Calling all Miata troubleshooting gods - NA8/NB1/MS3 Content Inside
 

I need some assistance after I feel I’ve exhausted all of my experience. Crossposted from the FB group as it petered out.

1997 Miata, NB1 engine (NA), MSLabs Megasquirt MS3 Basic (Trackspeed), LS2 coils, NB2 injectors (cleaned/balanced by InjectorRX July ‘19)..

Backstory: Car was tuned by a pro and ran great at Road Atlanta back in August, but has sat since. Swapped on a Skunk2 TB to prevent the ingestion of TB screws and the car wouldn’t idle. Thinking it needed a bit of tuning, I poked around MS and tried adjusting the IACV in test mode to get it stable. No response no matter the PWM% selected. IACV apparently dead. Opened ECU to find 6A fuse was blown and IACV copper trace was burned and continuity was broken. I replaced fuse, repaired trace, and confirmed continuity was restored. IACV still unresponsive and would idle to the moon when plugged in and started (stuck open/fried internals probably caused trace to burn). Unplugged IACV and cracked the TB screw to set mechanical idle at 1,100. Now idling fine are 13.4:1 AFR. Go for a test drive and find severe bucking/missing at load under 5k RPM. MTX-L shows ~9.8:1 AFR. Here’s the kicker, the car cleans up and revs fine above 5k.

Bad coil would cause lean reading due to unburned air as well as fuel. Changed them out anyways to no avail. Changed spark plugs, no change. Tested each coil and injector in test modes via MS and each was receiving signal, so ECU to component is good. Changed back to stock TB, no change. Multiple tuners looked at data and couldn’t figure out why it’s running rich and breaking up in the mid range, but cleaning up on the top end (albeit staying rich).

Thoughts? Clogged injector (unlikely)? Fried injector drivers somehow? Let me know if you’d like more information. Am I dumb? 🤦🏻‍♂️

Datalog (Startup, idle, light throttle, heavy throttle in 1st and 2nd, light throttle, idle): https://drive.google.com/file/d/1La2...6XR_tJbJUH0cxU

Bump. Have emailed Reverant, but haven't heard back. This young MS padawan needs some guidance..

Whenever your issue happens, the injector pulsewidth I see is around 14-15ms, which is quite a lot. Please attach your tune as well.

Just getting back from out of town. Thanks, Rev. Attached.

@Reverant Posted tune file.