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running lean

This is a discussion on running lean within the Computer & Tuning forums, part of the LSx Technical Help Section category; Part throttle and wot. My long trims fuel trims are anywhere from +8-16+. I checked the plugs and there confirming ...

  1. #1
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    2002, CAMARO Z28

    running lean

    Part throttle and wot. My long trims fuel trims are anywhere from +8-16+. I checked the plugs and there confirming a lean condition. Also my exhaust starts sounds different after driving for maybe 20 minutes then the pinging starts. So far I have checked fuel pressure, about 60 all rpm's. I have replaced the fuel filter, cleaned the maf and tried another maf. Tested the mass air sensor pigtai for voltage with in spec, tested front 02 sensors. Also my short trims at times go up to +22. I am thinking exhaust leak because of the sound of the exhaust, chug chug like sound. Also my mpg is in the toilet and getting worse each tank full.

  2. #2
    Junior Member Intimidator02SS's Avatar
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    2002 Camaro SS

    is your check engine light on?
    possibly skewed map sensor readings, or tps sensor issue. I wouldn't think vacuum leak, because your issue is at part throttle and wot. (I assume it's not an issue at idle). I don't know about the "chug chug" sound, but if you have an exhaust leak it would have to be on both sides to affect both o2 sensor readings.
    what mods do you have, what tuning has been done?

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    No check light or codes coming up. I check for that daily. The tps sensor and wiring pigtail is new. I replaced those a couple months ago because I have a closed loop idle problem. The idle drops for a few secs after I come to a stop. I had a friend who has autotap and my iac counts and readings were 0 the whole time. This issue has been going on the past two yrs though. At idle my fuel trims at times will read a even negative number and other times read positive. Also I had a code po420 for the driveside cat, but I think that was because I had a bad air pump check valve and rotted hose. I replaced the part and hose a couple weeks ago and that about when this lean condition got worse. The car was already running lean before but just more lean now. I have just a predator tuner to read live data. I am on the STOCK TUNE though. What kind of readings should I be looking for regarding the map sensor?
    2002 Camaro z28, m6, direct flow lid, maft, powerstick muffler with stainless z28 tips, lakewood lca, predator, vacuum gauge inside car, ngk tr55, msd wires
    stock dyno 310 rwhp, 329 trq

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    The code po420 I cleared a month ago and hasn't came back. I checked the back pressure on that side and there was none so no plugged cat and no more smell after replacing the check valve and hose.

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    Well it turned out to be the mass air sensor. The third stock maf to go bad on this car. I have a slp maf I bought yrs ago and it works fine.

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