Fuel Pumps

[Classik]

So I purchased the Sealey leakage tester, now waiting for delivery. It's got excellent reviews, and price is very decent.

Meanwhile I've been given a suggestion which is worth investigating for this air leak issue, namely the secondary air system.



It makes althemore sense that the discrepancies between MAFs occur ONLY when the engine is hot, whereas when it's cold (=when the secondary air system is active), MAFs are perfectly aligned. How does that sound? Of course it doesn't preclude to do a thorough air leak test when the kit arrives..

[Shoppinit]

Yes, Could well be a cause.

Lots of places for air to leak in on an RS6.

Checked for perished vac hoses?

[Ajc]

Theres only 2 vac hoses on the sia system and they come up too a solenoid under the air box , as Shop said vac hoses do perish , especially when that close too a heat source. If you haven't already , I'd consider changing them out . On a side note , I actually had a vac fitting broken off one of my combi valves when I bought my car , along with o e not connected at all too the fuel pressure reg . So worth a route round under the air box

[Classik]

All Vac hoses have already been replaced like 6 months ago, along with the N249 and N112 valves.
, but thanks for the reminder.

[Shoppinit]

What about the ones to the SAI valves? And the N80?

[Classik]

Of course I'll check those hoses asap. Never heard of the N80 though.. A quick search says it's a fuel vapor purge valve. How to check it's related to my problems, do you know where it is located? Thanks again!

[Shoppinit]

Behind the wheel arch lining. Right side, iirc. It has a vac hose going to it.

[Classik]

Just checked those hoses (parts 23&24) on the schematics above^^ and they're brand new. Before spending more money on parts, how would you check and repair those valves (parts 10 & 11)? Would a flush with brake cleaner do the trick as a first attempt of repair ?
Besides they are easily accessed BUT the screws (part 17) are upside down, meaning I need to find a specilized tool to unmount them!... Where is the facepalm emoticon?

Still need to find the N80 as soon as time allows.

As usual any suggestion is very welcome, and many thanks for the valuable help!

[Shoppinit]

Do not use brake fluid. It might perish the rubber diaphragms in the system.

To test the valves, do a suck test. Disconnect the hoses 23 and 24 at the engine side and suck. If you can suck sir through the valve it’s dead.

You might want to search for SAI delete to find out what horrors are waiting for you to access those upside down screws. Face palm indeed.

How soon does the maf reading stabilise? You said when the engine is warm, but the SAI kicks off after about 1 minute when the engine is far from warm.

[Classik]

Do not use brake fluid. It might perish the rubber diaphragms in the system.

Well noted.

To test the valves, do a suck test. Disconnect the hoses 23 and 24 at the engine side and suck. If you can suck sir through the valve it’s dead.

You might want to search for SAI delete to find out what horrors are waiting for you to access those upside down screws. Face palm indeed.

Oops, will do for sure.

How soon does the maf reading stabilise? You said when the engine is warm, but the SAI kicks off after about 1 minute when the engine is far from warm.

I don't know about you guys, but my engine warms quite quickly. I can't say precisely, but I'd say the discrepancies appear after 3 minutes or so; 1 minute seems a bit short to me. Would that disqualify the SAI route? I guess the suck test will tell.

Best

[Shoppinit]

Doesn't disqualify the SAI. When the engine is warm, the fuelling and load changes so the problem might still be there, just less noticeable. You can tell when the SAI kicks off: the noisy pump that sounds like a jet engine stops.

[Classik]

Besides, the best link on the subject I've found so far is this one: http://www.rs6.com/showthread.php/23678 ... on)-system. However the thread refers more to fault codes than possible air leak related to the problem. I guess just bypassing the N112 won't solve a possible air leak so I have to find a way to block the air injection down the line behind the valves 10&11, supposing it's an easy job...

[Shoppinit]

If your SAI is working OK I would leave it alone. Worry about it when it fails. The blanking plates need to be installed if you are deleting it and, as you've already found out, it's not easy to access. It might be working fine.

If you block the N112, which is what he did in that thread, then the SAI valves won't open and the SAI pump will strain against the closed valves. I'm surprised he didn't get any codes, but who knows whether his ECU had been modified or some other conditions meant that the SAI never tried to check the flow. Or his valves weren't sealed and the pump could flow enough not to generate a code.

This is the problem with SAI delete, you need to do it all properly or you leave the door open to future problems that you can't detect easily because you have blinded the ECU to the sensors.

When is your Sealey kit turning up?

[Classik]

This is the problem with SAI delete, you need to do it all properly or you leave the door open to future problems that you can't detect easily because you have blinded the ECU to the sensors.

When is your Sealey kit turning up?

Yes, that's also what I realized upon reading the thread and other sources. The Sealey kit is supposed to arrive sometimes next week.

[Classik]

Seems like every time I do a search about rs6 c5 air leak, I find a new suspect. Today's catch is the suction jet pump, or Y pump, located underneath the manifold (part 1):

But I guess this wouldn't explain the different MAFs readings between banks...

Good reading here : http://www.rs6.com/showthread.php/23948-Rough-idle