Datalogging Code 44 Left o2 Sensor Lean
Last month the car threw both codes- Left and Right o2 Sensors Lean. It was running very rich, plugs looked fouled. Checked fuel pressure, it was sub 35psi- checked the regulator. Had slight fuel smell in the diaphragm so I replaced it. Fuel pressure improved but not the main issue. I also cycled the fuel pump with the injectors out of the intake manifold and none were leaking. Changed the fuel filter, bingo. Changed the plugs went for a ride and all seemed well for about a half hour. Car started to bog coming to a stop, smelled rich again. Drove maybe another 15 minutes with no SES light until I was parked idling for a bit -Code 44 Left o2 Lean. I cleared the code, setup a datalog and drove a bit. Car was behaving the same but no SES light until I got back home sitting parked - Code 44 Left o2 Lean.
The only thing that looks to be pattern is at idle, the Left LT Fuel Trim is at max 160 while the right side looks good, around 130. The other data set I have doesn't show vehicle speed but driving under load (looking at the RPM's) it seems both sides are all over the place. I'd prefer not to just throw two new o2 sensors at it but nothing seems to pinpoint the issue unless I'm missing something. I noticed a slight exhaust leak at the collector but the o2 sensor is upstream from it. I also checked for burned or damaged wires and all looks good there. Any ideas? Record Data FRAME: 0 TM: 0.0 A.I.R. PUMP OFF AC CLUTCH OFF AC EVAP(°F) 20 AC PRESS(PSI) -13.12 AC PRESS(V) 0.02 AC REQUEST OFF BARO("HG) 29.86 BARO(V) 4.82 BATTERY(V) 13.6 LT FUEL TR CL 16 LT FUEL TRM L 160 LT FUEL TRM R 137 EVAP DUTY(%) 0 COOLANT(°F) 177 EGR DUTY(%) 0 EGR VLVPOS 1 ENGINE(RPM) 850 KS COUNTER 2500 FC1 RELAY ON FC2 RELAY OFF IAC POSITION 48 IDLE REQ(RPM) 875 INJ L PW(mV) 4 INJ R PW(mV) 0 KNOCK RET(°) 0 LOOP STATUS CLSD MAF(gr/S) 9 MAP("HG) 16.79 MAP(V) 2.53 IAT(°F) 122 O2S LEFT(mV) 471 O2S RIGHT(mV) 591 RUN TIME 24:38 SKIPSHFT ENA NO SPARK ADV 26 THROTTLE(%) 0 TPS SENSOR(V) 0.49 VEHSPEED(MPH) 0 ------------------------------ FRAME: 1 TM: 3.6 A.I.R. PUMP OFF AC CLUTCH OFF AC EVAP(°F) 20 AC PRESS(PSI) -13.12 AC PRESS(V) 0.02 AC REQUEST OFF BARO("HG) 29.86 BARO(V) 4.82 BATTERY(V) 13.6 LT FUEL TR CL 16 LT FUEL TRM L 160 LT FUEL TRM R 155 EVAP DUTY(%) 0 COOLANT(°F) 177 EGR DUTY(%) 0 EGR VLVPOS 1 ENGINE(RPM) 1375 KS COUNTER 2500 FC1 RELAY ON FC2 RELAY OFF IAC POSITION 70 IDLE REQ(RPM) 875 INJ L PW(mV) 13 INJ R PW(mV) 9 KNOCK RET(°) 0 LOOP STATUS CLSD MAF(gr/S) 12 MAP("HG) 8.18 MAP(V) 0.96 IAT(°F) 122 O2S LEFT(mV) 58 O2S RIGHT(mV) 44 RUN TIME 24:42 SKIPSHFT ENA NO SPARK ADV 31 THROTTLE(%) 7 TPS SENSOR(V) 0.90 VEHSPEED(MPH) 0 ------------------------------ FRAME: 2 TM: 7.2 A.I.R. PUMP OFF AC CLUTCH OFF AC EVAP(°F) 20 AC PRESS(PSI) -13.12 AC PRESS(V) 0.02 AC REQUEST OFF BARO("HG) 29.86 BARO(V) 4.82 BATTERY(V) 13.6 LT FUEL TR CL 16 LT FUEL TRM L 160 LT FUEL TRM R 132 EVAP DUTY(%) 0 COOLANT(°F) 177 EGR DUTY(%) 0 EGR VLVPOS 1 ENGINE(RPM) 1550 KS COUNTER 2500 FC1 RELAY ON FC2 RELAY OFF IAC POSITION 64 IDLE REQ(RPM) 875 INJ L PW(mV) 4 INJ R PW(mV) 0 KNOCK RET(°) 0 LOOP STATUS CLSD MAF(gr/S) 10 MAP("HG) 14.17 MAP(V) 2.04 IAT(°F) 122 O2S LEFT(mV) 231 O2S RIGHT(mV) 448 RUN TIME 24:46 SKIPSHFT ENA NO SPARK ADV 37 THROTTLE(%) 10 TPS SENSOR(V) 0.80 VEHSPEED(MPH) 0 ------------------------------ FRAME: 3 TM: 10.8 A.I.R. PUMP OFF AC CLUTCH OFF AC EVAP(°F) 20 AC PRESS(PSI) -13.12 AC PRESS(V) 0.02 AC REQUEST OFF BARO("HG) 29.86 BARO(V) 4.82 BATTERY(V) 13.6 LT FUEL TR CL 18 LT FUEL TRM L 160 LT FUEL TRM R 154 EVAP DUTY(%) 0 COOLANT(°F) 177 EGR DUTY(%) 0 EGR VLVPOS 1 ENGINE(RPM) 1975 KS COUNTER 2500 FC1 RELAY ON FC2 RELAY OFF IAC POSITION 60 IDLE REQ(RPM) 875 INJ L PW(mV) 0 INJ R PW(mV) 0 KNOCK RET(°) 0 LOOP STATUS CLSD MAF(gr/S) 10 MAP("HG) 12.21 MAP(V) 1.69 IAT(°F) 122 O2S LEFT(mV) 44 O2S RIGHT(mV) 44 RUN TIME 24:49 SKIPSHFT ENA NO SPARK ADV 28 THROTTLE(%) 0 TPS SENSOR(V) 0.49 VEHSPEED(MPH) 0 ------------------------------ FRAME: 4 TM: 14.4 A.I.R. PUMP OFF AC CLUTCH OFF AC EVAP(°F) 20 AC PRESS(PSI) -13.12 AC PRESS(V) 0.02 AC REQUEST OFF BARO("HG) 29.86 BARO(V) 4.82 BATTERY(V) 13.6 LT FUEL TR CL 16 LT FUEL TRM L 160 LT FUEL TRM R 132 EVAP DUTY(%) 0 COOLANT(°F) 177 EGR DUTY(%) 0 EGR VLVPOS 1 ENGINE(RPM) 900 KS COUNTER 2500 FC1 RELAY ON FC2 RELAY OFF IAC POSITION 49 IDLE REQ(RPM) 875 INJ L PW(mV) 4 INJ R PW(mV) 0 KNOCK RET(°) 0 LOOP STATUS CLSD MAF(gr/S) 9 MAP("HG) 16.79 MAP(V) 2.45 IAT(°F) 122 O2S LEFT(mV) 53 O2S RIGHT(mV) 382 RUN TIME 24:53 SKIPSHFT ENA NO SPARK ADV 26 THROTTLE(%) 0 TPS SENSOR(V) 0.49 VEHSPEED(MPH) 0 ------------------------------ DATA SET 2 LT FUEL TR CL 17 LT FUEL TRM L 160 LT FUEL TRM R 160 ENGINE(RPM) 2200 IAC POSITION 86 INJ L PW(mV) 4 INJ R PW(mV) 4 LOOP STATUS CLSD MAF(gr/S) 35 MAP("HG) 24.20 MAP(V) 3.20 IAT(°F) 93 O2S LEFT(mV) 346 O2S RIGHT(mV) 138 RUN TIME 05:36 THROTTLE(%) 32 TPS SENSOR(V) 1.51 ------------------------------ FRAME: 14 TM: 22.6 LT FUEL TR CL 10 LT FUEL TRM L 128 LT FUEL TRM R 125 ENGINE(RPM) 2125 IAC POSITION 90 INJ L PW(mV) 9 INJ R PW(mV) 9 LOOP STATUS CLSD MAF(gr/S) 57 MAP("HG) 18.64 MAP(V) 2.76 IAT(°F) 92 O2S LEFT(mV) 941 O2S RIGHT(mV) 950 RUN TIME 05:37 THROTTLE(%) 27 TPS SENSOR(V) 1.35 ------------------------------ FRAME: 15 TM: 24.2 LT FUEL TR CL 11 LT FUEL TRM L 127 LT FUEL TRM R 125 ENGINE(RPM) 2475 IAC POSITION 90 INJ L PW(mV) 4 INJ R PW(mV) 4 LOOP STATUS CLSD MAF(gr/S) 63 MAP("HG) 17.77 MAP(V) 2.71 IAT(°F) 90 O2S LEFT(mV) 204 O2S RIGHT(mV) 857 RUN TIME 05:39 THROTTLE(%) 30 TPS SENSOR(V) 1.43 ------------------------------ FRAME: 16 TM: 25.8 LT FUEL TR CL 11 LT FUEL TRM L 125 LT FUEL TRM R 123 ENGINE(RPM) 2700 IAC POSITION 90 INJ L PW(mV) 9 INJ R PW(mV) 9 LOOP STATUS CLSD MAF(gr/S) 82 MAP("HG) 19.73 MAP(V) 2.90 IAT(°F) 89 O2S LEFT(mV) 799 O2S RIGHT(mV) 391 RUN TIME 05:40 THROTTLE(%) 27 TPS SENSOR(V) 0.98 ------------------------------ FRAME: 17 TM: 27.4 LT FUEL TR CL 17 LT FUEL TRM L 160 LT FUEL TRM R 160 ENGINE(RPM) 2450 IAC POSITION 88 INJ L PW(mV) 0 INJ R PW(mV) 4 LOOP STATUS CLSD MAF(gr/S) 39 MAP("HG) 17.44 MAP(V) 3.41 IAT(°F) 89 O2S LEFT(mV) 724 O2S RIGHT(mV) 462 RUN TIME 05:42 THROTTLE(%) 31 TPS SENSOR(V) 1.43 ------------------------------ FRAME: 18 TM: 29.0 LT FUEL TR CL 11 LT FUEL TRM L 124 LT FUEL TRM R 122 ENGINE(RPM) 2250 IAC POSITION 90 INJ L PW(mV) 9 INJ R PW(mV) 9 LOOP STATUS CLSD MAF(gr/S) 52 MAP("HG) 16.79 MAP(V) 2.39 IAT(°F) 89 O2S LEFT(mV) 977 O2S RIGHT(mV) 977 RUN TIME 05:44 THROTTLE(%) 19 TPS SENSOR(V) 1.08 ------------------------------ FRAME: 19 TM: 30.6 LT FUEL TR CL 7 LT FUEL TRM L 159 LT FUEL TRM R 137 ENGINE(RPM) 2100 IAC POSITION 84 INJ L PW(mV) 4 INJ R PW(mV) 0 LOOP STATUS CLSD MAF(gr/S) 24 MAP("HG) 11.56 MAP(V) 1.51 IAT(°F) 89 O2S LEFT(mV) 235 O2S RIGHT(mV) 471 RUN TIME 05:45 THROTTLE(%) 11 TPS SENSOR(V) 0.84 ------------------------------ |
Usually if you bring the rpms up at idle to about 2500-3k (No vacuum in motor) and your o2 readings come down to desired value, that indicates a vacuum leak. Not saying its the case here, just something to test.
IAC position seems high, iirc around 30-40 at idle was desired. Is it an aftermarket throttle body? Intake manifold? Try doing an IAC reset and see if anything improves there. I'd say clean the MAF for ****s and giggles. Stock cars, the motor displacement roughly equates the grams/second flow rate. Never looked at a modified car and I'd assume it would flow more, just something I noticed. Smelling rich and having lean codes present doesn't make sense to me. Wonder if you are having ignition issues. The o2's seems to be switching, we want to see the voltages swing from under .5 volts to over .5 volts. They are constantly helping to adjust afr. |
a little background. It was a rebuilt LT1 - 355, probably about 30k on the motor. Added a CC306 with all the necessary valve train components, stock TB, stock heads, stock intake. Long tubes, no emissions - tuned by Brian from PCMforless. Car ran excellent for a couple years until now, so it's something that recently failed.
I was thinking about taking the whole TB off and cleaning everything including MAF. I just assumed I would have gotten a MAF trouble code if that was an issue but never assume, right? |
Yeah, never assume. I would definitely give it all a good cleaning and reset the iac. No egr, correct? I'd still try looking for a vacuum leak as well.
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Will do, thanks. And correct, no egr
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What year LT1?
Are you running MAP and MAS? CHave you checked the PVC isn't stuck? |
1995 LT1
MAP and MAF Haven't checked the PCV. Hoping to get back to this this week. |
Some updates:
I worked on fixing the collector leaks and also found some loose header bolts. I then started checking all the rubber and found a split in the small hose coming from the left of the intake that goes to the Opti (not sure if this a source for vacuum leak). Checked the PCV valve, it is not stuck but the grommet where it fits into the intake manifold is completely deteriorated and split. (also looks like a lot of oil moving through there - might pick up a catch can) The nub caps on the TB for the coolant bypass are also cracked all the way through (also not sure if this can be a source for vacuum leak) Thanks for all the advice, I'll be ordering some parts and reporting back.. |
sounds like everything that can cause a lean code. Good hunting!
the TB coolant bypass will not cause a vacuum leak as that is only a coolant port :) |
Final update for anyone following or if a search takes them here with similar problems. I wasn't throwing a code anymore but it still wasn't right and I hit a wall. I took the car to Josh (JS Performance) and the newer style (plastic) Delco MAF was causing whacky readings as well as a worn out throttle body main assembly. I couldn't see this on my scanner but Josh saw at idle the TPS voltage was jumping around. The computer was correcting false readings and throwing off fueling. Factory style metal Delco MAF and a BBK throttle body and the car is running great! He also did the caster/camber plates and a few other things while I had it there. I picked the car up Friday and have driven it about 100 miles so far.
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