New CAT going in,, Lambda advice needed

[Jp003]

Originally Posted by 960kg

This also may give an understanding to what function each O2 sensor does depending on model!

Hi 960Kg thanks for the information that is very useful to me.

I can tell you at present my voltage readings are Lower than 0.75 and 1.25 at idle, have to take a look at that whilst I'm driving to see if it increases. From the information you have provided it says I'm running rich.

The other thing that confuses me from the information you posted says "the rear sensor has been moved forward nearer to the front sensor, just in front of the monolith in the catalytic converter.

What does that mean? Is that saying the sensor is better off in the port on the neck before the CAT starts rather than in the CAT box?!

JP

[kevvydude]

right, i,ve spoken to a m8 that knows all abt fuel trimming, if you have no vacuum leaks, no exhaust leaks, 99% its the pre sensor,as the post does not affect fueling, it the pre sensor that will give the ecu the wrong signal, if it is not working prop then you,ll get a middle of the road signal, the best way to test is , bear with me, the red line and the tick over,work out the middle exact, the you car should run perfect at that revs, if it runs worse over or under that,then it the pre sensor,as it is not getting the sinal for the fuel injectors, the ecu will pick a middle of the road setting.and wont ness put a light up, s it need a constant failure signal to do that, if it has 4 wire the chances it the heat wire, they are the wire/fault with pre sensors,, the post has nothing to do with fueling, on a standard volvo, hope i,ve explaned it prop so you understand, regards kev

[Chris_Rogers]

"Chris mentioned a figure of 0.8 or 0.08 cant remember"

The figure of 0.8 is a MAF adaptation figure that can only be read by using Volvo's VADIS or Vida/dice when connected to the car.

The ME7 system is clever at detecting a faulty MAF sensor and compensating for it, maybe too clever because it makes diagnosing a faulty MAF sensor difficult without the Volvo dealer diagnostic setup.

From memory the air mass passed at idle should be around 11kg/hr.

The front oxygen sensor, which does most of the work, is a wideband type, you won't see a voltage change on this sensor via OBDII, it does not work this way.

[KBB]

Originally Posted by Jp003

I have recently bought a cheap colour touch screen scanner which does real time data. I have been looking at the fuel trims and the sensor seems to be working okay but I'm running rich, especially under high boost up to 30%.
Also I have been getting a code P1171 which is a manufacturer specific code. Volvo has told me this is a long term fuel trim issue, upper limit. This has recently been coming up every 50-100 miles and was pointing towards running lean which I'm not cause I've seen the data I'm running rich.
JP

If your scan tool is showing a fuel trim value of +30% then your system is running lean and the + 30% is the amount of additional fuel correction factor to get the system back to Lambda hence why the DTC is P1171.

If your scan tool supports freeze frame data look at it and see what the RPM was at when the DTC was set. You can narrow the possible faults down further by looking at the Short Term Fuel Trim (STFT) and the Long Term Fuel Trim (LTFT) at idle, again at 1500rpm and again at 3000rpm hold at those rpms for 30 seconds before taking the readings. If you can post those test results then diagnostic progress can easily be made.

To confirm if the upstream wide band sensor is working get some LPG, most techs use a plumbers butane torch. Hook up the scan tool and look at the fuel STFT, introduce LPG in through the air intake and look at the fuel trim values.

If the values start to go negative you have proved that the wideband sensor has responded to a rich condition and has backed off fuel delivery to gain lambda so sensor is not the problem.

The are some very good simple test's that can be done to confirm or deny system function before you start throwing parts at it.

[Jp003]

Originally Posted by Chris_Rogers

"Chris mentioned a figure of 0.8 or 0.08 cant remember"

The figure of 0.8 is a MAF adaptation figure that can only be read by using Volvo's VADIS or Vida/dice when connected to the car.

The ME7 system is clever at detecting a faulty MAF sensor and compensating for it, maybe too clever because it makes diagnosing a faulty MAF sensor difficult without the Volvo dealer diagnostic setup.

From memory the air mass passed at idle should be around 11kg/hr.

The front oxygen sensor, which does most of the work, is a wideband type, you won't see a voltage change on this sensor via OBDII, it does not work this way.

Thanks Chris and yes I am getting a MASS of about 12Kg/hr at idle so its there or there abouts.

I don't see any data on my reader for the first sensor as you say and my second sensor is a 5 wire sensor.

Broadband sensor (= 5 wires):
For direct injection and diesel
vehicles. Generates an electrical
current between –2 mA and
+3 mA depending on the oxygen
content in the exhaust gas.
▶ Compares the residual oxygen
content of the exhaust gas
with the oxygen content of the
surrounding air.
▶ Detects the transition from a rich
to a lean mixture and vice versa

The Bosch number for my rear sensor is LS 7070 or 0 258 007 070

[Jp003]

Originally Posted by KBB

If your scan tool is showing a fuel trim value of +30% then your system is running lean and the + 30% is the amount of additional fuel correction factor to get the system back to Lambda hence why the DTC is P1171.

If your scan tool supports freeze frame data look at it and see what the RPM was at when the DTC was set. You can narrow the possible faults down further by looking at the Short Term Fuel Trim (STFT) and the Long Term Fuel Trim (LTFT) at idle, again at 1500rpm and again at 3000rpm hold at those rpms for 30 seconds before taking the readings. If you can post those test results then diagnostic progress can easily be made.

To confirm if the upstream wide band sensor is working get some LPG, most techs use a plumbers butane torch. Hook up the scan tool and look at the fuel STFT, introduce LPG in through the air intake and look at the fuel trim values.

The are some very good simple test's that can be done to confirm or deny system function before you start throwing parts at it.

If the values start to go negative you have proved that the wideband sensor has responded to a rich condition and has backed off fuel delivery to gain lambda so sensor is not the problem.

KBB you are the man. I deleted all the freeze frame data the other day, lucky for me the P1171 came again yesterday and I haven't read or cleared it as yet so I will take some pics and post the data.

So I am running lean after all!!! Just takes one person who knows what they are doing and it makes things so much easier, many thanks.

I will conduct readings at idle, 1500 after 30 secs and 3000 rpm after 30 secs and post the data.

Does it make any difference if my engine is cold or up to temp?

I have a plumbers Gas bottle but I'm not so sure about putting Gas into my Air intake its a scary thought. I will leave that one for now nut out of interest where is best to squirt it in? Is this done with the engine off or running?

Many thanks JP

[Jp003]

Originally Posted by Jp003

Thanks Chris and yes I am getting a MASS of about 12Kg/hr at idle so its there or there abouts.

I don't see any data on my reader for the first sensor as you say and my second sensor is a 5 wire sensor.

Broadband sensor (= 5 wires):
For direct injection and diesel
vehicles. Generates an electrical
current between –2 mA and
+3 mA depending on the oxygen
content in the exhaust gas.
▶ Compares the residual oxygen
content of the exhaust gas
with the oxygen content of the
surrounding air.
▶ Detects the transition from a rich
to a lean mixture and vice versa

The Bosch number for my rear sensor is LS 7070 or 0 258 007 070

I need to correct this post, Ive just checked my car and there is a 5 wire sensor going to the first sensor and a 4 wire going to the second sensor. Is this correct or have I installed the sensors in the wrong place?! That might make a bit of a difference to the running of the car!!!!!!!!

If I have mixed up the sensors I will never live this down on here will I lol

[Chris_Rogers]

The 5 wire is a wideband sensor and is the front one.

The 4 wire is the simpler type and the rear sensor.

KBB is quite correct +30% fueling is adding fuel to get Lambda = 1.

I does not mean the car is running lean, it means that 30% extra has been added so it doesn't.

AS KBB says testing at various RPM and logging STFT will help narrow the problem.

[KBB]

Scan tool will display open if the O2 sensor is not warm and closed when the sensor is active and in close loop control and responding to fuel trim.

Yes better to test when warm as during warm up additional fuel is used.

The LPG test should be done warm with the engine running and introduce it into the intake side either straight in at the air filter box or I usually put it in through the brake servo vacuum pipe after disconnecting it. Open the tap gradually and observe the fuel trim reaction. Remember this test is used to confirm O2 sensor function which at the moment I do not think this is your problem.

Freeze frame data is key here in particular the RPM value at the time the DTC was set. Can you look for a live data PID that looks like "engine load calc" usually expressed as a %. Would you be able to get access to a fuel pressure test gauge?

[Jp003]

Originally Posted by KBB

Scan tool will display open if the O2 sensor is not warm and closed when the sensor is active and in close loop control and responding to fuel trim.

Yes better to test when warm as during warm up additional fuel is used.

The LPG test should be done warm with the engine running and introduce it into the intake side either straight in at the air filter box or I usually put it in through the brake servo vacuum pipe after disconnecting it. Open the tap gradually and observe the fuel trim reaction. Remember this test is used to confirm O2 sensor function which at the moment I do not think this is your problem.

Freeze frame data is key here in particular the RPM value at the time the DTC was set. Can you look for a live data PID that looks like "engine load calc" usually expressed as a %. Would you be able to get access to a fuel pressure test gauge?

Okay I will go to the car now and pull the freeze frame data and take some notes/pics and come back in and post the info.

Then I will take the car for a drive and get up to temp and come back and perform the required tests and again post the info on here.

I really appreciate everyone help and advice