Abnormal engine rotation during warm up
I have recently bought an 156 2.0 TS 1999 and this is my first post in alfaowner forum. Glad to be here!
This is the problem I have: When engine is cold, after startup it goes to about 1200 rpms, maybe 1 minute later, little by little revs reduce to 900 (guess this is normal operation). Few minutes later, temperature reaches 50 deg C and engine rotation drops to around 500 rpms, engine almost stalls, then rotation increases to around 800 and then drops, and it keeps doing this irregular operation for about 2 minutes and the problem just disapears when temperature increases just above 50 deg C. During the abnormal operation, engine does not respond to throttle.
Few days ago I made an experiment, after an engine cold start, I contolled throttle to maintain at around 1400 rpms. When temperature reached 50 deg C, revs dropped to 1100 rpms stayed there for 1-2 seconds and then returned to 1400, and kept doing that until temperature got hotter than 50 deg C.
Any ideas or suggestions? I thought of making an ECU/throttle reset.
Thanks in advance,