Changed catback now AFR crazy

JPsi02 · Post by **JPsi02** » Thu Mar 18, 2010 10:44 am

Uploaded current map and datalog to show crappy AFR.

Built B16A NA right now but low CR pistons in EG chassis
P28 S300
AEM UEGO
ID 1000cc
walbro 255hp
E85 fuel

So yet another crazy stupid problem. I had an eBay N1 style exhaust on my car and everything was fine but i was getting sick of it. So i purchased and install the Apexi World Sport 2 on my car. I didnt touch my testpipe (where the wideband is mounted). Well i go to testdrive the car and as soon as i get to around vtec point my AFR kicks to full lean 17.77 (AEM UEGO) but still felt fine. Well about my 3rd test pull when it shows full lean the car is like chugging and feels like major crap when vtec hits. Ive tried adding up to 30% fuel on the top end but it still shows full lean and feels even worse. MY AFR with the old exhaust was a steady 13.2 AFR throughout which is where i wanted it.

Things im thinking are this... Im running E85 and its been about 2K and i havent changed my fuel filter yet so maybe its getting clogged not allowing my pump to push the fuel needed from all the gas crap left over in the 18 year old tank and lines and it just happened to happen after i put the exhaust on.

Spark plugs are getting on the old side but that wouldnt cause leaned out AFR imo.

My wideband sensor is only 3K old but mounted straight up and down insted of an angle which was stupid but welded the o2 bung in without thinking with the testpipe out of the car so maybe condensation or something ruined the sensor from being at a stupid angle. The wideband gauge is grounded to a good ground and it read fine before i changed the exhaust.

Im at a real loss here why it feels like crap and the wideband is showing full lean all the time when i reach vtec :(.

Post by **Spunkster** » Thu Mar 18, 2010 12:12 pm

Perhaps your old exhaust was very restrictive and the new exhaust is much more free flowing. Try adding more fuel and see if you get any change at all. If you are not, it may be your wideband, or it may be a fueling issue.

JPsi02 · Post by **JPsi02** » Thu Mar 18, 2010 5:45 pm

I replaced the fuel filter today and it resulted in no change. So i took my wideband out and did the gas rag trick to see if it was bad and sure enough my sensor was bad :( so i ordered a new one. No wonder my readings were all over the board. The exhaust prolly changed the top end AFR but my wideband is not reading right at all so i cant even begin to tune it.