Fuel Cut out problem, overboosting?
 

Hi Guys


I just recently got a 2005 5spd JDM legacy 5pd GT turbo (BP5)


The car has a downpipe (little leaks in the downpipe and exhaust), and surely the ECU has been tuned. I am not sure what the ECU is doing or what boost is running.
The car pulls much harder than all other factory 5pd GT turbos I tested. and the Boost comes up much sooner.


However, when I pull hard in 1st gear, the fuel cuts out all the sudden. the car goes into Rough Idel (up and down), and will not reset itself. I can bearly nursing it to the roadside.


If I turn OFF the Ignition and wait for 30 seconds, then the car comes back fine again.


I didn't catch any error codes when it happened ( I was trying to put the car in a safe place)


Any ideas? Factory overboosting protection?

Assuming the JDM ECU has the same protection as EUR and US, then yes it could be that it's overboosting with the (assuming decatted?) downpipe, and cutting the fuel.

On my UK Hawk when I hit the boost fuel cut threshold it drops out fueling briefly and puts the MIL on, but the car drives normally immediately afterwards, even with the MIL on - so it's slightly different to what you report, but that could be a difference of the ECU logic. Might be worth using a cheap OBD tool to see if any codes are live. I would imagine an error code relating to the wastegate solenoid would be either live or past.

Yes its decat fully and after market exhsust etc. Sorry i am very new to this, how do i check the code? Also i am planning to get the ecu reset to factory, as i am very certain the power is too much for the car and engine. How hard is this? I am guessing is a specialised job or could any mechanic do it?

laptop, lead and do some logging, see what boost you are achieving.