Bart-Jan

At idle, my engine rev's are dancing up and down from, say 700 - 1300 rpm both in cold and hot state. I initially adjusted idle speed with the bypass screw on the throttle body, which is screwed in almost all the way. When I press the throttle a tiny little bit, it stays constant at about 1200 rpm.

I have a 16v Euro S, which is converted to Megasquirt. However, I expect this to be more an engine related issue than an ECU related issue. E.g. could the cold bypass system be faulty? How? Or anything else?

993turbo

Vacuum Leak?

Lizard928

This is likely a tuning issue.

You need to ensure that your AFRs are balanced as close as possible in that area, also look at the ign curve there.

Bart-Jan

Thanks Colin. The AFR is constant in that area, but quite lean: 15.5:1 Could that be the reason?
The ign curve could be a good source for the issue; didn't think of that... at 800rpm the advance is 10 degrees; at 1300 rpm it's 15.4 degrees.
Have you got an ignition map for a 16v that you could share?

Lizard928

Bart-Jan,

Bring the AFR for idle up to 14-13:1 for tuning purposes.

Email me your MSQ file (tunerstudio or megatune?), and I will edit it and fire it back to you for the ign curve.