50chevy
June 24th, 2010, 03:42 PM
I posted this question on another forum to no avail. Here are a few excerpts of my posts but no one had ever seen this before and did not give sure answers. The local tuning shop is using EFI live for the tuning with OS 3. I am not really experienced with tuning but I can contact the shop for any tune details that may be needed to solve this dilema. Basically the o2's work on a cold engine with the key on, once the motor is started they stop responding. The wiring is guaranteed to be correct, I personally built the harness and it has been verified by others.
Engine Specs:
408 ci ls1
Siemens 60 lb/hr injectors
Speed Density tune
4l65e auto trans
no vats/rear o2/emissions
Post #1
I could write a novel on how these o2 sensors have driven me crazy. I have a 408 ls1 stroker in a 1950
Chevy truck and have deleted all emission items and rear o2 sensors. I have had a local professional tuner come to my house for the third time to baseline tune my truck so I can break-in the new motor and trans before it goes to be dyno'd. The truck runs and all sensors have signal input to the PCM. The o2 sensors flatline at 450 mV. So I swapped the sensors, same result. Then I completely removed the 02 sensor wiring and put in a new o2 sensor harness with its own dedicated ground and ignition power. This morning we plugged a TECH II scanner into the truck and turned the ignition on. We got a signal: 300mv, 700mv, moving around, and so on. He wrote a new OS (Efi-Live System #3 ?) and started it. The same result, no o2 signal, flatline at 450 mV. I am desparate here, this has kept me from about 3 months of car shows and I just want to drive my truck. We did try swapping PCM's but it made no difference. Any help would be appreciated. Questions are welcome if I need to be more specific. Thanks!
Post #2
When the engine was cool, I did not have a scan tool available to me te other day, but I put a multimeter on the purple signal wire and it went above 700 mV when I turned the ignition on. Then this morning we turned the ignition on (cold engine) with a TECH II plugged in and it confirmed that it had a signal. Once we got the engine running, EFI Live showed 450 mV and the TECH II confirmed that.
Post #3
I just did the "manual" o2 heater test by removing them from the pipes and feeling them with the key on. In about 30 seconds, they were very hot. Both sensors responded the same way. To answer the question about the o2 to PCM wiring, I replaced both purple and tan wires all the way to the PCM and crimped new pins on the end. The o2 wiring is completely new. Keep the comments rolling in, believe me, I really appreciate every single comment.
Engine Specs:
408 ci ls1
Siemens 60 lb/hr injectors
Speed Density tune
4l65e auto trans
no vats/rear o2/emissions
Post #1
I could write a novel on how these o2 sensors have driven me crazy. I have a 408 ls1 stroker in a 1950
Chevy truck and have deleted all emission items and rear o2 sensors. I have had a local professional tuner come to my house for the third time to baseline tune my truck so I can break-in the new motor and trans before it goes to be dyno'd. The truck runs and all sensors have signal input to the PCM. The o2 sensors flatline at 450 mV. So I swapped the sensors, same result. Then I completely removed the 02 sensor wiring and put in a new o2 sensor harness with its own dedicated ground and ignition power. This morning we plugged a TECH II scanner into the truck and turned the ignition on. We got a signal: 300mv, 700mv, moving around, and so on. He wrote a new OS (Efi-Live System #3 ?) and started it. The same result, no o2 signal, flatline at 450 mV. I am desparate here, this has kept me from about 3 months of car shows and I just want to drive my truck. We did try swapping PCM's but it made no difference. Any help would be appreciated. Questions are welcome if I need to be more specific. Thanks!
Post #2
When the engine was cool, I did not have a scan tool available to me te other day, but I put a multimeter on the purple signal wire and it went above 700 mV when I turned the ignition on. Then this morning we turned the ignition on (cold engine) with a TECH II plugged in and it confirmed that it had a signal. Once we got the engine running, EFI Live showed 450 mV and the TECH II confirmed that.
Post #3
I just did the "manual" o2 heater test by removing them from the pipes and feeling them with the key on. In about 30 seconds, they were very hot. Both sensors responded the same way. To answer the question about the o2 to PCM wiring, I replaced both purple and tan wires all the way to the PCM and crimped new pins on the end. The o2 wiring is completely new. Keep the comments rolling in, believe me, I really appreciate every single comment.