95 trans am lt1 diagnosing poor running/ running lean

**steveo** · 10-22-2014

your BLMs are reading rich in general when running a maf, but the dyno shows you being very lean at wide open throttle? that screams 'something is wrong with this picture' to me.

if your o2s are working correctly, yes, but keep in mind BLMs are only good for the range that the cell operates in.... so if you're expecting trim data from cruising to be valid at wide open throttle and high rpm.. well..

i think you have quite a bit of information that needs to be analyzed properly at this point, and stop just trying a whole bunch of different stuff trying to patch it together.

i really do think you're trying to patch a mechanical or metering problem with tuning, which is a very wrong thing to do.

so lets make sure you're running on all 8, dont have exhaust or intake leaks, your fuel pressure is solid, and all your sensors are measuring correctly.

if all those things were OK, it would NOT be doing this.

**zoomo** · 10-22-2014

believe it or not ive checked all that stuff multiple times including today. the only possible failing sensor i could see is the maf, though i dont see enough fluctuations in the readings for the to be true.

Did some more testing before leaving for the day. no matter what i do the computer corrects itself to the air fuel that you saw in the pictures. i even made a pass with the brake booster vacuum line disconnected. the highest it is getting is about 15.4-1, though it does go much lower in open loop. why is the computer correcting to this mixture? here is a drive home running a tune with 5% less on the maf scale around the cruising rpm, seems to have really helped my blms, though even with the corrcl where it should make little to no adjustments it is still split bad at idle.

Please feel free to tell me what im missing.

Edit: also wondering about doing a speed density tune for testing.
Also noticed that the current tune im using is using a stock PE correction at wot table. The one you had sent me was raised quite a bit, i assume this is raising the amount of fuel added at wot in pe mode. i assume i should use your bin for this and it may help. ha

edit added a dyno run lol

**roughneck427** · 10-22-2014

heres my tune from my old car i couldnt fine my final tune which i ended up doing 390 rwhp and forgot the tq it was a CC503 ported heads 12:1cr through mac mid tubes

**zoomo** · 10-22-2014

Thank you roughneck. I did not upload your tune but it is great comparison information.
Back at work today hooked up an 08 Mercedes to the air fuel and it reads lean at high 15s and low 16s so I assume this AF is out of calibration somehow. According to my obd2 scanned the mercedes is running perfect 14.7-1

**zoomo** · 10-25-2014

Well i think its getting close, still lacking a reliable wideband 02 reading though. after some more research and diagnosing it seems the filter is clogged and one of the pumps needs rebuilt on the dynojet wideband, which explains the lean condition, due to the lack of vacuum. I lowered the maf table by 10% in some areas and changed some timing and stuff. it seems to be running rich at idle though, i havent messed with it any. im starting to feel pretty good about it. thanks for all the help guys i really appreciate it!

**zoomo** · 11-08-2014

Well I finally got some time and new filters for the air fuel set up on the dyno. Just in case anyone ever comes across the same problem. The lean mixture was caused by the filter being slightly clogged on the intake of the dynojet air fuel assembly. I know this is somewhat off topic diagnostic for you guys but hopefully it can help someone some day.I can't thank you guys enough for all the time you spent trying to help.

So in summary if you're using a standalone wideband air fuel set up and reading abnormally lean, check out the vacuum it is pulling should be high like at least 15. And check the in line filter. Ha

**steveo** · 11-08-2014

usually i wouldn't bother even checking that, since dynos run many cars in a day, and if the wideband was screwed surely someone would have noticed by now, since every single car would be reading incurably lean. must be a pretty slow dyno if it took that long to realize.....