So I swapped a b18c jdm long block in my em1 with stock harness. Did the ckf trick.. Connected everything else and went to start the car. It would start and idle for 2-3 seconds and then shut off. Any idea, what the problem could be. Thanks for the information.

 

CEL codes?

What ECU?

 

No cel. P72

 

OBD1 or OBD2 P72?

Does the CEL work?

 

Obd2 p72 and yeah the cel does work. Engine is also obd2

 

Are you able to keep the engine running with starting fluid?

Are the ignition system components well maintained?

What's the spark quality? Plug wires installed in correct firing order?

Is the mechanical timing off by a tooth?

 

My mechanic says the car stays running if he keeps spraying starter fluid in, and everything else is in check.

 

You have a fuel issue. Could be low fuel pressure or the injectors aren't working.

 

Thank you.

 

I'm not going to say for sure this is your issue, but something to look at. I did a head gasket on a Kia and put everything back together and had this very same issue. It turns out that there were two connectors on the throttle body that were identical and I had them going to the wrong sensors. I swapped them around and the issue was gone. Again, I am not sure what is under your particular hood but if two sensors have the same connector style it is possible that in the swap they got reversed.

 

If you still have the original p2t, put it in and see if your car stays running. If it does than your jumper harness is probably the issue.