So i just finished swapping a 02 wrx (engine, all wiring, trans.. everything) in to a 02 impreza.  

The WRX was wrecked beyond repair but still ran , shifted, moved etc. The 02 impreza had a blown engine but was rust free

When I went to start the car after the swap it sounds like a car that the timing is off. 

It cranks then has a distinct lag, no backfire though then cranks normal again.

Doesn't "lag" everytime but 9/10 times it does

Similar to when you install the wrong crank gear/ cam gears on the 2.5 sohc.

Any ideas where to start?

Edited January 3, 201610 yr by logic23

CEL on? scan for codes - could be in 'limp' mode?

Battery fully charged? 

 

Wrong timing gears? 

Make sure all the engine and chassis ground connections were connected as they should be. A number of folks have had troubles due to that when making changes like you did.

wonder how long it sat? how old the timing belt and rollers are?

 

you might consider inspecting for slipped timing, and dropping the exhaust to look for 'dropped' valve guides.

 

Thanks all for your help.

There were 2 issues going on: stuck tumbler valve(drivers side) and i had the coil pack wires switched on the passengers side. 

The stuck tumbler valve was putting it in LIMP mode. Once i replaced the bad tumbler valve postiton sensor ( front of engine) the valve opens and closes and no code

Then the car tried to run and I got cylinder missfire codes. Checked the injectors and coils. thats when i discovered that I put the wires on backwards. 

She now purrs like a kitten. Should have this on the road soon. 

its a 2001 wrx with 103K into a soild no rust impreza outback with 278K on the body.  upgraded to 04 larger front brakes. tein coilovers.  Ill take some pics when shes all buttoned up. 

Thanks again crew

needs timing belt service.

I did the timing belt, water pump and all 4 tensioners while the engine was out..