Thread: 940 WOT o2 is lean?

Bad fuel pressure, a ****ty fuel filter, or crappy/dirty injectors will cause your IPW's to go up (this is assuming you tune, you would have to "add" fuel to get your car to not die)

you really shouldnt max out your injectors on a 3.4, and you are. 20ms at 6krpm is MAXED.

Your ipws are definately on the high side for your mods and you dont want to see over 21, 20 as mentioned above is definately more towards the safe side. Something not mentioned about your high ipws could be that you are just flat out pooring too much fuel to the engine and as Lee mentioned earlier in this thread making a car run overly rich to cover up KR is not the ideal answer and wont make the best power. Once you get a wideband it will tell the story and until then I probably wouldnt mess with it more until you know exactly what your afr is. My L67 cutlass 02s are around 885 when the wideband is in the 11.8 range and i find many cars show low 900s, but I have also tuned cars in the 12.1 range intercooled and its showing 840s. The worst oddball I found was a car with S1X cam and headers and it was 965 02s showing 11.6 afr! I also find that on repeated runs the 02 numbers are never consistant but the wideband will stay on the money. This alone can lead you astray as after you make adjustments the 02 numbers dont follow what you thought they should. You can also get KR from running too rich. Im not sure who did or did not follow my thread last fall on cgp about exhaust restrictions but when I was working on Lee's Impala last october I ran into 3-5 deg of KR at the stop of second no matter what pulley I had on the car. After scratching my head for a few days and getting agrevated that I could not find the reason in the tune or fueling to not cooperate I decided to pull out the front 02 sensor and install a pressure gauge. BAM right off the bat the problem was obvious! In second gear over 4K rpms IIRC my 10 psi gauge was pegged! I thought well maybe the car was too rich in the past prior to my work and the cat was trashed so I removed it and it looked fine. Then I put the gauge in the rear 02 sensor hole and drove it again, same exact thing it pegged my 10 psi gauge. When I came back this time around and let the car sit I jacked about 10 minutes and jacked it up to remove my gauge fitting and wow was I shocked. He had just had the resonator replaced and it was apperently WAY too restrictive. 10 minutes after the car was shut off I got my infrared temp gun and the resonator was over 100 deg HOTTER than the cat was!!!! Bingo problem found. I took the res out and welded in a piece of 2.5" pipe in its place to rule it out and took it out and the pressure dropped way down and the KR was gone. Without testing backpressure in the exhaust I would have never found this and would have been a bit dissappointed in the performance and pulley sizes we were swayed to use, so try to keep in mind ANY possibly problems!

Added.... I forgot to mention that to prove the resonator was at fault I took the catback off the car and drove it again with the gauge on it to make sure the backpressure problem was gone and that it WAS in fact causing the KR problem. Unbolting the catback is easy and you can often just wire up the exhaust to keep it from hanging low and not have to remove it completely.