[Cyruz (Dotdash)]

Erratic idling is a common problem with 306's (and all Pugs with XU engines). I've just had the problem with my 1997 2.0 16v XSi. I had poor idling, sometimes even stopping altogether at traffic lights etc, and also poor response and a drop in power. First thing I did was change the oil. I suspected that the garage that serviced my car last put rubbish oil in, or oil of the the wrong grade (XU engines - i.e. 1.8 and 2.0 - need 15W 40 oil, not sure about 1.4 or 1.6, prob the same). The wrong grade of oil means that the hydraulic tappets, which rely on oil pressure to maintain a tight gap between camshaft lobes and valves (16v engines only) won't work properly, which mean the valves won't open as much as they should and therefore the engine lacks power and response. Before I drained the old oil I used some Wynn's Engine Flush (fiver from Halfords) to remove crap left behind from rubbish oil. Replace the filter too. The idling problem itself was solved by removing the throttle body and giving it a clean up with solvent - i used brake degreaser, which did the job. Basically, the crankcase is vented into the throttle body so that unburnt hydrocarbons that get past the pistons get a second chance at being burnt. The crap oil led to the internal workings of the throttle body getting cacked up with a sticky varnish - this was stopping the idle control valve from operating correctly. Stuck closed and your engine stops, stuck open it idles at 1500 to 2000 rpm. This isn't as big a job as it sounds - undo some electrical connections, couple of hoses (there may be a hose from top of engine cover to throttle body, remove and make sure there's no cack inside) and three bolts. Just take care not to damage gaskets.

If that little lot doesn't return your Pug to it's former glory then you're probably looking at sensor failure, dirty electrical connectors or a dodgy ECU (the latter is very unlikely).

Good luck!

Ripped this from the preloved.com forum, there seems to be quite a few problems with irratic idling...