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Exhaust gas contains very little or no oxygen and the engine wont run on pure exhaust gas. The butterfly will be closed only as much as necessary to increase exhaust gas to the desired level. However the ecm may determine that inlet pressure is too low for given butterfly and EGR valve positions and still record an EGR airflow fault.
Only in a petrol Graeme. Diesel exhaust has a lot of oxygen, even at full load up to 1/3 of the original oxygen is still present in the exhaust. Most EGR butterflys don't seal anywhere near closed.Quote:
Originally Posted by Graeme
I suspect the code description is abbreviated and the actual description would be something like "excessive airflow detected when EGR is activated". The excessive air-flow being measured in the MAF as the ECU expects to read a lower value.
Been doing some reading on the D3 uk site, and its amazing how different each car has acted with the same fault code registered. 3 08 models with EGR blanked have had totally different symtoms to the P0402 code.
Must be the joys of modern engine management systems.
Does anyone know if its posible to clean the EGR valve's , am thinking of maybe putting them back in, but may try and clean some of the gunk out whilst they are out.
Cheers Ean
Well what hapened ??? .
Nothing yet, been to busy, so still driving the car with the EGR's blanked and see how long it takes for the fault to register again. Its running fine so will address it when work slows down a bit and decide if I live with clearing the codes when they pop up or put it back together.Quote:
Originally Posted by Fatso
Cheers Ean
Cheers .
you must have SPESHUL petrols Dougals , Stoichy/AFR for most petrols is 14.7,and 14.6 for Diesel .Please explain where this extra oxygen is created under which conditions ? Graeme is right ,Dougal is wrong !
Diesels at full load are running 18-22:1 A/F ratio. This is where the 1/3 excess air (and excess o2 comes from).Quote:
Originally Posted by 400HPONGAS
Diesels never run at or near stoich.
At idle and low load diesels can be up to 80-100:1 A/F ratio.
As I said, there is always spare oxygen present in diesel exhaust. It is not "created", it is there from the start.
Gday All,
Well after a month of no faults and thinking all had finally settled down, I had a week of the same EGR fault almost daily.
The final straw came today when towing the trailer and the EGR fault came up 3 times in 20kms.
So I spent a couple of hours late this arvo fitting the EGR system back on the car.
I will try and play around with a few idea's over the next month or so, and it really pains me to put the EGR system back, especially after seeing the crud in the inlet side of the engine, but when the fault appears the car goes into limp mode, suspension drops and the dash lights up, and today was just to much to quick.
Still happy I tried and hopefully someone will work out how to do it successfully.
Cheers Ean
Bummer - but the guy on the RRS forum in the UK is still OK - he must have been a one off.