Originally Posted by RobbieOh

Since my tune two years ago, my AFR has been all over the place. WOT it can drop down to 9.8 and I've watched it spike up to 18+. I don't daily the car, and when I do drive it, I've been driving like a grandma to try and keep the AFR where it needs to be.

I was wondering if anyone had any input or would be able to look at any logs to see if they can figure out what's going on with my AFR. I know it's running pretty rich because I'll get huge black clouds on hard acceleration.

I'll list the build and see if anyone has any input. Any help would be greatly appreciated.

2014 Evo X 60k Miles
413whp tuned on 93 octane. No e85 yet.
AMS CAI
Grimmspeed boost controller
ID1050x Injectors
Walbro 450
Garrett 3576r
MAP tubular exhaust manifold
AMS Downpipe
ETS Catted Test Pipe
ETS Ti single exit exhaust
Exedy Twin Clutch

Originally Posted by RobbieOh

Yes, bc your original post is showing up with white text that is the same color as the background. Does it not look like that for you?

Originally Posted by Lightsaber

Could it be a mechanical failure, like the 3-port is acting up?

Originally Posted by adi105

So I am having an odd idle (and cruise) issue, where my AFRs will fluctuate very rapidly. Here are the main details:

• Fresh head rebuild. I am only 400 miles on it so far. New intake valves, it has gsc s2 cams and beehive springs
• I am tuning with Christian Muna at Pure Drive Performance in Colorado. We are not doing any power tuning yet until I break in the new valves, etc. We are just trying to do the MAF and MAP calibrations. As of right now, he has only done one adjustment.
• It has an MHI 18k turbo mated to the MAP investment cast manifold. ID 1300 injectors, AEM 320 fuel pump, full bolt ons basically. Just listing the mods that might be relevant to tracking down this issue. My intake is an ETS intake with a stock maf and maf housing, and my BOV is a Turbosmart Dual Port with the softer spring installed.

Originally Posted by adi105

Yep! This deserves a followup. I had a fat exhaust leak between my manifold and turbo. This caused crazy AFR jumps. After changing this and confirming that there was no longer an exhaust leak, resetting my fuel trims via the fuse, and some MAF/MAP adjustments, it is now idling and cruising right around stoich.
Christian is a great tuner and the fuel trims on this thing are spot-on now!

Originally Posted by Lightsaber

Then I suspect it's a bad tune, for instance the MAP/MAF tuning has been done inappropriately.

Another possibility is an exhaust leak, such as the factory design's double MR187848 washers were not used on turbo-to-manifold bolts. A exhaust leak there combined with an aftermarket turbo can cause rapid AFP fluctuations. ​​​​​adi105 , another Evo X owner, had this problem a few year ago: