I have a 93 civic that has recently had the bottom end rebuilt, put everything back together and it ran but something wasn't right. Turns out #3 cylinder isn't firing well I switched 2 and 3 injector plugs to see if it was the injector itself or the plug. Well #3 fired but #2 didn't ok so its not the injector so I switched them back and now they both won't fire. I checked the main relay and its good, they seem to not be getting a ground. So if anyone can help me out I would appreciate it thanks.

 

You would normally switch the injectors not the injector plugs for this test as you will have 2 cylinders misfiring.

1) Check whether the #2 and #3 injector plugs get voltage with the key in ON(II).

2) Check the #2 and #3 ground wires that run to the ECU for a short or open.

 

Ok I will do that, I also opened the ecu today and q31 is fried what could that mean.

 

Evap purge and IAT plugs are backwards. Its pretty simple to repair the board.

 

Is this the likely cause of the injector pulse problem?

 

Nope. first thing I would check there is the 4 wire shock tower plug on the passenger's side shock tower. All 4 injector signal wires go through this plug. Check to make sure its plugged in properly and that the pins all look good inside.

 

Ok the iat sensor and purge were in the wrong plugs so I switched them, the iat sensor wasn't burnt thank god. The injectors still won't fire and I have tested the plugs traced back every wire from the injectors, everything is fine. Oh and the 4 wire shock tower plug is in perfect condition. Let me add though I'm not so sure the ecu can be repaired because q31 is almost melted clear through the board and burned a bit around it too.

 

Did you check for voltage at the Yel/Blk wire terminal of the injector connectors?

Did you test the injector ground wires for continuity or a short?