The throttle body is clean. If I disconnect the actuator the OBD picks it up, the MAF and MAP sensors are giving sensible values. I'm going for the air leaks, the throttle may be a red herring? But I cannot find a leak anywhere. Is there a possibility that the MAF sensor may be giving what appear to be sensible values but actually incorrect when the ECU compares actual airflow? BTW, how does it calculate the dfference between MAF values and actual?

Just now, AOwen said:

The throttle body is clean.

Fair enough. Don't think you'd mentioned that to date. 

 

PCV system fault? Not sure how these work on the CR engines.

 

1 minute ago, Wino said:

Fair enough. Don't think you'd mentioned that to date. 

 

PCV system fault? Not sure how these work on the CR engines.

Apologies, it's difficult to include everything! 🙂 PCV is clear, the valve diaphragm is good, she's breathing a little heavily but not too bad. 3 days ago it took about 10 miles for the ECU to register the "Air Leak" fault, now it takes about 200 yards, so whatever it is has clearly got worse. Do these engines have "favourite" leaky bits or is it just random?

When EGR is commanded and everything is functioning as it should then the EGR valve opens, the throttle valve closes partially increasing manifold depression to suck through the EGR gases together with the incoming filtered air, this will result in a lower airflow going through the MAF, if the ECU does not see this, usually becuase someone has blocked off the EGR pipe it will throw up a fault code & MIL light & probably go into limp mode, not certain of the latter.

 

Hence the reason that EGR emulator/simulators exist, when EGR is commanded they tell the ECU what it wants to believe from the MAF sensor rather than the true value that it is reporting.

1 minute ago, J.R. said:

When EGR is commanded and everything is functioning as it should then the EGR valve opens, the throttle valve closes partially increasing manifold depression to suck through the EGR gases together with the incoming filtered air, this will result in a lower airflow going through the MAF, if the ECU does not see this, usually becuase someone has blocked off the EGR pipe it will throw up a fault code & MIL light & probably go into limp mode, not certain of the latter.

 

Hence the reason that EGR emulator/simulators exist, when EGR is commanded they tell the ECU what it wants to believe from the MAF sensor rather than the true value that it is reporting.

I've had the car since it was 9 months old and it's never been modded for anything. The OBD2 seems to think the EGR is OK. No other faults are raised, just the air leak. I guess that the throttle actuation not changing suggests that the EGR is not being activated?

Where does the air intake temperature get picked up? Mine is showing ambient T at 10 deg but intake T at 23 deg, should they be similar?

2 hours ago, AOwen said:

I've had the car since it was 9 months old and it's never been modded for anything. The OBD2 seems to think the EGR is OK. No other faults are raised, just the air leak. I guess that the throttle actuation not changing suggests that the EGR is not being activated?

Thats a reasonable assumption, my posting was a reply to your question: "how does it calculate the dfference between MAF values and actual?"

 

If you were measuring block values at a standstill I would not expect to see EGR activation.

All, thanks for your time. Problem solved, well at least found, small split underneath in the short rubber pipe immediately after the turbo.  You were right all along about checking for leaks, it was the "throttle" position that was bugging me, but that's really just for the EGR process. Last time I did serious commercial car spannering we were really chuffed to have central door locking! Things have moved on.

Glad you've found your solution!

5 hours ago, Wino said:

...Just trying to help the OP understand his car. 🙂

 

Red.

 

Herring.

Well done sep. 

Well done on finding it.

 

I almost put a posted about that you might be thinking at a higher level than needed and it's always worth re-checking what you've already checked or double-checked or thought you already had.

 

Now c'mon admit it, the apprentice would has got the seat of his overall dusted with the toe of your boot for missing that back in your central door locking days, whilst you and your colleagues would have admitted between yourselves that you didn't see it either. 😁

 

I once went off looking for a spare portable tester because the one I had been given wouldn't power up, neither did the spare, tried it in another power socket and it was fine, though I'd asked if all the sockets were live and was told "yes" of course I'd found one on another circuit that was dead, "oh, no, not that one over there".  Not only test the test equipment, test the tester, that really tested me, was on piece work and lost my place to the easy and quick gravy-train work.

 

30 minutes ago, sepulchrave said:

 

Red.

 

Herring.

 

46 minutes ago, nta16 said:

Well done on finding it.

 

I almost put a posted about that you might be thinking at a higher level than needed and it's always worth re-checking what you've already checked or double-checked or thought you already had.

 

Now c'mon admit it, the apprentice would has got the seat of his overall dusted with the toe of your boot for missing that back in your central door locking days, whilst you and your colleagues would have admitted between yourselves that you didn't see it either. 😁

 

I once went off looking for a spare portable tester because the one I had been given wouldn't power up, neither did the spare, tried it in another power socket and it was fine, though I'd asked if all the sockets were live and was told "yes" of course I'd found one on another circuit that was dead, "oh, no, not that one over there".  Not only test the test equipment, test the tester, that really tested me, was on piece work and lost my place to the easy and quick gravy-train work.

 

🙂 In those days a Renault 4 only had about a dozen wires.

Vehicle technology has accelerated hugely in the last few decades.

20 years ago I was writing computer code to solve 3D Navier-Stokes equations; now I have to ask my kids how to use MS Teams!

1 hour ago, AOwen said:

🙂 In those days a Renault 4 only had about a dozen wires.

Wow you do go back a bit. 😄

 

 

1 hour ago, AOwen said:

Vehicle technology has accelerated hugely in the last few decades.

C'mon, it was a split in a pipe, cars are ancient technology basically.  You'd be sent to make the tea, only then there's the worry of the hot kettle and water. 😄   Don't worry I wouldn't have found it until my wife pointed it out to me, "is this it" - "no, that's to make it easier to fit".

 

What's MS Teams then . . .

 

All's well that ends well, tomorrow is . . . usually another and different problem, but it's only a car, nothing important.  🙂