the xsara loom. I didn't remove the xsara sensor and the c3 sensor was measuring a constant temperature of 23º.
With the ignition on and the engine off, the pre-catalyst o2 sensor has a voltage of 0.45v, just like the post-catalyst sensor.
With the engine on (idle during all tests), and although the coolant temperature sensor remains stable measuring the air temperature, the engine goes to closed loop after 1 or 2 minutes. I notice the idle more stable, a little high, possibly the ECU is compensating for the low temperature.
The pre cat o2 sensor oscillates between 0.09v and 0.84v (what i think is good) and the sensor 02 post catalyst oscillates between 0.44 and 0.69v (may be not so good).
While the engine is in open loop the stats look good. But the engine ran fine so we knew that.
Yes the post-cat sensor shows converter not working so good but you aren't getting a low efficiency code yet. So don't worry about that.
OK. I think this is our problem but I'm not sure why. Both the pre and post cat O2 sensors are passive. That is, they are not powered. They produce voltage proportional to the amount of oxygen flowing across them...and nothing else! 0V indicates a rich mixture, 1V indicates a lean mixture. So why would both the pre-cat and post-cat voltages drop to (virtually) 0V?! Under ALL circumstances the post cat sensor should remain at about 0.45V. In open loop yours oscillates at between 0.44 and 0.69. Not good but makes sense. But for it to drop to 0.13V makes no sense (all the oxygen has been sucked from the atmosphere? I don't think so). The Pre-cat O2 sensor can give strange readings because it's at the mercy of the engine ECU and the air/fuel ratio. Here the reading indicates the mixture is very rich. That is actually possible. It is possible that the engine is running rich! But why only in closed loop mode???rvca wrote: 04 Apr 2022, 21:39 after a couple of minutes the injection light comes on (open loop due to system failure) and the values ??obtained from the pre-catalyst o2 sensor reading are between 0.11v and 0.12v and the post-catalyst o2 sensor remains stable at 0, 13v.
Is this cause or effect?? Is this what is actualy happening or what the engine ECU is interpreting? Why is the light going out and the ECU going back into closed loop when the system is still faulty? Or does it "come good" and the engine ECU instantly go back into closed loop?rvca wrote: 04 Apr 2022, 21:39 When the light goes off again and the engine goes back into closed loop, the pre-cat o2 sensor returns to values ??between 0.09v and 0.84v and the post-cat o2 sensor remains at 0.8v.. after a few minutes 0.3v. .. Strange.. I can't even understand these values.
I understand that with the light on I realize that the mixture is poor.. but why??
This data looks Okrvca wrote: 04 Apr 2022, 21:39 Other data that may help to understand what is going on
With the ignition on and the engine off:
Load: 76%
Vacuum: 1.3
Tps: 13%
Intake manifold absolute pressure: 97.0 Kpa
Timing advance: 64th
With the engine at idle:
Load: 35%
Vacuum: 1.3
Tps: 13%
Intake manifold absolute pressure: 45.0 Ka
Timing advance: between 4.5º and 7.5º
The load and timing advance data for key on engine off are erroneous because the engine is not running yet. That's fine. Key on engine on looks good.
I don't think any of these are your problem.rvca wrote: 04 Apr 2022, 21:39 The sensors other gear that I swapped with the c3 earlier were:
Ignition coil, tps sensor, purge valve, map sensor and iddle regulator
Ok. The only thing that I can think of is a stuck injector. But I cant explain why it decides to stick right at the moment the engine goes into closed loop!? I would have thought the engine would have stayed in open loop if the engine temp remained low (IE the coolant temp sensor reads air temp)?
There is an injector error code.
You said "the engine feels like it's running on 3 cylinders". If an injector is stuck open that's probably true.
I can only recommend 2 things. 1) Remove and inspect all the spark plugs and look for one more carboned up than the others. 2) Replace all the injectors in the Xsara for the ones in the C3. Or if removing the spark plugs show one carboned up, replace that injector.
), but the engine has returned to "life". Full of strength and vitality.