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Hi guys,

So my hdi 90 has an air doser, I have already plugged the vacuum on the egr to disable this.

Do you guys disable the air doser or is it a possibility?

Looking at my bulkhead there are 2 EV, one which goes to the egr which is now bunged and the other looks like it goes to the air doser, would this be correct?

Thanks in advance,
Gilly

There is no point disabling it.

It has two purposes on the HDi 90: the throttle fresh air when the EGR is open in order to increase the amount of exhaust gas being recycled, and to slam shut when you turn the engine off which makes shutdown less wobbly and prevents run-on.

The second function you want to keep. For the first you're better off pulling and bunging the vacuum supply to the EGR.

With the EGR disabled the car knows that something is up because it sees more fresh air then it was expecting coming in through the MAF when it thinks the EGR should be open. You may see this as an "intermittent fault" in PP2K. I've seen this promoted to a permenant fault twice in 6 years on my 407 -- both times I just cleared it.

Hey rwb,

Thanks very much for your reply... Very helpful indeed!!
I have already bunged the hose for the egr so looks like I'll just leave the air doser then.

Is the crankcase breathing system pretty good on the hdi's?
I see there are 2 breather pipes... One to the turbo pipe and one back down to the sump...
No viable leaks around the areas which is good.
I only ask as I wonder if there is any point venting the turbo pipe breather to atmosphere or catch can?

Thanks again

Don't worry about a catch can, as the oily air from the crankcase can act as a way to lubricate the turbo inlet

I believe later Hdi had no air doser ( 2003/2004 ) so a solid pipe can be obtained and used in place of the doser.

If your doser is leaking, which does happen, then I would certainly bypass it as soon as you can - but if there are no signs of a leak then maybe bypass it in the future as a precaution...

Don't forget to bung the vacuum pipes too - or remove them completely if you are confident enough with the vacuum system.

GingerMagic wrote: ↑Sun May 31, 2020 6:09 pm Don't worry about a catch can, as the oily air from the crankcase can act as a way to lubricate the turbo inlet

I believe later Hdi had no air doser ( 2003/2004 ) so a solid pipe can be obtained and used in place of the doser.

If your doser is leaking, which does happen, then I would certainly bypass it as soon as you can - but if there are no signs of a leak then maybe bypass it in the future as a precaution...

Don't forget to bung the vacuum pipes too - or remove them completely if you are confident enough with the vacuum system.

Thanks very much for this ginger
I will have a good look round the air doser to make sure there are no leaks, it was more of a precaution.
I will have a look into the later model option for a replacement pipe, then simply bung the vacuum pipes like the egr.

As always, amazing advice and knowledge from 406oc!!
Thanks again