LS swapped S10 lean maxing out o2 sensor
LS swapped S10 lean maxing out o2 sensor Hi guys have a problem with running extremely lean. I got the 6.0 put back in the s10 due to pulling the heads and putting new lifters in. I was logging the idle and it started climbing in the trims to a point where it maxed out the drivers side and passenger side was not far behind. I thought the intake gaskets were leaking since I reused them so put a new set on and the same.I tried unhooking both o2 sensors to see what it would do Monitoring it with an installed stand alone wideband and it was reading 19 afr. It was actually running not bad. Any idea what could cause this? It was fine before. I did find on the shorty headers it was leaking at the header gasket and also down on the 3 bolt collector pretty bad. The O2 sensors are down stream of the leaks as well as the wideband sensor. Could the exhaust leaks of messed with the o2s making it go positive on the trims? If so I'm guessing it would mess with the wideband as well since they are both down about 8 inches from the leaks.Could it be not really lean and just being fooled to think it is from the leaks? Thats the only thing I can come up with.
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So it's lean only at idle? What about when you hold the rpm at 1,000 or 2,000 or 3,000 rpm? Does it stay lean or get better?
Typically, a vacuum leak would be lean at idle, but would improve as you rev the engine.
Typically, a vacuum leak would be lean at idle, but would improve as you rev the engine.
it stays lean even off idle. I really don't think it has a vacuum leak. I just wonder if the leaking header is letting oxygen go past the o2 sensor tricking the pcm into thinking it's lean and adding a ton of fuel. That could explain why the trims are ramping into the positives so much
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it stays lean even off idle. I really don't think it has a vacuum leak. I just wonder if the leaking header is letting oxygen go past the o2 sensor tricking the pcm into thinking it's lean and adding a ton of fuel. That could explain why the trims are ramping into the positives so much
You can check the O2 sensors by doing a quick squirt with carb cleaner or temporarily unhooking a vacuum hose. In both cases you should see a response on the O2 sensor waveforms. I guess you are running the AFM wideband? Can you hookup something that can graph O2 sensor data? Or I guess that shows up on your guage?
Last edited by strutaeng; Dec 4, 2022 at 12:24 AM.
I have not checked fuel pressure but I never had this problem till I changed the cam and lifters. It’s mostly the drivers bank that is trimming to max positive. Passenger side is climbing some but not like the drivers side. The drivers side has the worst exhaust leak too
No I used a texas speed stage 2 low lift truck cam.I have the same cam in my silverado so I just flashed the same tune into the s10 since it's exactly the same setup. Good starting point. Then I even tried the current tune the s10 already had with the exact same results. I can't imagine the cam would have anything to do with this because Ive done dozens of cam swaps and yes they all needed tuned but nothing to the extreme of maxing out the o2s. Do exhaust leaks have a pretty big effect on the o2 sensors if the leaks are up stream from the sensors?
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Verdad Gallardo that does make sense. When I unplugged the o2s to stop it from adding fuel it actually idled pretty well. The wideband was reading about 19 afr but I would guess the wideband would also be effected. So it probably wasn't as lean as it was reading? I found the shorty header had several pin holes near the collector flange plus it was leaking at the collector and on top of that about 4 inches below the collector where the o2 screws in it had two very large cracks on each side of the sensor. Plus it had a small leak where the header bolts to the head. Every leak was above the sensor. It ran fine before I took it apart. It probably had the small pin holes but the large cracks beside the sensor was probably caused by me when I was wrenching like crazy trying to get the sensor out. It had no real leaks till after. I could clearly hear it plus could see steam shooting out of the collector.