Gentlemen I need help please !!!

So here what I got. Cold start engine starts to rev up and down engine with pumping airflow from exhaust. Car shakes during this process left to right. This happens only when you in idle or stopped at the light. As soon as you press on throttle everything goes away. Also worth mentioning there is a little whistling noise coming from around bottom right area of engine. I used to have vacuum knocking sound described in one of the topics on this forum but now it went away.

Can this issue be caused by vacuum pump ??? Anyone got anything similar in the past ??

Things I have checked so far:
- PCV valve
- vacuum leaks
- manifold

Any feed recommendations would be much appreciated !!

 

just an update for everyone.

today was around -7 in GTA and car had no issue with shaking but I did hear vacuum valve knocking once again. I am thinking for some reason what ever the problem could be it gets out when its very cold - below -15 or so. We are getting few more days of cold here next week so I shell test my theory

 

Oleg, I don't have a specific part in mind, but I expect that you are getting inconsistent fuel, or possibly inconsistent air flow into the engine. I'd guess the engine control feedback loops are causing the up/down. The pumping exhaust would just be a product of the engine rpm fluctuation. Check out things like the MAF sensor, knock sensor, O2 sensor(s), fuel filter, etc.

good luck!

 

thank you for idea Paul902

This morning as predicted nothing happened since it was warm again. Tomorrow we expecting -16C so we shell see what happens then