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Getting a Lean Blip Nat Asp 1.8L Miata running SpeedyEfi Standalone, Tunerstudios / Megalogviewer

Practical Standalone Tuning

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Hi HP guys / gals.

Lean Blip I'm trying to Diagnose and tune out!!! 4700-5200 a blip or two on WOT .

1994 Miata 1.8L USDM Full Exhaust (header as well), Running Speed density tuning model, no MAF, IAT added, and MAP sensor added.

SpeedyEFI Ecu A Arduino / Speeduino DIY style, BUT it is a Plug N Play version MADE for my application , ECU harness connectors are stock, as it is PNP.

Runs good, except for this Lean Blip I'm trying to Diagnose and tune out!!! 4700-5200 a blip or two on WOT .

I've been trying to road tune out this lean blip I keep getting at 4800-5200 rpms. It's Like without a doubt some kind of misfire-like in feel.

What I've tried:

1.) *mechanically* a different set of coils, plugs and wires.

2.) Logged the trigger tooth logger and Well IDK how to look at that, but it looks smooth?

3.) I have tried to richen that one point and the surrounding cells No help.

4.) I have tried playing with Accel Enrichment and EGO settings to see if I can get it to just ignore the EGO, but I'm not sure If I have that going right..

I can upload a Current Tune and a Datalog for anyone who has MegalogViewer and Tunerstudios to look at?

But also any ideas are greatly appreciated.



The Lean spike you see in your data is what a typical misfire looks like. So I think you are chasing a misfire. Do not change the fuel map attempting to fix this. The best thing you can do is to find a condition that makes it consistently occur. Only then will you know if you have fixed it. I would be looking for a wiring issue (normally at the connectors for the coils or injectors). You say you've replaced those, but have you tried wiggling them individually while at speed faster than idle (say 2500 RPM - half the RPM where you see problems).

If it really only happens in a particular RPM range, then I would look for issues with the trigger wiring.

Hope you find it -- these things can be frustrating!

Hey Dave,

Thanks for chiming in. I have resolved the issue. It was an Unknown Cam Angle Sensor (The early gen Miata's CKP and CMP Trigger all in one). It was sourced during the period I could not get the engine fired up, but it was not mechanical at that time, it was settings. But The car started and ran, so I left whatever was in there in there.

Lesson learned, using "previously Loved" parts that are around are not good for the long, but maybe for testing. But I went back to my car's original running fine Cam Angle Sensor and All is well!

Now I need to fine tune my Acceleration enrichment, Warm up enrichment / heat soak issues, and get the car not to stall when the A/C is commanded at idle (Street Car).

Any help is greatly appreciated! Links to how to, ect.

Great work, and thank you for posting the follow up with how the issue was resolved!

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