E46Fanatics - View Single Post - E46 M3 AA Stage 2 - Issues With Idle After ECU Update
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Old 10-20-2012, 05:38 PM   #22
Registered User
Join Date: May 2009
Location: Utah
Posts: 72
My Ride: 05 M3 Vert
Man, I'm really getting frustrated. HPF with an AEM is sounding pretty damn good right about now.

I rigged up a system to pressure test my engine in lieu of a smoke machine (didn't want to wait for my friend to come up next weekend). I pressurized my system and fixed what could have been a minor boost leak - but probably not a vacuum leak. Now everything is solid under pressure. No leaks of any kind. Didn't make a bit of difference. I pull 15 in/Hg at cold idle. That seems rather low; but I think that may be an effect of the altitude (5500ft ish)?

I haven't gotten my wide band yet, but Epic's post sounds so close to mine I wouldn't be surprised if his readings are the same as mine. I think the only reason the 1.5 tune idles is because it's REALLY rich at idle.

In logging the OBD2 data from my car (PLX Kiwi FTW) - I observe my short term fuel trims are pretty high at idle. 25-40% positive fuel trim on all four banks. I noticed my fuel pressure was high at idle (50psi) and I was getting short term fuel trims in the 20-30% range. After I adjusted it to the spec'd 42psi I get the higher fuel trims as expected (needs to add even more fuel). It's also odd to watch my O2 voltages. They go from really lean to really rich - not much in the middle. Something is making dramatic knee-jerk corrections.

Now, as I understand it - this is usually indicative of a vacuum leak. This is because more air is entering the system than the ECU is anticipating and the O2 sensor reading is lean. So the ECU adds more fuel (via short term fuel trim) to attempt to correct this lean condition.

I'm REALLY sure I don't have a leak of any kind. A nice snapon smoke machine and my pressure test are pretty conclusive. So, either one of two things is happening - more air is coming in than the tune anticipates OR the tune is just really crappy and not delivering enough fuel given the larger injectors (could be altitude but I'm sure people with Stage 2 kits live in Denver and other high elevation places).

Now, as a logical person, I'm trying to think that if Active had this problem a lot in their Stage 2 kits we'd hear about it. But, I bet they sell a lot of Stage 1 and Stage 2 kit's - and perhaps even some Stage 1 - Stage 2 upgrades - and not as many Stage 1.5 -> 2 upgrade "kits". I'm guessing the issue is here somewhere. They send something or something is different when you get a full Stage 2 kit vs the Stage 1.5 upgrade.

I went from a Gen 6 Stage 1.5 kit to a Gen 7 Stage 2 kit. This included the new fuel system (fuel rail, lines, inline fuel pump), meth system, pully, larger injectors, and a new "log style" intake manifold. I took my bypass valves off my old square Gen 6 manifold and put them on the new one.

The only theory I have now is those bypass valves. I'm running a much smaller pulley on that supercharger now and it's positively pressurizing the intake a bit more than it used too (I assume). If those bypass valves are still setup for X (from the 1.5) - could I be over-over pressuring the manifold and adding more air than it anticipates? Other than that, I can only assume a bad base tune. Ugh.

What else could go wrong or be missed when you go from 1.5->2 instead of starting at 2 or going from 1-2? I'm on my 6th idle correction tune with no real difference (the ECU still has to add up to 40% fuel).
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