as the title says .. what can cause a lumpy idle?

here's my lil story ..

i have bought my Evo7 a few months back from a guy i know. the car previously had a 2.2L setup with a T67 plus supporting mods modified tuned by JUN using F-con with no maf. the JUN engine blew and they had to put back a stock engine.

so when i bought the car it had the stock engine with a 50 trim turbo. all the other supporting mods for the 2.2L setup was still there (1000cc injectors, f-con ...etc). but the idle is funny. even though it has the stock engine, my idle is like 1100-1200 but not smooth. it goes up and down like it has cams on it and also it sounded like it!

so yesterday i removed the valve cover to check if it had after market cams after another friend told me that it possible that it has after market cams. so i found a code written on the cams (1G 13). and since im just a rookie in 4G63 i dunno if they are stock or that code means something.

could it be the F-con thats causing the lumpy idle? could it be cams? im confused! i cant even switch on the AC while idling without the car dying!

 

the large injectors can cause a lumpy idle.

i dunno bout the cams, someone will have to fill you in on that...

 

A lumpy idle can be caused by a myriad of things, a vaccum leak, bad tuning, cams, a bad throttle position sensor, incorrectly installed parts and the list goes on. The FCON would only cause idle problems if it was not installed right ,faulty or not tuned right. If you do have cams on the car the idle can be made better by a good tuner.