Jgilby

I recently came upon an issue with my ms3pro on my 92 Miata. When I turn the key to the on position, Megasquirt reads the Map at 100. There is another issue, but I'm not sure if it is related or not, which is that at initial idle the car will run for a few seconds and then die. The only way to keep the car alive is to hold the throttle partially open. Even with the throttle slightly open the car will cycle between 750 to 3000 rpm with the AFR going from around 10.0 to 22.4. While this is happening, my fuel pump relay is making a buzzing sound whenever the AFR starts to rise towards 22.4. *NOTE* The fuel pump relay will buzz for around 3 seconds as soon as the key is at the on position. The relay looks fine on the inside, there is no corrosion and/or broken pieces. This might explain why it goes super lean (cutting fuel altogether) but I don't know if it's related to the map of 100 Kpa at key on issue. Below is a datalog with the car driving around town before the issue and a datalog on the car at a standstill in my garage with the current issues. Does anybody know if it could be a wiring issue or maybe the ecu is bad since the ecu reads map pressure. I would appreciate any help anybody has to offer.

vtbandit

100kpa is atmospheric pressure so the ecu is just telling you you’re on earth. It is a good thing at initial power that it reads that.

Skamba

100 kPa when the engine is not running is normal. That is atmospheric pressure.

Did the car ever run correctly? The logs look like an untuned car to me.

Jgilby

Ok I guess I was overthinking it. That makes sense since there is no vacuum. The car did run properly for around a month which is how long its been since I had a professional tune it, (national speed NC), apart from the issue where the car would go to full 22.4 afr when the throttle was all the way out. The during cruising it would be super annoying because the car would sort of jolt due to a lack of power. I will drop a datalog with this issue present. My theory is that the fuel pump relay is bad but I just tested the resistance and it showed 144 oms. maybe the wiring is shorting out somewhere. The kick is that when the tps is at 0 then this fuel cut issue is present. No, Over Run Fuel Cut, is not on. I am under the impression that somewhere in the wiring for tps and or the fuel system, there is a short of some kind.

Jgilby

After cleaning the ground for the relay, the white/clear box of grounds underneath the brake booster, the relay will still buzz when the key is on the on position but the car will run by itself and drive down the road 100% better than before. It did, however, short out after another start but a little throttle solved that. I will clean the inside of the little white box instead of the main ground and see what happens.