Bad Opti?
03-24-2016, 01:17 PM
#1
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Thread Starter
Join Date: Sep 2000
Location: Central Valley, Ca
Posts: 22
Bad Opti?
Hi all.
After replacing the fuel pump in my Z28 a couple of weeks ago, the car was running great. Yesterday driving to work, the car suddenly lurched and I thought the engine had died ; the tachometer was at zero. As I started to pull to the shoulder, I realized I still had power steering and the car was still running. I went on to work and parked it. When I tried to start it, it would crank but not start. I read some threads on here at lunch and found a couple where a car would start after about 10 seconds of cranking, so I tried that and it worked. It started again after work, so I drove it home monitoring it with Torque software. All the sensors showed the same values as it has since the new fuel pump (MAF,MAP,FT,etc). I also have a P0372 code now. I did more reading on here and elsewhere and the long start and dead tach, and code sound like there is no hi-res signal from the opti. I planned to run some tests this morning but got called to work. Maybe tomorrow. Does this sound like it could be anything BUT the opti? The weird thing is that I had the opti replaced at about 96K miles and am now at 192K - almost exactly double.
I have read a LOT of threads on replacement optis, and most people recommend AC Delco or Delphi ONLY. Looks like the delco is no longer available new, and the rebuilt might not have the Mitsubishi sensor. I just sent a mail to Delphi to see if they would tell me what brand of sensor their new unit ($400) uses. If it turns out there is no way to get a new Mitsubishi sensor, is there a second choice? I see I can buy a sensor only from AIP. Has anyone used any of their products?
Am I harming the engine by running it this way? There is no misfire code and it feels like it's running fine once it starts.
TIA for any info or advice.
Leon
After replacing the fuel pump in my Z28 a couple of weeks ago, the car was running great. Yesterday driving to work, the car suddenly lurched and I thought the engine had died ; the tachometer was at zero. As I started to pull to the shoulder, I realized I still had power steering and the car was still running. I went on to work and parked it. When I tried to start it, it would crank but not start. I read some threads on here at lunch and found a couple where a car would start after about 10 seconds of cranking, so I tried that and it worked. It started again after work, so I drove it home monitoring it with Torque software. All the sensors showed the same values as it has since the new fuel pump (MAF,MAP,FT,etc). I also have a P0372 code now. I did more reading on here and elsewhere and the long start and dead tach, and code sound like there is no hi-res signal from the opti. I planned to run some tests this morning but got called to work. Maybe tomorrow. Does this sound like it could be anything BUT the opti? The weird thing is that I had the opti replaced at about 96K miles and am now at 192K - almost exactly double.
I have read a LOT of threads on replacement optis, and most people recommend AC Delco or Delphi ONLY. Looks like the delco is no longer available new, and the rebuilt might not have the Mitsubishi sensor. I just sent a mail to Delphi to see if they would tell me what brand of sensor their new unit ($400) uses. If it turns out there is no way to get a new Mitsubishi sensor, is there a second choice? I see I can buy a sensor only from AIP. Has anyone used any of their products?
Am I harming the engine by running it this way? There is no misfire code and it feels like it's running fine once it starts.
TIA for any info or advice.
Leon
03-25-2016, 01:25 PM
#2
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,648
Re: Bad Opti?
DTC 0372 is for the high resolution pulse signal. The engine can run without that signal. The PCM will default to running only on the low resolution signal, and the only difference will be a small loss of accuracy in ignition and injector timing. You would be very unlikely to even notice the difference. Clear the code and see how fast it returns.
The real problem with the high res signal is when it becomes corrupt, and can cause issues with the misfire detection and cause the engine to run rough and make the tach erratic. Not sure, but misfire detection may be disabled when P0372 sets. Can't see any reason why continuing to drive the car could be causing problems.
P1371 is the fatal low res code, that will shut down the engine. Since you don't have that code, that is not what caused the problem. You should still have a working tach.
Check the Opti harness connectors to make sure they aren't loose, or corroded.
AIP is the new name for "All Ignition Products". Their Opti's were real disasters maybe 10 years ago when they tried to sell them as some sort of major improvement over the stock units. Total junk.
People are still buying the remanufactured AC Delco unit, and I haven't seen any increase in reported failures for AC Delco, but maybe not enough time has passed to start seeing a problem evolve.
The real problem with the high res signal is when it becomes corrupt, and can cause issues with the misfire detection and cause the engine to run rough and make the tach erratic. Not sure, but misfire detection may be disabled when P0372 sets. Can't see any reason why continuing to drive the car could be causing problems.
P1371 is the fatal low res code, that will shut down the engine. Since you don't have that code, that is not what caused the problem. You should still have a working tach.
Check the Opti harness connectors to make sure they aren't loose, or corroded.
AIP is the new name for "All Ignition Products". Their Opti's were real disasters maybe 10 years ago when they tried to sell them as some sort of major improvement over the stock units. Total junk.
People are still buying the remanufactured AC Delco unit, and I haven't seen any increase in reported failures for AC Delco, but maybe not enough time has passed to start seeing a problem evolve.
03-26-2016, 02:35 PM
#4
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Thread Starter
Join Date: Sep 2000
Location: Central Valley, Ca
Posts: 22
Re: Bad Opti?
Thanks to both of you for responding. Is it safe for me to check the harness with a DVOM by backprobing the connectors? I don't want to damage the pcm. I'm not sure if it will help much. It seems I would need an oscilloscope to tell if there's a signal and not just voltage.
Leon
Leon
03-26-2016, 03:16 PM
#5
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,648
Re: Bad Opti?
If the Opti is producing the required signals, you should be able to detect the spark signal to the ICM. Shoebox has a procedure:
4th Gen LT1 F-body Tech Articles
Note that in the first sentence, the code references should be low res - DTC 16 (OBD-1), P1371 (OBD-2); high res - DTC 36, P0372.
To check at the Opti harness connector (can be tested at the gray connector on the bracket on the passenger side of the intake manifold), using a high impedance digital volt meter (DC volts), you should have 12V on red wire (pin C - Bat voltage from Opti); near 0V on pink/black (pin D - ref ground from Opti); and as you slowly rotate the engine the voltage on red/black (pin A - low res pulse) should slowly switch between 0-5V, and the purple/white (pin B - high res pulse) should switch rapidly between 0-5V.
4th Gen LT1 F-body Tech Articles
Note that in the first sentence, the code references should be low res - DTC 16 (OBD-1), P1371 (OBD-2); high res - DTC 36, P0372.
To check at the Opti harness connector (can be tested at the gray connector on the bracket on the passenger side of the intake manifold), using a high impedance digital volt meter (DC volts), you should have 12V on red wire (pin C - Bat voltage from Opti); near 0V on pink/black (pin D - ref ground from Opti); and as you slowly rotate the engine the voltage on red/black (pin A - low res pulse) should slowly switch between 0-5V, and the purple/white (pin B - high res pulse) should switch rapidly between 0-5V.
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