Alpine951

I put a wideband and maf in my car a few years ago. It ran great from months up until a first time WOT run. since then, the wideband says afr is very lean all the time - idle, cruising and on boost. Been looking for intake leaks but have not found any. I have pressure tested the intake multiple time and had the intake smoke testedat a Porsche specialist. nothing. tested a bunch of things and even threw money at it replacing O2 sensor and other stuff. fuel pressure is good. just realized that the spark plugs appear to be fouled so will be putting in new plugs. I have a ebay paint can smoke tester that I hooked up to the exhaust pipe with an aircompressor. lots of smoke leaking between the crossover pipe and flange where the flange attaches to the header flange. There is gap in between the pipe and flange where it is leaking as shown in the picture. I don't see a gap like this anywhere else around the pipe or on the other crossover flange. I am guessing there must be some crack or some separation there inside the flange. You can also see that where the gap is, the side of the pipe looks very clean with no rust on it. There is also smoke leaking at the downpipe flange at the turbine side of the turbo. unfortunately it is near the bottom turbo stud that is closest to the engine so not an easily viewable location. But from lying under the car and looking up I can see the the leak is above the bottom stud and from looking down from the top the leak is below the top stud, so inbetween both studs. can't tell if it is leaking inbetween the flange and turbo mating surfaces or if there is a crack in the pipe right where it meets the flange. Guess I won't know unless I start removing stuff to try and get the crossover and downpipe off.

SO the crossover leak is before both the narrowband and wideband sensor and the downpipe leak is after the narrowband but before the wideband. Would either or both of these leaks cause lean readings on the wideband? would it create any lumpiness in idle?

v8killer

I recently had my car dynoed and this is how the AFR's turned out. Discovered a crack in the header. In the process of replacing with Stage1 SFR header that I had sitting on the shelf to see if it fixes the problem. Normally AFR's sit around 11.5.

ealoken

Did you forget the exhaust rings ?

Alpine951

Pretty sure the are in there. Had it apart a few years ago.