Hi All,
I wanted to see if anyone else has seen something like this. Basically, my car will go lean as it goes through ~2500 to ~3000 RPM. This happens regardless of load, gear, etc. It also doesn't seem to be related to the MAF or MTF because it does it with a different MAF and CAI.
If I'm accelerating onto the highway it starts to go lean around 2500RPM, peaks at 15.5 - 16AFR and then drops back to normal by around 3,000RPM. It does this through each gear. I can also make it happen when driving normally in fourth gear. If I bring the car up to 0" of vacuum or low boost (2 - 3 psi) at 2500RPM it will start going lean, peak and then go back to normal by 3,000RPM. This is at steady throttle, too. Outside this RPM range it seems to be OK. It doesn't appear to be a sensor issue because if I accelerate I can feel the car slightly pull back as it goes through 2500-3000 and then take off again.
I was thinking it might be a transient fuel issue, but it happens after the transient. So, I can make the tip-in rich, but it will still happen after that. I've had a well-known tuner work with me and he's as stumped as I am. MAF counts, throttle position, etc are all steady through the range, but the AFR drifts lean, peaks and goes back to normal.
Logs are below and you can see it happen beginning at 144 seconds and end at 174 seconds. This is accelerating onto the highway going through 2 - 4 gears. It does it at the same point in each gear.
Log File
Thanks!!
Riley
I wanted to see if anyone else has seen something like this. Basically, my car will go lean as it goes through ~2500 to ~3000 RPM. This happens regardless of load, gear, etc. It also doesn't seem to be related to the MAF or MTF because it does it with a different MAF and CAI.
If I'm accelerating onto the highway it starts to go lean around 2500RPM, peaks at 15.5 - 16AFR and then drops back to normal by around 3,000RPM. It does this through each gear. I can also make it happen when driving normally in fourth gear. If I bring the car up to 0" of vacuum or low boost (2 - 3 psi) at 2500RPM it will start going lean, peak and then go back to normal by 3,000RPM. This is at steady throttle, too. Outside this RPM range it seems to be OK. It doesn't appear to be a sensor issue because if I accelerate I can feel the car slightly pull back as it goes through 2500-3000 and then take off again.
I was thinking it might be a transient fuel issue, but it happens after the transient. So, I can make the tip-in rich, but it will still happen after that. I've had a well-known tuner work with me and he's as stumped as I am. MAF counts, throttle position, etc are all steady through the range, but the AFR drifts lean, peaks and goes back to normal.
Logs are below and you can see it happen beginning at 144 seconds and end at 174 seconds. This is accelerating onto the highway going through 2 - 4 gears. It does it at the same point in each gear.
Log File
Thanks!!
Riley
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