Loose electrical connection under intake?

[keltik]

Hey guys. Vehicle is a 1989 Legacy GT, motor is a EJ20T but the wiring is very similar to the EJ22's you all know and love.

 

On my drive to Auckland a couple weeks ago the engine decided to cut out on me....several times. Each time it presented with the same symptoms:

 

Engine would crank fine but would not even attempt to fire.

Check engine light would NOT be illuminated with ignition on

Coolant temp gauge would be pegged on HOT

With ignition off there would be a faint glow from the oil pressure and charge idiot lights

Idle control valve would not make the humming it usually does with ignition on

 

After wiggling the main bit of wiring (runs from the 3 terminals near the battery and powers coil packs, injectors, temp sensors and TPS) that runs under the Intake manifold, the car would fire and start easily. However im assuming the vibration of driving would knock this wire loose and the engine would cut out again.

 

I eventually fixed it by duct taping the wire to the nearest thing (intercooler water pipe) so it couldnt move and this fixed my problem. The car continues to run fine.

 

Whats the likely culprit for this? I know its going to be a loose wire or ground but rather than remove the intake to find it - id love to know which connection could be affecting the ECU like this.

Are there any ECU power connections or grounds under there?

 

When i had the intake off last i plugged everything back in as it should be but its totally possible one has worked loose. I just need to know which one as all still seem to be connected.

 

Thanks for any help.

[Legacy777]

It's hard to say. There is a sensor ground on the intake manifold. I'd be suspicious about the coolant temp sensor since it was pegged hot.

 

That may be a good starting point.