I had stillen's HFC's in stalled and about a month later my SES light came on had it looked at and it was determined that the gaskets were leaking. So I replaced the gaskets and it stopped the leaks but they started leaking again. Has any one had the same problem? and how did you fix it? Cobb AP said the problem is with cat 1 and 2 code Po420.

 

With anything exhaust related you should go check the the bolts at 500 miles after install. I have always done 500 and 1000 on all my cars. Expansion and contraction will cause the bolts to loosen up. After that you should have no problems.

 

You need a set of gaskets in there. The Stillen flange makes use of the OEM crush ring but the tolerances aren't quite close enough to allow the crush ring to seat properly.

Your options:

1. Smear a crap load of RTV sealant on there.
2. Get a set of our custom made gaskets on there.

But remember with either method (new OEM, spreading goop, or a gasket) it's essentially a R&R.

Similar to the one pictured, but for the 3 bolt collector flange obviously.

 

are you sure its the leak? cause i have the same issue... I spoke with Kyle@stillen and he said they are working on something to fix this issue.

btw p0420 and p430 means too much air going in to the sensor... I dont think its the leak.

was the leak from the header and hfc or hfc and mid-pipe?

 

Another thing to note.

Stillen uses the same cat that we do. The cats don't scrub the exhaust gas quite as well as the restrictive and OEM cats do. So CEL free operatoin isn't absolutley guaranteed.

The the OP, try using the stainless steel wool trick. Pickup a set of non-foulers (just search for it if you don't know what it is) and stuff them with stainless steel wool.

 

Sent a pm to Kyle@stillen I hope he can do something about this. I was hoping that the Cobb AP was going to fix this problem. But my SES light was on before I had my CAI and my HKS exhaust installed. Just with the HFC's

 

i spoke with Lou about Cobb AP and i think he said it wont fix that issue because AP doesnt control AF.. because of the liability

 

I'll look in to it thank's. My car run's like sh-t with the SES light on

 

btw do you still have that raspy noise from HFC with your full exhaust system?

 

I am not saying your wrong because I totally agree with you. I spoke to Kyle@Stillen and he said "from the factory the cars come with steel gaskets which are virtually indestructible." When I was installing mine from Technosquare they said new gaskets were needed. So I totally agree with you with gaskets.

 

Yes. If your talking about the back pressure air sound yes

 

Does those Cel fix on ebay work? the ones that extend your 02 sensors more outward screwing onto the bung?

 

If it is truly a P0420, P0430 (cat converter efficiency below threshold), it will have zero effect on engine performance.

The secondary O2 sensors only monitor the cat converter efficiency, they have no other purpose.

 

When I clear the SES light with my Cobb AP the car runs great but when it comes back on the car seems to louse some power off the line.

 

i had P2A00,P2A03(a/f ratio issue) b/c of the leakage befor the HFC since
i didnt have a gasket in there.

checked your web and couldnt find three point gasket for flange to the engine side.

If you have it PM me please.