2G Random misfires when driving, goes away after turning ignition switch off and back on

[Jacob5se]

Hey guys,
After switching to a Prius COP setup, I’ve run into another problem.
While driving, the car will randomly start to misfire. The only way to fix it is to turn the ignition switch off and back on (usually it goes away after the first try).
It doesn’t matter whether the car is cold or hot, though everything is fine when it’s stationary (which is why I haven’t been able to determine whether it happens on one specific cylinder every time or if it’s random). Interestingly, it seems to be the worst during calm, low-RPM driving, like cruising down the highway, and “the best” when pushing it to the max.
The tachometer reads RPM properly, even while misfiring. I’ve tried swapping the coils around, but that didn’t change anything. They’re properly mounted to the engine using an Antilag Racing COP plate, and I built the harness myself using a write-up from the forums.
The car is tuned on a black box using Ceddy Mods. Nothing was changed after switching to the COP setup. However, the ECU was previously repaired — the transistor responsible for ignition on cylinders 1 and 4 was replaced because it had fried.
Any ideas on what to check? Running logs in Evoscan isn’t an option at the moment because I don’t have a Tactrix cable, and my tuner is about 3.5 hours away. My guess is that the ECU could still be bad and I should try another one, or that the ignition switch might be failing.
I might be able to record a video of the issue this coming weekend if that would help.

 

[jdxnc]

I'm not sure if it effects the black box ECU but on Ecmlink if you run a 1g cas on a 2g ecu it will do this with misfire detection enabled, the 1g cas doesn't offer enough resolution and the ecu thinks it's seeing a misfire and will disable a coil randomly during cruise, turning off this check stops it from happening. Perhaps its a similar situation.

 

[Jacob5se]

I'm not sure if it effects the black box ECU but on Ecmlink if you run a 1g cas on a 2g ecu it will do this with misfire detection enabled, the 1g cas doesn't offer enough resolution and the ecu thinks it's seeing a misfire and will disable a coil randomly during cruise, turning off this check stops it from happening. Perhaps its a similar situation.

I’ve seen info about this, I’ll check if something isn’t just loose near CAS, and will add checking if it’s enabled in ECU to the list of things to look at when I get my hands on Tactrix cable.

 

[Stapl3]

Matthais made 1296hp with stock coils, what are you trying to achieve here?

 

[Jacob5se]

Matthais made 1296hp with stock coils, what are you trying to achieve here?

Simplicity of ignition system and elimination of potential 25+ year old failure points. I’ve been having misfire problems before switching to COP so I decided to simple things up.

 

[We're on Boost]

I'm not sure if it effects the black box ECU but on Ecmlink if you run a 1g cas on a 2g ecu it will do this with misfire detection enabled, the 1g cas doesn't offer enough resolution and the ecu thinks it's seeing a misfire and will disable a coil randomly during cruise, turning off this check stops it from happening. Perhaps its a similar situation.

Is this 'cylinder misfire' checkbox what you are talking about? Just uncheck that one checkbox and it will prevent the ecu from sabotaging something just because it thinks there is a misfire?

You must be logged in to view this image or video.

 

[jdxnc]

Is this 'cylinder misfire' checkbox what you are talking about? Just uncheck that one checkbox and it will prevent the ecu from sabotaging something just because it thinks there is a misfire?

You must be logged in to view this image or video.

Exactly.

 

[Jacob5se]

Ok, so I ordered tactrix openport with Mitsubishi adapter. Will check if there's option like this in ECU, but Imo that would be weird as I have 2Gb CAS with 2Gb ECU. It should work just fine without gremlins like the one mentioned above when mixing things up.

 

[trogador2005]

Agreed, in ECUFlash you need to change the random misfire check DTC from a 1 to a 0

 

[Jacob5se]

Agreed, in ECUFlash you need to change the random misfire check DTC from a 1 to a 0

Thanks for confirming there's this option in ECUFlash, I will see if it resolves my problem. Thank you for your suggestions guys, I'm looking forward to hearing some more suggestions on what to check and what can cause this.

 

[Jacob5se]

Time for update
I was able to go to my local tuner and switched off random misfire detection as you guys suggested. Everything works fine now, no misfires etc. Thanks a lot everyone!
For those that might be looking into this thread in the future, you'll find it in the Periphery section of your ROM. Then open ECU Periphery2 Bits and set both bit.04 and bit.05 to 0.

You must be logged in to view this image or video.