My car has been having a rough idle for about 2 months now, i'v replaced plugs,wires,coilpacks,mas,and did a compression test etc. The car drove fine and it boost fine. Until yesterday after i put on a new oil return hose from turbo i took it for a drive and when i came to idle it started to run really rough and the boost gauge read 10 to 15hg of vacuum when it usually reads 20-25hg. And when boosting the car car will hesitate alittle. Is this for sure a boost leak/vacuum leak. Also do i check everything from the intercooler piping to all the vac lines connected to intake manafold. Thanks

 

I would check out your BOV. The tock BOV sucks and leaks offen. So if i was you i would change it to like a greddy type RS with a recirculate kit or something.

Im willing to bet its the BOV.

 

thanks for the help but i'v already got a greddy type rs already installed although that could also have aleak. Im going to make a boost leak tester today and hopefully can find the leak. The lose of vacuum my boost gauge indicates does point to a vac leak right. thanks

 

oh yea it is also resirculating.

 

Legend. You and i will get on

It can be either i think... it can be a boost leak or a vac leak.

 

I just took it for a drive around the block to see how it acted and im still losing vac and it runs like bad at idle but my boost comes on like it always has and im not loosing any boost pressure. Very confused? Going to do a boost/vac leak test tommorrow. Any more sugg would be great. Thanks

 

Vac leak

 

thanks for your replies i'v been dealing with this for a couple of months now and i just want to get it fixed but if i can't find the prob im going to have to return the car back to na and take it to mits because they said they didn't want to deal with it if it had a turbo kit on it.

 

are you a turbo 420a?

 

no a 2002 lancer oz with a Road race motorsports stage 1 intercooled turbo