Would a leaking intercooler cause rough idle?

[alphatarget1]

I had a shop look at my oil leak and he said the turbo oil outlet and the intercooler are leaking. He also said the rough idle (not horrible, but not silky smooth either) is caused by the leak in the intercooler. Is this possible? 2005 Subaru legacy gt

 

[EightySix Four]

I know nothing about the Legacy GT layout but if the MAF is before the leak then the ECU will expect more air than it is getting. Depending on the difference between expected airflow and actual airflow there could be significant excess fuel causing a poor idle and making it run rich in other driving conditions. This condition would be exacerbated under throttle though (depending on the size of the leak boost would cause a greater loss of air) and should cause you to run noticeably rich.

 

[jlee]

IIRC with Subarus a boost leak can cause such issues- metered air is escaping before combustion. MAP sensor based engines are more tolerant of leaks since they're measuring manifold pressure and not air volume.

 

[JCH13]

Leaks like that could possibly cause a rough idle, assuming they're downstream of the AFM/MAF in the intake, like JLee says.

 

[iamwiz82]

For sure. If you want to confirm the diagnosis take a propane torch and turn on the gas without lighting it. wave it around the intercooler, once it's near the leak it will siphon some of the gas in and you will hear the idle change a bit.