I just have swapped my 390cc DSMs to blue top 450cc injectors. Since then my idle is not stable, it falls under 500rpm and then goes up to 1000rpm. Sometimes it is ok (750rpm). It happens not only at cold startup, but even at warm engine. I use SMC500. I tried to set idle at -35%, -40%, but no luck. I can not get rid of moving idle.
I also checked for leaking around fuerl rail, leaking at injector rings, but everything is ok.
Does that 60cc diff between 390cc and 450cc mean so much at idle?

 

Have you adjusted your AF ratio to try and lean out those 450's a bit more to match where your 390's were running? Any wideband to use as a refference?

 

Sure i adjusted my A/F ratio (-5% at all rpm). It runs fine, but idles bad now.

Unfortunately I have no W/B lambda.

 

You need to take more out at idle do to injector latency.

 

I remember having to go as far as -50% at idle to get a decent idle with the AFC and 450cc.