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Discussion Starter #1
Been having a o2 problem as well as a misfire on the driver side for a long time even after replacing almost all of the ignitions components.

Been trying to trouble shoot for a while and im not sure what else there is besides the ecm.
Tested everything and gathered data threw tunerPro
(Things ive checked and tested)
-Both sensors replaced
-Driver side stays stuck at 450.mv, Left works properly
-Swapped sensors to opposing sides and problem stayed on driver side
-Rewired Driver/Passenger to ecm (wires looked burnt and cut up)
-Driver side still wouldn't read(stuck at 450mv)
-Grounded out both side to check wiring(Driver side still would not read or move Mv) [passenger side works and reads 4mv when grounded]
-Re did o2 sensor ground to frame
-checked again and Driver side o2 would not read Stuck at 450mv


Im not sure what else could be causing this not to read or register. This has been causing a misfire and has been giving me a headache since i got the car. The misfire doesn't start until around 180* im assuming because the car is stuck in open loop and that sensor isnt reading right.

Any help id greatly appreciate it. Thanks! 1992 vette
 

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You can download 93 4th gen f-body service manuals at the following link The manuals will have full wiring diagrams and troubleshooting help.
www.mediafire.com/?40mfgeoe4ctti

Of course 92 vette service manual would be the best. But f-body would help.

Since you switched o2 sensors from side to side and problem stayed on driver side, you should check the wires for continuity. This involves removing ecm connector and os connector and testing wires. Also check connectors for bent, corroded, or loose pins.

You could very well have a bad o2 driver in your ecm. But since ecm's are expensive I would hate to buy one and find it didn't fix the problem. I always keep a known good spare computer for my cars. That way I can do a quick change out to see if problem is solved.

Lets get to the ignition. If you changed opti with anything other than a GM, Delco, or Delphi opti, it is junk. Do yourself a favor and invest in a $70 PC based oscilloscope. And learn how to use it.

Use it to check the low & high resolution square wave pulses that opti sends to ecm. If you bought any opti other than the 3 I mentioned earlier, there's a high chance of you having an opti problem.

If you changed you icm and didn't put heat sink compound on it and it's heat sink, icm could be having problems.

Codes for opti & icm do not light the cel / ses lifght.
 

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Discussion Starter #3
checked threw the service manual and did find some information but nothing related to no signal to the ecm. Most of it is either rich or lean conditions or open/closed circuit based off the sensor itself. I also did some more trouble shooting i pulled the wire out again to check for continuity and showed good, as well as took the sensor out and bench tested it. That was showing proper voltage ranges. ( grounded the o2 sensor and lightly hit it with a torch to view different voltage .20v-1v)

So i tested the wire that shows good, the sensor itself is good, there isn't another circuit connected or related to the 02 sensor its a straight shot from sensor to the ecm. But still based off data im receiving there is no signal to the ecm.

Im fairly confident that the misfire/ shutter has to be because of that not working 02.. It starts around 180* every time(which is the area when the cars open/closed loop timer runs out) and i can predict it. since i got the car the misfire has been there at idle but higher in the rpm above 2k ish it is gone. Things i have replaced along the way
opti (delco as well as switched to a reme and problem is still there)
Coil(msd and moroso)
Plugs (ngk)
Plug wires (Taylor)
fuel pump (bosh)
Fuel filter
Fuel regulator
icv
Fuel injectors(fuel injector connection)
Egr valve(new but deleted)
maf
Purge solenoid/air pump (deleted but new)


I have tuning capabilities so i can as well disable and enable most of the components such as egr/air and even after that it still stays.

As far as i know the only things i haven't replace in the ignition and fuel area is the icm and ecm. I don't see a benefit in replacing it based off (from what i know it has no relationship to the o2 sensor problem/ a bad icm could cause false readings).

Im not sure there is much more i can do to figure this out. Im at the point of wanting to either replace the entire on board computer system or just trying to disable closed loop to see if it has any affect.
 

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checked threw the service manual and did find some information but nothing related to no signal to the ecm. Most of it is either rich or lean conditions or open/closed circuit based off the sensor itself. I also did some more trouble shooting i pulled the wire out again to check for continuity and showed good, as well as took the sensor out and bench tested it. That was showing proper voltage ranges. ( grounded the o2 sensor and lightly hit it with a torch to view different voltage .20v-1v)

So i tested the wire that shows good, the sensor itself is good, there isn't another circuit connected or related to the 02 sensor its a straight shot from sensor to the ecm. But still based off data im receiving there is no signal to the ecm.

Im fairly confident that the misfire/ shutter has to be because of that not working 02.. It starts around 180* every time(which is the area when the cars open/closed loop timer runs out) and i can predict it. since i got the car the misfire has been there at idle but higher in the rpm above 2k ish it is gone. Things i have replaced along the way
opti (delco as well as switched to a reme and problem is still there)
Coil(msd and moroso)
Plugs (ngk)
Plug wires (Taylor)
fuel pump (bosh)
Fuel filter
Fuel regulator
icv
Fuel injectors(fuel injector connection)
Egr valve(new but deleted)
maf
Purge solenoid/air pump (deleted but new)


I have tuning capabilities so i can as well disable and enable most of the components such as egr/air and even after that it still stays.

As far as i know the only things i haven't replace in the ignition and fuel area is the icm and ecm. I don't see a benefit in replacing it based off (from what i know it has no relationship to the o2 sensor problem/ a bad icm could cause false readings).

Im not sure there is much more i can do to figure this out. Im at the point of wanting to either replace the entire on board computer system or just trying to disable closed loop to see if it has any affect.


I had a similar running problem with mine. If the car sat for 4-5 hours, it would miss terribly for the first few miles, then just like clock work, it would start running normally again. I tested everything I could think of, changed a lot of parts. Finally I decided to throw in new O2 sensors. That fixed my problem! They tested as good, but they were causing the problem.
Bill
 
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