M606 - so what do all these valves do??
 

I decided to take apart the air intake system to decoke and hopefully improve idling etc.

I knew there was a butterfly flap between the air filter and the EGR valve but I also discovered two more , one underneath the cross over and another where the crossover meets the intake manifold. The one under the cross over was completely stuck and would not move until I cleaned it.

Can anyone explain to me what these three butterfly flaps are supposed to do and in what circumstances do they open :confused:

I also noticed that the large one just before the EGR seems to be slightly open by default - is this correct?

I took some pics for reference if this helps:
http://photos.wanadoo.co.uk/album/1414673

thanks in advance
Keith

They all control the flow of air into the engine to maximum power throughout the entire RPM range.

Although this OM606 is naturally aspirated (non-turbo) it has variable-length or 'tuned' intake runners. The valve is used to 'tune' the intake depending on lower or higher rpms to improve exhaust scavenging and combustion air intake, a poor man's supercharger... :D

Do a search on Resonance Flaps. This valve can cause power surging if it does not operate properly and tune the intake as it should.

Sorry, I don't know which states they should be in at any given time...


Best Regards,
Jim

to block or not
 

Jim
thanks , the resonance flaps search really filled me in on a lot.

One thing I am still confused about though having read those threads and others on the EGR is whether or not to block the vacuum line to the EGR in order to reduce gunk build up.

there seem to be mixed views ?

Keith

Keep reading through the threads. You cannot block it because the ECM will throw a CEL and the engine won't run the same. Keep readind, it's described what to do bypass this safely. It's really the CCV system that is responsible for the goop. When the oil vapors from the crankcase meet the xhaust soot, there is your mess.

Hmmmm......are you certain that the ECM on the 95 models monitor the EGR? I have a "malfunctioning" EGR and have not seen any codes pop up, and it runs fine. Correct me if I am wrong, but my understanding is the 96 and later had the ECM monitoring the EGR.....at my age, I get confused easily ;)

The 95 and earlier models don't have the ECM monitoring the EGR- there are no sensors at the EGR valve.

Keith- did you have fun cleaning the crud out- have you put it back together yet? if so any joy with your rough starting?

All
yep lots of fun cleaning thanks. Found large build up of dry soot from EGR through to and including inlet manifold. Not sure where the sump fumes enter the system but it looks to me like it comes from the EGR. The EGR itself has the same hard crusted soot on it.

anyhow I physically brushed it all out and vacuumed as much out as I could. I also freed up the resonance flap (as I now know its called) which sits under the crossover. This was non operational due to the crust of soot, so it now works.

I think it idled cold better the next day but I'm not totally sure as the weather is getting warmer which means i am having less cold idle issue anyway. My wife is using the car for next few days so I will definitely get feedback on whether its improved or not :rolleyes:

In short the jury is out on the cold idle improvement but I am glad I have freed up the non working resonance flap. I like the idea that things work the way they were designed to.

Based on posts on this thread am still not sure whether to disconnect EGR. I have done it temporarily and it does not throw any errors at least. Am not sure on balance whether there is benefit (performance or clean intakes) . any view.

Also is there a cleaning agent that would get all the soot off my intakes, i couldnt remove it all with the brush?

I'm still not sure on the EGR myself. When I first disconnected it it felt like I had more power around town, but that might have just been psychological... me wanting to think it was better so it was!

On the motorway I can't really say I've noticed any difference. I may plumb it back in this week and see if there's a noticeable change.

To clean the intake I've read that carb cleaner isn't really strong enough for that crud. I used what I had at home (WD40, toothbrush) to get the worst out.
I know some members have taken theirs to be professionally cleaned or used bio-diesel etc to clean them out.

Off the line it may appear that it has more power, but when the revs start to climb all the "power" dissappears. :rolleyes2

It did not improve cold idle
 

Ok the official verdict from my wife is that there is no improvement to cold idling after starting :eek:

So i am happy that i freed up the resonsance flap but it hasnt helped. any ideas on my cold idling conundrum? :confused:

Keith

As of 6 month ago, my resonance flaps, as well as my EGR valve, stopped working all together. Could be electrical wiring problem related, or vacuum related, although I suspect electrical. Could be the EGR relay. I am waiting for a nice warm day so that I can remove the cross-over pipe and diagnose the problem.

I can tell you for certain, that my car does not appear to start or run any differently, with the the resonance flaps, EGR and who knows what else, totally inoperative. It seems to start and run perfectly. That's one of the reasons, that I was not motivated to fix it earlier.

There is however one thing that I did notice. I do keep meticulous records of my fuel milage, and I did notice that around the same time that my system failed, my fuel milage took a drastic hit. I was getting an average of 33 MPG, and now I am averaging 27 MPG.

So based on my experience, I would say that your cold start/idle difficulties are not related to the resonance flaps. Could be Glow-plugs, Over Voltage Relay fuse, the notorious wiring harness problem, or something else totally.

Phil

starting to put money on wiring now
 

I'm begining to think wiring - since I checked everything else as far as i can tell. Still car has been a good'n so maybe it deserves new wiring from me. I was hoping i might escape the wiring issue living in a climate with no extremes but looks like i must take the pain like everyone else :sick:

thanks for takin time to respond.