mbarb55

Hey guys, I have a 1999 firebird ws6 m6 with a rough idle that seems to get slightly worse after it warms up. It feels like a misfire but I'm unsure. It feels fine driving, iv also noticed that my mpg seems to have gotten worse. (I don't have any exact numbers, sorry)

Things I have done/replaced:.

Cleaned maf x2
cleaned idle air control valve x2
Replaced spark plugs
New msd wires

My mods:

K&N cold air intake
Borla cat back
(I suspect and one point this car ran Nos. I found a braided brake line going from the firewall to the hatch)

I've also questioned if potentially this car has a crappy tune but can't prove it. I've attached logs from my car driving and idling. I'm hoping that someone can read the logs and let me know if something isnt right. I have a suspicion it may be o2 sensors but I'd like to be sure if that is possible .

(Apologies if this is in the wrong place)

Thanks in advanced everyone.

mbarb55

Is anyone able to help?

Fuhnortoner

Vacuum leak.

mbarb55

I agree it could be a vacuum leak however I checked everything I can see and haven't found anything. If the logs don't show anything useful I will have to get the pcv system checked.

Fuhnortoner

The logs show an idle MAP of ~5psi, which correct me if im wrong is low for a stock cam.

mbarb55

If that is indeed low, is that indicative of a vacuum leak or something else?

mbarb55

Any other assistance is appreciated

Fuhnortoner

If I were you, I'd make a boost leak pressure tester similar to the one below. I made mine out of a plastic PVC cap and a valve stem.