What has happened, i've a my01 which was running fine.So i decided to change the air filter for a K & N Panel filter to see what improvements this would make. Now car feels hesitant between 5-7000 rpm in fact on a private road it would not do more than 125 in top ,may be imagining it but petrol consumption seems to have suffered also. I did disconnect the battery for a few hours though,could this have affected the running .After reconnection ? car has been running on optimax prior and have had no problems until now.Funny thing is car seems quicker up to about 5000 rpms. should i stick with it or change back to original filter.,cant believe a filter could makes so much difference !

Any help would be appreciated . Sandman

thought it was just me that is having trouble with my01.I've changed my filter but for an ITG item.you sure its the filter,i've got the same top speed problem but its been there since before i changed the filter? U not got any other running probs e.g missing,hessitating?

CCPATON
No not really , car would normally run v smooth up to 140 + . I have noticed a hesitancy occasionally though usually from low speeds ie 30-40 when flooring accelerator pedal , the car seems fractionally slow to respond and also when backing off the power and then rapidly applying it again .But in general its ok does this help ? To be honest i've driven smoother cars.

Is it possible that you have both picked up a bad earth in the process of disconnecting and reconnecting the battery?
Check the connections for a good contact.
MG

Thanks Michael, I will check, I also had MAF connections off also, its worrying me , but must be related to what i've done, how long would battery be off to reset ecu and how long would a reset take ? does the ecu need to 'learn' the engine again.

May have solved it, put original element back in , lacks low down in comparison to K & N unit but improved top end straight up to rev limiter, this didnt happen or cut in with K & N maybe it was flowing too much air and was making engine run lean or something like that. Strange that it should make so much difference.very puzzled Sandman !!!!!

Sandman,

I have had the same issue with a filter some time ago.

It was like the AFS/ECU was flumoxxed by seeing so much air going past, and would turn off the fun at high rpm. Like yourself, going back to std fixed it.

I should add that installing an earthing kit enabled me to use A/M filters though...(note: on a Legacy)

Cheers :)

I think Dr Evil (alex) had probs on his MY01 when they RR'd it with a different filter - the power reading was spiking up and down all over the place........very irregular.
Perhaps the new cars don't like to breathe better???? :confused:

If a filter isn't fitted correctly, air will bypass the filter body. This air is travelling very fast and is very turbulent. It will confuse the MAF and the ECU will overfuel.

Peter ,thanks I had a feeling that it wasnt seating properly .The K & N part no was NM 33-2031-2 .It seemed to lack the rigidity of the OE filter.