oigle
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- Redcliffe, Queensland, Australia
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- 2003 ML270 sold but not forgotten. 2022 Kia EV6 RWD LR
Hi Oigle,
Sorry to resurrect this post I imagine you're sick of talking about it, but would really appreciate it if you could answer a couple of questions.
I have a w169 160 cdi (A Class diesel) and before reading this post recently had the egr cooler, valve and inlet manifold off to remove a huge amount of black crud after 95k miles. Terrible sh1t, isn't it...
I too decided to delete the cooler, blank the exhaust and feed the egr valve with fresh air from the filter box, but before the MAF, you know where this is going. ...... yep, been there...
Yes, I eventually get a CEL which is diagnosed as "low boost pressure".
I can't use dieselman's circuit as the MAF is of the frequency modulated type.
Question: did you try putting a low resistance one way valve in the line feeding fresh air to the egr to prevent back feeding boost pressure to the air box? No. My experimentation showed that if you remove the exhaust pressure from the outside of the egr valve, the air flow goes out instead of in. There is no occasion where it goes the other way as diesels don't create vacuum like a petrol engine. Supplying fresh air to the valve is pointless.
Also, does the ECU look for a drop in MAF flow when egr operates at just idle or all rpm, at all revs. When the ecu signals the egr to operate, it also allows for loss of flow through maf. Of course, maf stops working from low boost onwards. as I don't get any DTCS for MAF volume to high at all, just low boost pressure, this is why I thought of the one way valve.
Really don't want to put the all the original egr cooling and pipework back, one because to do so means dropping the engine again, and two the crud build up.
The only other option would be to use a device from an American company called fuelsave. They do two MAF intercepts, one for variable voltage and one for variable frequency. I'm not sure the device would like to be fed by the modulated egr feed though.
Your input would be greatly appreciated. Haven't seen that one. I think with the frequency modulated type, the only real option (I have just done it on my Fiat Ducato motorhome) is to get it mapped out. Costs a few pounds (mine cost $350AU) but in the long term, I think that will be saved and more. EGR valve alone is quite expensive and labour to remove manifolds is horrendous.
Good luck
Ian
Colin