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Discussion Starter · #1 · (Edited)
ok.. heres the problem... 99 GTP, lots o mods... idle yields high negative LTFT #s, -10 to -17. WOT High RPM has 0 to -2 LTFT, but 02 comes up at .880-.890. Heres what is in the car...

8:1 diamond, .010 over
Light porting on heads
Polished combusiton chambers
Stage 1X cam
ZZP Stage 1 TB, no screen
CAI
SLP Headers, 3" exhaust, 2.5" after Y, Magnaflow mufflers.
L32 Rods
No balance shaft, balanced motor
Intense Stage 1 PCM
3.2" pulley
Autolite 104 (had 103s in, but its cold here now..)
180 Stat (again, need heat in winter!!!)
EGR Delete
other misc things that arent really relevant...

I tried a MAF from my buddies Stock 2000 GTP, same prob
Replaced 02 sensor
Tried different FP regulator
Took out walbro pump and put a brand new stocker in (wow, no more radio whine! thats what was causing it!)
Traced all connections from vital sensors back to ECU and checked for shorts/proper voltage (MAF, O2, TPS).

Everything I tried nets the same results. Why is the computer trying to lean out the mixture making it run .880-.890 on 02 sensor. The setup isnt the most radical in existence, so there must be some stupid answer. Follows is a HPtuners log (Its for my friends vette so i cant make changes.... yet....) on a run w/ 4 degrees of timing pulled out in hptuners scanner...

This run shows +1.6 LTFT, just after a fuel trim reset, but it ends up drifting downwards into the negatives. Mind you this was in 40 degree weather, check out the numbers for idle though...

Engine RPM (SAE) rpm Vehicle Speed (SAE) mph Ignition Timing Advance (SAE) ø Knock Retard ø Mass Air Flow (SAE) lb/min Manifold Absolute Pressure (SAE) kPa Intake Air Temp (SAE) øF O2 Voltage B1S1 mV INJ. Pulse Width Avg. Bank 1 msec Short Term Fuel Trim Bank 1 (SAE) % Long Term Fuel Trim Bank 1 (SAE) %
3964 77 8 0 25.97 166 55 868 19.2 0 0.8
4024 77 17 0 26.04 164 55 877 19.4 0 1.6
4191 77 17 0 27.36 166 55 877 19.5 0 1.6
4683 77 17 0 29.97 169 55 872 19.5 0 1.6
5161 79 17.5 0 33.92 168 55 872 20 0 1.6
5042 78 17 0 33.54 168 55 877 20.2 0 1.6
5081 80 17.5 0 33.74 164 55 877 20.1 0 1.6
5121 80 17.5 0 34.25 170 55 881 20.4 0 1.6
5141 80 17.5 0 34.05 169 55 877 20.1 0 1.6
5202 81 17.5 0 34.61 168 54 881 20.4 0 1.6
5181 81 17.5 0 34.72 168 54 881 20.4 0 1.6
5243 82 17.5 0 34.9 168 54 881 20.2 0 1.6
5264 83 17 0 34.94 168 54 890 20.2 0 1.6
5285 83 17 0 35.25 169 54 881 20.4 0 1.6
5306 84 17 0 35.25 168 54 881 20.1 0 1.6
5328 85 17 0 35.5 170 54 877 20.3 0 1.6
5371 85 17 0 35.98 171 54 881 20.5 0 1.6
5371 85 17 0 36.18 171 54 881 20.4 0 1.6
5416 86 17 0 35.85 168 54 877 20.1 0 1.6
5438 86 17 0 36.09 170 54 881 20.2 0 1.6
5483 88 17 0 36.19 168 54 881 20.2 0 1.6
5506 88 16.5 0 36.83 171 54 885 20.4 0 1.6
5529 88 16.5 0 36.67 171 54 885 20.2 0 1.6
5553 89 16.5 0 36.69 172 54 885 20.1 0 1.6
5576 89 16.5 0 37.13 174 54 885 20.4 0 1.6
5648 89 16.5 0 37.41 172 54 885 20.4 0 1.6
5624 90 16.5 0 37.3 172 54 885 20.1 0 1.6
5697 91 16 0 37.38 173 54 885 20.3 0 1.6
5672 91 16.5 0 37.92 173 52 890 20.2 0 1.6
5747 91 16 0 37.7 173 52 890 20.2 0 1.6
5722 92 16 0 37.96 174 52 890 20.3 0 1.6
5772 93 16 0 37.99 174 52 890 20.1 0 1.6
5823 93 16 0 37.99 174 52 890 20.2 0 1.6
5823 94 16 0 38.06 175 52 885 20.2 0 1.6
5823 94 16 0 38.21 177 52 890 20 0 1.6
5901 94 16 0 38.68 178 52 890 20.3 0 1.6
5928 95 15.5 0 38.62 178 52 890 20.1 0 1.6
5901 95 15.5 0 38.77 177 52 890 20.2 0 1.6
5928 96 15.5 0 38.82 177 52 885 20.1 0 1.6
5955 96 15.5 0 38.7 179 52 885 20 0 1.6
5955 97 15.5 0 38.67 178 52 885 20 0 1.6
6009 97 15.5 0 39.08 179 52 885 20 0 1.6
6009 98 14.5 1.1 39.26 179 52 885 20.2 0 1.6
6093 98 15 0.7 39.32 178 52 885 20.1 0 1.6
6093 98 15 0.4 39.37 180 52 881 20 0 1.6
6064 99 15.5 0.1 39.52 181 52 885 20.1 0 1.6
6093 99 15.5 0 39.84 182 52 894 20 0 1.6
6121 99 15.5 0 39.49 181 52 881 20 0 1.6
6207 99 15.5 0 39.97 181 52 881 20.1 0 1.6
6178 100 15.5 0 39.81 180 50 881 20 0 1.6
6207 101 15.5 0 39.98 182 50 877 19.9 0 1.6
6237 101 15.5 0 40.14 184 50 877 19.9 0 1.6
6237 101 15.5 0 40.59 182 50 881 20 0 1.6
6296 102 15.5 0.3 40.3 184 50 872 20 0 1.6
6296 102 15.5 0 40.6 182 50 877 19.9 0 1.6
6357 103 15.5 0 40.6 185 50 877 19.9 0 1.6


At Idle, 02 reading? All connections are fine... whats wrong????
852 0 20.5 0 1.01 42 102 30 2.7 -7.8 -8.6
884 0 20.5 0 1.02 43 100 35 2.6 -7.8 -8.6
865 0 21 0 1.01 43 100 130 2.6 -7.8 -8.6
865 0 20.5 0 1.01 43 100 35 2.6 -7.8 -8.6
878 0 21 0 0.99 42 102 35 2.5 -7.8 -9.4
903 0 21 0 1.01 43 102 65 2.5 -7.8 -9.4
821 0 21 0 1 44 102 43 2.7 -7.8 -9.4
903 0 21 0 1.01 43 100 39 2.5 -7.8 -9.4
923 0 21 0 1 42 102 35 2.5 -5.5 -9.4
865 0 21 0 1 43 100 48 2.6 -5.5 -9.4
873 0 21 0 1.02 43 100 39 2.6 -7.8 -9.4
895 0 21 0 1 43 102 35 2.5 -7.8 -10.2
870 0 21.5 0 1 43 102 43 2.6 -7.8 -10.2
872 0 21.5 0 1.02 44 102 48 2.6 -7.8 -10.2
862 0 21.5 0 1 43 102 39 2.6 -7.8 -10.2
818 0 21.5 0 1 44 102 39 2.7 -7.8 -10.2
864 0 21.5 0 1 44 102 35 2.6 -7.8 -10.2
869 0 21.5 0 1 44 102 69 2.6 -7.8 -10.2
860 0 21.5 0 1.01 43 100 39 2.6 -5.5 -10.2


TIA, Tim

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1998 GTP coupe. Stock and rust free. Totaled @ 87K miles
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Discussion Starter · #3 ·
I just ordered hptuners.. but my thoughts are that the stage 1 PCM was "Designed" around a similair setup to what I have in place, so I should be alot closer on than I am right now. I just dont want to tune around a problem, ya know? That and after popping the first motor after multiple head gaskets due to a torque wrench malfunction, Timmy = brokeass. And now its christmas.. time to talk to mom and dad! :D If anyone else has any pointers to what the problem might me, please speak out.. Last night i reran all the vacuum lines to MAP and FP regulator to make sure it wasnt leaking, and there was no change.

Tim
 

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Are you running stock injectors? Your getting close with those IPW numbers to maxing out. I was seeing similar numbers on stock injectors. Went to 42.5# injectors and an AFC 2.0, made all the difference in the world. IPW's of 22.0 are max. But, when you start to get within 85 -90% of that max number all bets are off at WOT. That 85 -90 % is not an exact equation, just a rule of thumb. But is worth remembering. Good luck!
 

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Discussion Starter · #5 ·
Well, at 6K, 20ms is maxed.. well, theoretically, assuming injectors are opening as long as computer is asking... But that doesnt tell me whats up below 6000 when injectors are at 19-20ms and running lean..

Tim
 

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o2 readings don't mean alot at idle. And there's no doubt your on the lean side at Idle. But, not all that lean. An AFC will easily correct the mild lean condition at idle. Within -5 to +5 is not considered to be a worry. One question, when you accelerate and let off the gas completly what do your fuel trims do?
 
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