jojo-effect

[Wouter1973]

Since I'm Dutch, I'm not sure how to describe this. When I cold start my Legacy 2.0 GL the tachometer goes jojo-ing between 600 tpm and about 1400 tpm. It's like the engine is revving without me pushing the gaspedal. As the engine gets warm this stops, and it runs 700 tpm steady. Is this bad? A leak in a vacuum hose maybe? It's kinda annoying...

[BAC5.2]

Normal. The engine has a warmup period on cold starts to bring parts up to operating temperature.

Though usually, it will rest around 2000RPM for a second, then drop to about 1500 or so, then settle down over the next 60 seconds or so.

[Wouter1973]

Yea, it does that sometimes, when it's less cold outside I guess. This morning seemed to be quite cold (about 7 degrees Celcius below zero) so it started revving between 1400 and 600...