207 keeps fouling the plugs

[ozvtr]

I'm pretty sure it's a wideband three wire O2 although I will have to check. The engine is a Prince EP3 VTi.

Should have 5 wires. The post cat (downstream) sensor will have 4 wires.
I would suspect the O2 sensor. I cant see how you can get a lambda of 1 with over fueling like that.
With excessive fuel consumption you should expect the lambda to be low (0.8-0.9 or lower). If the O2 sensor lambda is 1 or above, then the sensor is faulty.
Can you graph the O2 sensor voltage? It should fluctuate a bit as you load and unload the engine. If it's a flat line then the sensor is dead.
However, at idle, the output should be flat BUT the voltage should be very close to 2.5V.
I would expect yours to be 'stuck' above 2.5V but we shall see.

[camel]

However, at idle, the output should be flat BUT the voltage should be very close to 2.5V.

The upstream O2 sensor should always be fluctuating in cycles of 1 ... 2 seconds. Even when running idle. But only if the sensor is hot enough, which may take quite a few minutes after a cold start.

If the upstream O2 sensor is showing a flat value even when hot, there is a problem.

The downstream O2 sensor values are usually flat, although some vehicles may also show a fluctuating downstream sensor.

[ozvtr]

However, at idle, the output should be flat BUT the voltage should be very close to 2.5V.

The upstream O2 sensor should always be fluctuating in cycles of 1 ... 2 seconds. Even when running idle. But only if the sensor is hot enough, which may take quite a few minutes after a cold start.

If the upstream O2 sensor is showing a flat value even when hot, there is a problem.

The downstream O2 sensor values are usually flat, although some vehicles may also show a fluctuating downstream sensor.

This engine runs a wide band sensor not a narrow band sensor. The output is linear and does not "switch" like the narrow band output. The voltage (and lambda) may fluctuate as the engine accelerates and decelerates. If the engine is in tune, the output shouldn't change by much. If it was to fluctuate significantly or remain too high or to low it indicates that the engine ECU is having trouble compensating or there is a problem with the sensor.

[camel]

This engine runs a wide band sensor not a narrow band sensor. The output is linear and does not "switch" like the narrow band output. The voltage (and lambda) may fluctuate as the engine accelerates and decelerates. If the engine is in tune, the output shouldn't change by much. If it was to fluctuate significantly or remain too high or to low it indicates that the engine ECU is having trouble compensating or there is a problem with the sensor.

Ah, ok, I wasn't aware of that. Thanks for the correction, good to learn

[Frog1]

Can you point me to how Diagbox can show the fuel trims please.

Select "scan tool" when the option comes up.

Still can't find anything marked fuel trims to monitor live. There was no option for scan tool anywhere. Diagbox v7
I can see some fields marked richness control but they don't separate to long and short term.
There is a section in Diagbox marked 'Measurements' but this just says connect the measuring card, or something like that.
See below pictures for the fields I can see.

[Frog1]

We have been looking at this issue again today and going over some of the suggestions.
Firstly, we took the intake airbox apart to check that and see if it was possible to look for oil in the intake or for a dirty MAF.
The airbox was all fine but we couldn't get to the MAF without removing the intake, which looked like a big job and we should probably replace the intake gaskets if we remove that. No sign of any oil up to the MAF.

Then, after putting everything back together we tried squirting easy start around the intake with the car running and looking at the mixture correction data for a change, I presume this is like a fuel trim. You couldn't hear any engine note change from the easy start but there was a very slight increase on the graph shown below in the second and eleventh block, it dipped to around -7ish and then returned. No vacuum leaks can be heard. If there is a leak, it must be small.

Next, we started the car again and captured some data of it running. At this point it was running fine. Probably still over fuelling but from inside the car, it ran seemingly ok. Coolant temp comes all the way up to 103 and the fans kicked in above 105 C - All normal I think.

Once up to temp it smelled rich from the exhaust and you could see a bit of white smoke occasionally. (There is no coolant loss). I think it is running rich all the time. Here is some data from the warm up and for the next 15 minutes or so, mostly at idle, or maybe 2k rpm occasionally.

[Frog1]

The next thing I discovered is that there are two options in Diagbox for a 207. We had been using 207 CAN but I tried 207+. It all looked the same but it did find the codes we removed a few weeks ago that didn't return in the 207 CAN. Not sure if it has logged them again or they need removing from within both sections.

The car had now been running on and off for about an hour. Smelt rich and you could hear the odd pop from the exhaust and see a bit of smoke.
Next the car decided to start a little stutter and then pop the MIL on for a cylinder 4 misfire.

We took out the plugs and sure enough number 4 looks bad this time.

Here is the car having a stutter before the MIL (Engine light) and misfire code.

We cleaned the plugs up and replaced, the car ran fine again but rich still.
We then unplugged the upstream O2 sensor and ran it again. Obviously the car stayed 'Open Loop' but it was still rich from the exhaust and the same as before.

Here is some data captured during this last half hour. Can anyone see anything amiss?

[wurlycorner]

Good work plugging through that, I think.
Mixture Correction is the fuel trim, I believe.
Do you have any data for what the Mass Airflow is reading?

[mickthemaverick]

From a first look at those diags I am inclined to think the downstream sensor may be the issue. If it is reporting weak it will result in the ecu increasing the mix and hence running rich if it wasn't actually weak in the first place? Or am I talking gobbledegook?

[ozvtr]

The “upstream richness” is Lambda. 1= nominal.

The “mixture correction factor” IS the instantaneous fuel trims. For one reason or another, the PSA software doesn’t track long term fuel trims? Being at about 0% shows that the engine ECU “thinks” the mixture is correct. Anything +/- 5% is good.

“Proportional upstream oxygen sensor voltage” is just that. And at 1.5V that’s indicating a rich condition. Which is what you seem to have. But the engine ECU is not correction for it!? In fact the fuel trims say the engine is using the correct amount of fuel. That makes no sense.

The fuel trims should go negative for a rich condition (low upstream oxy sensor voltage) and positive for a lean condition. So the ECU should add fuel for a lean condition and reduce fuel for a rich condition. It’s not doing that. It’s staying around the 0%. What do the traces look like with the car accelerating and decelerating?

In the very last picture, the wide band sensor jumps up to nominal air/fuel ratio about ¾ along the trace. You can also see the O2 sensor monitoring the cat go down to 0V. This shows the system lean out. The upstream and down stream O2 sensors concur. Showing it’s not an O2 sensor fault.
It looks like, that just for a second, the system ran properly.

What this data tells me is that the engine ECU “knows” the mixture is rich, but that condition (rich) is correct for the engine at that moment. I can only assume the engine ECU “thinks” the engine is under load or cold? The coolant temp data looks Ok, and the engine ECU goes into closed loop. So it doesn’t seem to think that the engine is cold.

What does the MAF and/or MAP sensor data look like?

Can you run the MAP/MAF sensor and Proportional upstream oxygen sensor voltage at the same time. While accelerating and decelerating?

[Frog1]

Good work plugging through that, I think.
Mixture Correction is the fuel trim, I believe.
Do you have any data for what the Mass Airflow is reading?

Thanks.
See below for what I think is the MAF and MAP data.,

[Frog1]

From a first look at those diags I am inclined to think the downstream sensor may be the issue. If it is reporting weak it will result in the ecu increasing the mix and hence running rich if it wasn't actually weak in the first place? Or am I talking gobbledegook?

I don't understand why the downstream O2 reports a Weak or rich setting, or even a closed and open loop status specific for the downstream sensor.
Up to this point, I have been ignoring the downstream sensor because I thought it had no effect on running and it was only used for cat efficiency. Am I wrong on that?

[Frog1]

The “upstream richness” is Lambda. 1= nominal.

The “mixture correction factor” IS the instantaneous fuel trims. For one reason or another, the PSA software doesn’t track long term fuel trims? Being at about 0% shows that the engine ECU “thinks” the mixture is correct. Anything +/- 5% is good.

“Proportional upstream oxygen sensor voltage” is just that. And at 1.5V that’s indicating a rich condition. Which is what you seem to have. But the engine ECU is not correction for it!? In fact the fuel trims say the engine is using the correct amount of fuel. That makes no sense.

The fuel trims should go negative for a rich condition (low upstream oxy sensor voltage) and positive for a lean condition. So the ECU should add fuel for a lean condition and reduce fuel for a rich condition. It’s not doing that. It’s staying around the 0%. What do the traces look like with the car accelerating and decelerating?


In the very last picture, the wide band sensor jumps up to nominal air/fuel ratio about ¾ along the trace. You can also see the O2 sensor monitoring the cat go down to 0V. This shows the system lean out. The upstream and down stream O2 sensors concur. Showing it’s not an O2 sensor fault.
It looks like, that just for a second, the system ran properly.

What this data tells me is that the engine ECU “knows” the mixture is rich, but that condition (rich) is correct for the engine at that moment. I can only assume the engine ECU “thinks” the engine is under load or cold? The coolant temp data looks Ok, and the engine ECU goes into closed loop. So it doesn’t seem to think that the engine is cold.

What does the MAF and/or MAP sensor data look like?

Can you run the MAP/MAF sensor and Proportional upstream oxygen sensor voltage at the same time. While accelerating and decelerating?

Thanks for taking the time to look over things and reply.
I think that 1500mv may be correct for this engine's sensor. Diagbox seems to say as much in the text description when you highlight the field for 'Proportional Upstream O2 sensor voltage'. You can see it here.

Some of the graphs showing the Proportional Upstream O2 sensor voltage show a fairly flat line, while at other times there is more of a fluctuation, as shown in the other screen captures. The Lambda data does the same. Probably not enough to explain why it is so rich all the time and it fluctuates both ways, not just rich.

As for the momentary spike in the data you correctly pointed to, I think it may have been just after revving it, that the spike happened. You can see the sensor voltage drop from 4.5v to 0v on some of the other graphs. I I don't think these data spikes line up in time however and as you can only fit 2 on the screen at any one time, I can't see in the screen grabs. Not sure what is causing this, perhaps a VCI blip. The car doesn't react during one of these spikes that I could hear or feel.

[Frog1]

Today we looked at the air intake data. Here are some screen grabs hopefully showing the MAF and MAP data.

The values all look to be the same as the reference value. I can't see anything wrong.

Does anyone know what 'filling' is?

I did think there was an issue with the Cam Phaser solenoid (9% off the reference value) but the Cam phaser position matches the reference (60).

The car clearly runs rich but I can't see anything on the data to confirm this. What are we missing?

[Rp0thejester]

Firstly I would ditch the plugs and replace with 4 points. No need to gap. Secondly, and this is a long shot, check the exhaust gasket is still intact and not leaking. This could stop proper readings getting to sensors and forcing the car to over fuel. Not everything on a car is monitored electronically, this maybe a mechanical issue.