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Intake manifold runner flap delete

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Hi everyone. I am curious about how to do this. Specifically, I have a 2012 Audi A3 with a GTX30 and integrated engineering intake manifold, which removes the factory runner flaps. I am using HP tuners for my tuning software. I've tried the search, and I can't find anything there or in the virtual courses about how to do this. The car starts and drives, but the revs jump up and down at idle from about 900 rpm to 1200 rpm to keep the car running, especially on cold starts. I can adjust the fuel mixture to run richer at idle, but is this the right answer? It seems like I should be able to make the throttle body function as the air idle control and let less air in. I would think that this is a better answer than increasing fueling. Please let me know if anyone has any thoughts on this or if you've approached it in the past and what your results were.

Nobody?

Can you adjust the fuel mixture to just run richer when cold? If adding fuel stops the surging, then that's an acceptable solution.

I assume your car is Drive-By-Wire, so are they adjustments to the idle DBW setup that could provide a bit more air, and a bit less timing to keep the idle from surging?

You might want to post some screenshot, or an HP Tune file so we could look at what's available as far as knobs to turn.

Thanks for the response. Yes, the car is DBW... but I would think that I would want the throttle body to provide less air at idle? I can absolutely run the car richer, I just wasn't sure if that was the "right" way to do it.

I'm actually in the process of moving, so it will probably be a week or more until I can get the car scanned and upload a file.

There are only three results of any change: Better, Worse, or the Same. Make a change and the whole goal is to decide if you keep the change, or reverse it and make another change.

Try it. See what happens. Maybe make some notes if you are worried about getting lost. Pay attention to trends - they will tell you if you're heading the the correct direction.

Before getting into it too much, I'd suggest double checking for vacuum leaks as I wouldn't expect a simple manifold swap to cause, in and of itself, a significant change - been wrong before, though.

Maybe review all the hoses and wiring is correct, and spray some engine start, or similar, around the gasket flanges to check for a change in engine note, which would indicate a leak.

That's a good suggestion. I know I don't have any boost leaks because I unplugged the MAF and the idle didn't change. I only have vacuum going from the vacuum pump (which is brand new) to a hardline that connects to the evap purge valve and another one direct from the vacuum pump to the brake booster. I'll check them anyway, and double check the PCV as well (which is connected to a catch can via -an lines).

For the reasons above, I'm fairly confident its the manifold runner flaps (which are normally controlled via an electric sensor and vacuum) since those are the only real change. The other thing is the car idles like if an idle air control valve gets stuck or fails, which is why I was thinking runner flaps. Also, the brake pedal softens a bit when I start the car, which leads me to think the booster is getting vacuum, so I should be able to rule that section out.

I'll still run through all the air / vacuum lines one more time to make sure, however, because I don't want to ignore a possible failure point. I'm also wondering if this could be caused if the fuel injectors aren't sealed properly. I removed and cleaned all of the injectors and installed new seals, but it's possible that extra air is getting in or fuel isn't because I did something wrong there.

Thanks for the help. I'll post some logs and let you all know what happens in about a week and a half when I get moved.

Hi Nick,

Having used several of those manifolds previously, I will say with a high confidence that the hunting issue you are experiencing is due to a manifold leak. The IE nameplate on the top of the plenum needs to seal, as it allows access to the plenum. The install of this manifold requires removal of a lot of auxiliary systems like runner flaps and a few other items, as well as a set of screw in barbs. Did you use teflon tape or liquid thread sealant with the installation of the barbs?

As Gord covered, the best way to rule out a leak is to use a flammable aerosol such as brake cleaner, and with the engine idling spray around hoses and mating surfaces to see if the engine picks up speed or the engine note changes.

Once you have thoroughly ruled out a mechanical influence, then you can look at tuning changes. The plenum on those manifolds is a significant increase in volume, so it may influence your symptoms a little bit. Showing us what settings you have available to adjust will help us provide feedback on how to make changes that will improve idle quality.

Nathan,

Thanks. I did use thread sealer on all of the plugs and barbs, as required on the install instructions. It is of course possible that I made a mistake. I also used a torque wrench on all of the bolts, including the ones for the plenum cover, but I'll check it all again.

For tuning changes, I'm really starting to think that adjusting the AFR at idle is probably the most appropriate. In the HP tuners software, I can go into the open loop settings after start and adjust the base lambda for a richer mixture. I do know that the car has the intake runner flaps closed at startup, which is why I was thinking that it had to do with that.

I was able to rule out vacuum as a source... or at least the vacuum lines from the vacuum pump. I'll check all the boost hoses again and do as you say around the intake manifold and the throttle body with some aerosol.

Thanks for your input, I appreciate it.

Thanks to everyone that responded. The good news is I found my issue and fixed it; it was relatively simple. When I replaced the cylinder head, I also replaced the intake cam adjuster valve, as the factory produced an updated one for my application. The updated factory one swaps the position of the wires at the connection, and evidently I failed to do that, even though I thought I did. Now the car idles at about 850-900 RPM with no misfires. The idle is a little rough, but I'm pretty sure getting it smoothed out is a matter of tuning.