So today randomly after pricing out some tires, it was warm, sat for about 25 mins, then i went out and shortly after, it started to have a shity idle. It has gone more lean, it's off the chart at idle now(18afr+) and it sounds like it's cammed. shaking and shit. NOW what... I didn't change anything.

Is it possible it's my fuel filter? I show pressure up to and beyond 40psi, but i'm not sure if that's a guarantee the fuel filter isn't holding it back. I'm trying to figure out why it wants to stay lean. What else could it be? I have a walbro 255 to put in but like i said, I can get probably 55psi maybe 60 and that's it. Only cranked it up to see how the 12v mod effected it.

If your AEM has a narrowband output Try disconnecting the stock sensor and run the AEM narrowband output to the ECU. Wideband AFR's aren't "off the scale" until they hit about 22... A limitation of your wideband perhaps?

No, it's not your fuel filter or pump... You'd have MUCH bigger problems under a load than when you're at idle.

Part throttle boosting often involves the throttle still being open at a low enough angle that the ECU is still in closed loop operation and adjusting the fueling trying for 14.7:1. Check that this isn't the case. If it is then yeah, the cloud is probably extra fuel from the sudden surge when you finally stomp on it and the ECU goes into open loop.

You've tuned your fuel pressure while at idle with the vacuum disconnected? What pressure are you running presently?

I'd start looking for that noise in hardcore mode... Noise isn't good. Especially if you were running lean while booting and didn't catch it (been there, done that, replaced pistons).

What are all of the settings you're running now?

Relatively new AEM wideband, sensor mounted in the correct spot/position. Just for the record.


Yes, vacuum disconnected, running 40psi. Any less and it wouldn't say below 18afr('off aem gauge scale'). BUT now it is staying above 18 at idle, no matter the fuel pressure.

As for the noise, I didn't hear it other than those first 2 times, 1 was with the boost controller setup shity, so it spiked, but did not go lean. (looked at wideband gauge when i heard the noise). Other time also not lean, but with the boost controler setup properly, at 17psi, but with a preload on the turbo then stomped on it, it may have boost spiked but it didn't go lean so i'm not worried about the pistons at this point, although i do want to do a compression test just to rule any of that out.


Settings as in for what?
-Greddy profec b 2 is setup to boost to and hold 17psi (no spiking or creeping or dropoff after an hour or so of tuning it)
-NEO is setup for 0+/- across the board but also turned compensation off, so no fuel compensation but naturally it's still rich in boost with the 550's + lex afm.
-Fuel pressure 40psi (no vacuum, at idle)(also has 12v direct relay mod)
-ECU was reset when i initially installed the lex afm(about 6days ago, i haven't driven it the past 3 days)

Oh, I assumed you'd started working with the NEO now. Increase the fuel of the low load map from the first set point up to the 800RPM cells in 5% increments. See where that takes things and then worry about the fine adjustment after you get close to the desired results.

I didn't realize you also had an EBC in there. Personally, I'd disconnect it and tune the system for stock boost first.... but that's not a significant concern if you've already got it set up and running properly.

Well I intend to run 17psi so I want to tune for 17psi.

And i've been told by many not to touch the low throttle input for the neo, letting the ecu handle that, instead of having the ecu fight my adjustments, and just tune hi throttle.

Either way, that's not my issue, my issue is ONLY my lean idle, and lean cruise.

Compression test = Check.
Boost leak test, 25psi = Check.
Different afm test = check(no difference)
AFM cleaned = Check(no change)

Found a small vacuum line that feeds the boost control had blown off the manifold, that's why the idle was shit after I left the mechanic and did a pull, blew it right off. Car is new to 17psi so there's one thing checked off. Ruffed up the fitting and zipped tied, Check.

I notice randomly it sometimes has a good idle, 15ish, max 16. Then other times it sits 16.9-17.9.

Also I have not heard that noise more than those first 2 times.

Tune the low maps so the ECU isn't working too hard to get the proper AFR. Also, you need to tune the low and mid maps to get somewhere close to 14.7:1 as the ECU isn't always in closed loop in those ranges. You can't stray much from what the ECU wants the AFR to be at in the low and mid maps but yes, you need to tune them all. For the high loads (about 70% throttle or more) you can tune for whatever AFR you like. My preference is to tune the mechanical hardware to get as close as possible across the whole spectrum and then us the fuel controller to fine tune everything. Try unplugging the stock O2 sensor feed to the ECU (forcing the ECU into full time open loop mode), tune after a cold start, aim for 13.5ish for the low map and 14.5ish for the mids, reconnect the O2 sensor.

Do NOT try to clean the AFM. You can blow the honeycomb out with some compressed air but NO cleaning solutions or solvents. The sensor is optical and if the cleaner enters the sensor or fogs the lens the entire thing may be ruined or way out of whack.