when the car is at idle, the tach (RPM) needle goes down, then the engine shakes like it's trying to push gas into the engine to keep it running and the needle goes back up to 1500 to 2000rpm.
what could be wrong with it? is it the question of replacing the spark plugs? fuel injector cleaner?
p.s. the car is a stock Lancer O.Z
thanks in advance

 

could be the throttlebody, spark plugs, coils, 80 octane gas hehe but in what kinda motion does it do it like up down up down or like slowly... try to describe it as best as possible..

 

mine does the same thing, but i also got an engiine code saying i am running lean, it sounds like my car is having a hard time breathing

 

the needle just goes down slowly, almost goes below 500rpm, and then the engine revs and the rpm goes to about 2k, and keeps repeating the cycle. it does it at idle usually after having driven it 50km or more.
i also keep getting the yellow check engine light, it comes on, but after having driven it for half an hour with the light on, it'd disappear.

 

take it to the dealer and have it checked.

 

Try to reset your ecu, if that doesn't work, definetly take it to the dealer.

Just in case you don't know how to reset the ecu:
1. Disconnect the neg terminal of your battery for 10-15 minutes
2. Plug it back on, start the engine and let it idle for another 15 minutes
3. Take if for a spin
4. Enjoy or bring it to your dealer

 

well i got mine fixed, it turned out to be my mass air flow sensor, the restrictor plate somehow came off, so right now i just glued it back on, it seemed to have solve my problem of my car running to lean, and my rough idle. im getting a new mass sensor tho the glue is just temporary

 

Hey hold on to your old one for me....I may need it....I have to take the restrictor plate off anyway for this turbo I have...

 

yea sure np, why might u need it tho?

 

I dunno...in case mines is screwed after toying with it...