I have a completely standard Hawkeye 07 WRX with 35k. For over a year now when the car is warmed up and stood still there is a slight judder on the idle every 2-3 secs. It is not big enough to register on the rev counter which holds steady at 800 rpm and doesnt change if the clutch is depressed. It doesnt seem to be causing a problem just more of an annoyance but determined to get it sorted out. I had it plugged in at a non-subaru garage a while back and they said it was running a little lean. I know that strictly it doesnt need to as it is not the STi but it has always been filled with Super Unleaded (Total Excellium 97 RON 90% of the time as they are my local garages and Shell V-power the rest) so I am possibly thinking of the following:

1) Car is running slightly lean so constantly trying to correct the fuel/air ratio itself?
2) Is timing trying to constantly adjust itself due to the 97 Ron fuel?
3) Slightly loose engine mounts?

Any other ideas? Am I right in thinking that the fuel / air ratio can only be ammended by accessing the ECU i.e. by a dealer or a mapper?

Thanks in advance

 

Get it into a reputable mapper, bob rawle, JGM, andy forrest, they will tell you if there is anything wrong

Don't let this worry you, but the engine builder that previously built mine used the wrong sized head gaskets, and the vehicle had the most annoying wobble on idle, you could even feel it through the gearbox, i rebuilt the engine due to it smoking on overun, then there was no more wobble! Obviously if your engine has never been apart dont worry!

 

ive had three scoobs to date and none of them have idled really smoothly.sometimes there fine but often they have a slight miss.if its only slight like you say and the car drives fine dont worry about it.if you think its bad you should try a renault.had a 182 clio and a r26 megane which both idled terribly.as long as your revs arent rising and falling im sure it will be fine