Strange NB cold starting behavior.
 

I recently installed a JDM BP5A engine and transmission into my 2000 to replace the 276k mile mill. The engine was advertised as ~30k miles, and looking under the valve cover and into the lower intake manifold I see no reason to doubt that claim. While the engine was out I locked the cams together at TDC and changed the timing belt and idlers. I spun the engine 4-5 times completely to verify timing and reassembled. The car is a 2000 california emissions SE originally.

I installed the engine with the following modifications:
BP5A ECU
RB header
1.6L clutch/flywheel
Skunk2 throttle body
port matched upper intake manifold (VICS)
EGR delete
K&N intake thingy
M-tuned reroute
removed fender mounted fuel pulsation damper
Replaced primary cat (in midpipe) with spun metallic magnaflow unit

The following parts have been replaced:
Fuel pump - Walbro 190HP
VICS solenoid
plugs - NGK
wires - NGK
all the gaskets I touched including mains
camshaft sensor
ECT sensor (also verified wiring good)


Since replacing the engine, I have had a strange cold start issue. I can crank it fine and it fires on the 2nd or 3rd crank, but suddenly dies. If you push the throttle open and hold it while cranking, it will start, but runs on maybe 2 cylinders for about 10 seconds. After about 10 seconds of throttle holding, it will idle and run fine. If the car sits for under 2 hours or so, it starts perfectly.

If you start and hold the throttle to clear up the idle, start driving down the road and a couple of block away shut the engine off and restart, it still barely starts and required holding the throttle down for a bit to clear up. It seems like it is either fuel fouled or the rail pressure is low, but if it was rail pressure the car would fire properly after being driven a couple of blocks.

This problem was present before replacing the fuel pump, ect and camshaft position sensors. Those were done in an attempt to correct this.

I cannot verify live data like engine coolant temp and MAF frequency because the BP5A computer has no OBD functionality, and prior to installing it my OBD port was powered but not communicating with the scan tool.

The car runs decent enough when warm, but I feel like it may still be a bit down on power. After changing the pump it seems better than it was, but still doesn't feel any stronger than a stock miata. It has a slight hesitation off idle when stabbing the gas, but I have not installed a wideband yet to confirm if the hesitation is fuel related.

The other caveat is that concealer404 has an almost identically built car that exhibits none of this.

Also, the fuel injectors were flow and leak tested before I installed the engine.

Anyone have any ideas?

Does the BP5A ECU control vics?

Maybe leaky/screwy FPR, letting the fuel rail loose pressure after priming.

Yes the BP5A has and controls VICS.

If the FPR was bad, wouldn't it start fine after the idle clears up the first time? Wouldn't it have built pressure back up by then? I ordered a stock replacement FPR just so I can eliminate it as a possibility.

I also checked the cam timing, it's perfect.

It seems either the crank sensor or the fuel pressure regulator was at fault. I changed both and it starts and runs a lot better.

The engine I got from the junkyard had 60k and the head was warped and needed a valve job :( hopefully yours is healthy enough.

That's an opportunity! PORT

Were you racing to the gas station in that video?

Sending unit was being weird. It was fixed later that day!