Request for New Eyes on Mega Log from Tuner Studio

[Drscottsmith]

All -

Can someone with a little more tuning experience than me help me with a couple of issues related to my latest tuning log?
About 300 seconds into this, the car stalls while driving. I am not sure what is causing it as things just kind of go crazy at that point in the log.

The car has been doing this lately about once or twice per drive. As I am coasting, I can restart the car and everything will be fine.

Im not sure if it is a voltage issue causing MS to crash, a fuel problem, or what. This entire drive was on the way home from work today and there is another stall a bit later with the same result. So just trying to piece this story together.

Thanks for looking and sharing the expertise!
This is my 1986 951 unmodified exceot for the MS setup and required sensors, etc for that.

-scott

[Tom]

I'll add this to the newsletter to see if we can coax some MS users out of the woodworks....

[cda951]

I think I have MS on my work laptop from a past customer project, I will look tomorrow if I have time.

Ping me here if you have not heard from me after a couple of days.

[Drscottsmith]

Hey Tom and Chris thank you!

A response to my cross post indicates a reset each time of the MS controller. I’ve got to do some investigating. I have lately been messing with accel enrichment, but have always seen a voltage drop at the gauge when the cooling fans kick on. I don’t think the reset is happening at the exact same time but will have to check that.

I’ll keep this thread updated but please let me know if you see anything odd. I don’t think I have AE set quite right yet so would appreciate any comments there as well.

Thanks again!

[Bergerac]

Seems to be quite a few occassions where you MAP sensor is dropping to basically 0 which is dropping you off the bottom of your fuel map. (Injectors duty cycle goes through the floor). No way that should be happening at 2000rpm. Why is your Idle valve cycling like that?

Screenshot 2026-07-27 204441.png (88.4 KiB) Viewed 26 times

[dr bob]

Hi Scott --

Amateur outsider non-944 owner here.

On similar installations, your symptom has shown up when the controller ground is to chassis rather than the block. Ideally, that single clean shiny ground point on the engine would include the controller itself, injectors (via that controller ground), and any engine-mounted sensors that don't ground directly to the block.

You can inspect the battery ground to chassis and the engine to chassis cable, but my advice after some extended testing and troubleshooting that is to just replace them with new.

Consider adding dedicated feeders for the cooling fan(s) directly from battery + to the relay and controllers. This will let the battery 'soak up' the starting current inrush without having to wait for the alternator to react with more current


I endlessly preach about maintaining excellent primary cable and ground connections at the battery. Clean, shiny, new looking. There's an Annual Electrical Maintenance protocol that includes inspection and cleaning of all ground points in the car, the primary cables and connections, and an easy test of battery condition via a specific-gravity test of the the electrolyte fluid (read: acid). A little cheap parts-store floating-balls tester is perfect for this.

Hope this offers you some help!


Bob