rb20det cold start issues

[Mikea93]

Hi everyone. Ive got a skyline hcr32 , i have the stock rb20det engine.

When i first start the car it has a hard time keeping idle and sometime drop really low, as low as 100 rpm, unless i give it gas to help it. After 20-30 seconds the idle stabilize but if i give it throttle it will missfire and bug down (wont boost at all), if i insist ill hear a popping sound that i suspect is coming from the intake.If i go in gear, It wont accelerate properly until i hit 2700ish rpm at which point it will all of a sudden rev and boost normaly.

This problem occur only when the car is cold, and settle as soon as the engine get to the running temp.

Please help !

Changed Maf and Ecu
New IAC ,front 02 sensor and Spark plug.
Coil have been tested

[Skym]

ECU tune.

That starting problem is normal after changing exhaust. It's the start up tables on ECU that need to be retuned (fit Nistune, retune ECU). You can crank engine longer (to get pistons sucking more air into cylinders) and then let go of key and it should start fairly normally.

Sometimes the starting problem is worse when there's a intake airleak (loose intake hose clamps). Sometimes the AACV and IACV are dirty / sticky due to oil in blowby gas that gets into the valves (service related problem).

Driving problem is normal and is ECU pulling ignition timing, running engine rich (to protect engine when cold). If rev over 3000rpm or go past certain coolant temp ECU stops pulling ingition timing, etc.

[Mikea93]

Great i happen to have nistune , got one a little while ago after reading one of your post actualy :P
Ill try this , it seem like it would make sense , my ecu/nistune was in a 240sx rb20det swap before, the tune might have been a little different to what my car need.

Thank you Skym, you are the best!