I was asked to plug the Nanocom into a '99 diesel yesterday. The problem with it was the idle was hunting between 500 and 1200rpm and it had stalled at junctions a couple of times. The owner had checked a few things himself and found that the air filter element had collapsed so he had replaced that and it seemed to cure the problem for a couple of days (although he said it still didn't seem 100%) but now it had come back. He had also removed a tuning box but that had made no difference either. It has had the EGR blanked if that is at all relevant.

Read the fault codes first and there was one for low boost but as it had occurred at 61rpm, that would seem to be an error as there won't be any boost at 61rpm and a low fuel pressure code at 0rpm so that would also seem to be erroneous. Cleared the codes, checked the Turbo-Intercooler- Intake hoses and no sign of any splits or anything that would suggest a leak. Started the engine and there was definitely boost there when revved. So used the Nanocom to check the inputs to the ECU. Most of them meant absolutely nothing to me (knowing naff all about diesel engines) but one stood out. The intake air temperature was showing -38.88 degrees C. On a petrol that would mean the sensor was open circuit, so unplugged the MAF (as it appears that much like the Thor petrol, the temperature sensor is incorporated in the MAF sensor) and gave the plug a squirt of contact cleaner. Interestingly, with it unplugged, it made no difference whatsoever to the running. With it plugged back in, it was still showing -38.88 degrees so we assumed the sensor is dead.

On a petrol, the intake air temperature only has any affect if it exceeds 55 degrees C when it richens the mixture, so assuming the diesel is the same, ignored that for the time being. Wondered if the diesel has the equivalent to the reset adaptive values on the petrol so went into the Utilities and there were two options, Reset ECU to Robust and Reset ECU to Non-Robust. Had no idea what either of these mean, I chose the non-robust option and as soon as I hit the button, the idle dropped to normal speed, it stopped hunting and it ran as sweetly as any oil burner ever can. It seemed that we'd cured it. Switched it off and restarted it a few times and each time it would fire up normally and the idle was perfectly stable. I then recorded the inputs on the Nano in case anyone can see anything obvious but as it was running perfectly at that time I suspect not (but if anyone is interested, it's here https://drive.google.com/file/d/1_0mA98hkmP2nPpYaJqkcNJLPQ9VayrNp/view?usp=sharing).

Owner has ordered a replacement MAF sensor but I'm intrigued as looking at the Nanocom documentation when I got home, it appears that the Reset ECU commands should only do anything on a brand new ECU so shouldn't have had any affect yet as soon as I hit the button, the idle stopped hunting and the car then ran perfectly. Anyone got any clues?

No expert but modulation is vital on these, stalling, poor hot starting and erratic idle are often mod being out. The chains stretch and throw the timing out. Engine hot must read 50% or near as. Moving the fip towards the block brings it down from a higher than 50% reading.

Richard, now only I saw this thread.
Though I'm not an expert on diesels by any means, must say that I too had a similar issue.
Looking at the data , you would see that the 'fuel quantity current' value is everywhere. Higher the no lower the quantity injected and 0 means flooding/
It should be around 5 when idling , hot engine.
Mine cured after adjusting it. You got to use 'hammer mod' to adjust the FQC.

Also, the timing modulation is too high as Chrisp38 noted, probably not starting when hot (unless hot start fix is fitted).

A replacement MAF was fitted and it still showed an intake air temperature reading of -38.88 degrees C. Checked the wiring between the MAF and ECU and no problems, full continuity on all wires. Out of desperation the owner got a replacement used ECU and the intake air temperature reading became sensible. That was a month ago and he has had no problems since.

In case it helps someone in future . . . . (not me cos I will not buy a diseasel.)

Set new ECU to robust mode:
This function only works on brand new EDC ECUs which
are delivered from the factory in a non-configured mode (factory mode), before they
can be used on a vehicle they have to be configured to either require a mobilization
code before they will work (robust), or to work regardless of any other factor (nonrobust).
This function sets a brand new EDC ECU to robust mode. It should be noted that
this function is only able to be performed once due to a restriction within the design of
the EDC ECU itself. It is therefore important that the correct choice is made.

· Set new ECU to non-robust mode:
This function only works on brand new EDC ECUs
which are delivered from the factory in a non-configured mode (factory mode), before
they can be used on a vehicle they have to be configured to either require a
mobilization code before they will work (robust), or to work regardless of any other
factor (non-robust). This function sets a brand new EDC ECU to robust mode. It should
be noted that this function is only able to be performed once due to a restriction within
the design of the EDC ECU itself. It is therefore important that the correct choice is
made.

Pete12345 wrote:

In case it helps someone in future . . . . (not me cos I will not buy a diseasel.)

That's two of us then......

This one was really strange and I expected there to be an equivalent to the adaptive value reset in the menu items. But, I admit, I know naff all about diesels, I mean, for an engine to run it needs compression, fuel and a spark and as a diesel doesn't have a spark then theory says it should never run in the first place.