The car in question is an 03 mk2 Megane 1.4, about 95 thou on clock, 5 door manual.
Right problem is two fold but i think related.
I get a noticeable surge and dip in power when im cruising with very light throttle. If I accelerate or put the engine under load everything is fine. She still pulls as good as the day i bought her. The best way to describe the feeling is like on a very windy day and you get caught by a head on gust of wind. It slows you down for a second then you speed back up slightly and continue as normal. However it does this repeatedly until either the engine load changes, road incline etc or i accelerate. There's no EML lights or other warnings lights when it does it.
The other problem is extremely rough idle. Shaking the car rough. When you look at the engine it looks like it very sharply jerks towards the front or rear of the car every other second and this jerking is what can be felt inside it.
These symptoms happen regardless of temperature or running time.
Ive hooked her up-to my computer using EasyobdII to check for fault codes and nothing, nada. EasyobdII has a data logging feature which id be glad to run and post if it would be off any help.
Ive replaced plugs and coils to no avail, ive serviced her, always regular anyway, to no avail.
I feel more then confident carrying work out. Ive done all the work to all my cars, welded sills(found it scary as hell
), done a head gasket once rebuilt brakes suspension(found great fun) etc. However i really struggle diagnosing issue's when its not a simple knocking.I love working on my cars and always want to better myself, so id greatly appreciate any help on the problem but if you guys n gals don't mind spending the time to type it, in a nut shell how would you go about diagnosing this issue if it was your car? What process do you follow?
Thanks all stephen