Forbito

My theory is: the PWM transistor probably blown quite soon after the first installation, and this would explain why the valve did never work, manteining the idle costantly high, at about 1400rpm. I would have done better to check first to understand the reason of this, but I had postponed the inspection to after the race (I never have enough time!), focusing on tuning and keeping the valve blocked once the engine was warm. The car ran perfectly until the race. Then, the death of the MS1 has been caused by something else, almost certainly an internal failure (because the ECU remains off and doesn't communicate despite that there is not any interruption in the power supply and in the ground wire). It's not clear if it depends on the burning of the PWM transistor or not. The failure seemed to occur progressively: first difficult startings, but once the engine was running any malfunctioning disappeared, then it died during the race and without any warning. This could be a clue, but I have no idea on how to interpret it.

Ok, thanks for your help. The power source of PWM valve was protected by a fuse, but it was evidently too large. But my doubt is: can the failure of PWM circuit, alone, make the ECU unable to run?

This has just happened during a competition, about 250 miles after installation. The engine had begun to have difficult starts a couple of hours before, the ECU activated the pump relay intermittently and I was able to start it only at the second attempt. The wiring loom has been correctly built, everything ran well until disaster... The ECU has been always protected by a 3 amp fuse. The blown transistor is the Q16 and if I understand correctly it is the only component that drives high current. Apparently any other component in the MS1 board is damaged, so it could be easely replaced. But I would like to understand what went wrong and avoid to meet up with another blown transistor after a couple of days... Is there something that I have to check considering the internal damage?

Clear, in fact I would like to obtain a stable warm idle of about 850 rpm. The problem is that the valve can not even mantein anything lower than 1300 rpm. However all the settings are fine.

Sorry badly written. I always cap the valve completely when tuning (the base idle si adjusted to 800rpm). Now the map is becoming to be quite good, but the PWM doesn't seem to work properly. In warmup mode the valve remains always fully open and in closed loop it varies the engine speed only when you edit a parameter (for example putting "800" instead of "850" in warm idle) and as soon as you touch the throttle the tickover returns high. I want to try to put a diode in the wiring to see what happens.

Now I'm working on the VE table using an LC-2 wideband lambda. I had to lean quite a lot the map especially on the lower-left side of the table (I have been careful to proceed with the tuning phase only once the engine was warm and PWM plugged, without any TPS enrichement).

A trivial stupid error in the wiring Now I have a perfect reading of the air temperature, but the coolant temp is a bit high (shows 21°C when it should be about 15°C). The next step is to gain a good tickover.

Okay, I opened this topic too soon, problem solved! Now I'm starting the tuning process, the engine runs very rich and with high tickover. As soon as I will ultimate the wiring loom (now it is still uncovered), I will post some pics of my installation

Hello everyone, I'm writing from Italy and I'm new in this forum, but I have already learned a lot here about Megasquirt. I bought a complete kit from Nigel (before I used Megajolt). The vehicle is a 1990 Land Rover 110 3.9, manual transmission. Yesterday I completed the wiring harness and I connected everything to try the first starting. The engine runs and all the readings are correct, except the manifold air temperature. The ECU reads -40° C, so the engine runs very rich to compensate the distorted value. This is the screen shown by Tunerstudio: The MAT sensor is a new AT1010, so it's not a problem of calibration. What may I do to solve the issue?