Engine Trouble

[babzog]

Car is an '02 1.7EL.

Since Sept, I have been noticing that at lower speeds (1-3 gear), the car will tend to "surge" or "bunny-hop". This is especially noticable in stop 'n' go traffic, coming up my laneway, driving through parking lots, etc.

I seem to notice it generally goes away when the air is really cold and crisp (although it did happen once when it was -16C) and re-emerges when it's warmer outside.

The rpms will fluctuate when this is happening. When the car is behaving, the rpm will stay steady at around 750. When it's acting up, the rpm will fluctuate from 700-ish to 1200-ish. The service mgr at the dealer saw that fluctuation, but couldn't reproduce it in the shop, hence they have no idea what it could be.

I've replaced the air filter with a K/N replacement for the factory spec paper filter thinking that perhaps airflow might have caused it, but I don't think that's the case. I don't know if there's a PCV valve on this car - I know I've never replaced one if there is. Not sure what else to check for or tweak.

Anyone have some thoughts on this?