My engine is going into some sort of failsafe mode. why??

[rwcoop]

I have this sti engine in my boat with the car ecu wiring etc so really it should be just the same as a car.
Every now and then it goes weird and im presuming its some sort of 'get home' mode. It wont let the revs come up anymore than about 1500rpm and then it cuts back to idle revs. Its hard to explain but it does it real quickly. A good description is it sounds like a rotary car idling with a loud exhaust. barm barm barm barm.
If i switch it off and back on again its fine for about another 30 mins or something. Any suggestions??

[Legacy777]

The only thing I can think of off the top of my head would be no speed sensor input into the ECU. The ECU will do some weird things if it does not get a speed sensor input.

[turboleg]

Could a bad knock sensor send it into limp mode? IIRC our EJ22's will do that if the knock sensor picks up knock or if the knock sensor isn't making proper contact with the block.

Not sure how the STI's work tho.....

[rwcoop]

mm, speed sensor. I doubt this would be it as this is the 3rd boat i have with a car ecu and it hasnt been an issue with them. Unless something is different with the sti engine, but i cant see how it would be any different.
And the knock sensor, well i could try and disconnect it i suppose and see if it does the same thing but im sure it just retards the engine when it detects faulty knock sensor. will try it anyway and really appreciate the answers
keep them coming

[Legacy777]

What year/model vehicle/ECU's were you using in your past & now present boat?

[turboleg]

Not sure of the effects of unhooking the wires. I think you might have to pull the sensor off the block. Unhooking it might make the ECU throw a knock code anyway.

Again I'm not 100% on that.

[rwcoop]

yeah thats what i mean. Ill disconnect the wire and see if it does its cuting out thing constantly. If so, ur right it will be the knock sensor????

[rwcoop]

hi josh. My last boat had a 92 gt legacy engine with the factory ecu also. It had the 4 plug computer.
My mates also running the same setup in his boat.
And now come to think of it, it was doing the same thing when i had the gt engine in this boat?? I have only jsut recently put the v2 (95) wrx sti engine in and does it every now and then.
Its a real distintive sound aye, sounds like a rev cut is coming in at 1500 or 2000rpm. sounds just like a boy racers rx7 with a big bore exhaust sitting at the lights in town.
if u come back to the idle it runs fine but wont go back to normal unless u kill the ignition.????
cheers for the tips. keep them coming

[Legacy777]

Next question for you would be, how do you have the ECU wired up? When you kill the ignition, does it kill all power to the ECU, or does the ECU still have a constant power source?

[rwcoop]

exactly the same as a car. The ecu has a constant power source unless you turn off the master switch which i dont do till the end of the day when im putting her to bed

[Legacy777]

hmmmm....then I'm not so sure....other then what I previously mentioned.