lt4red

I have an issue with my 96. It is the ignition cutting out and the car dying. It's very random, sometimes it will come right back, others I have to sit on the side of the road and wait for a minute. I've tried to troubleshoot this problem, but it is very intermittent, and runs great any other time. I do know for sure it is the ignition I'm losing, but I get no codes. I was wondering if anyone knows, is it possible for you to lose the low res pulse from the opti, as this would cause my problem, yet get no codes from the error. I found the code I would get from the service manual, but it isn't setting one, so I'm at a loss. I suspect the low res signal, because I sometimes lose the tach, and it will stay dead, even when the engine comes back to life. The tach gets it's feed from the pcm, which calculates the tach signal based on the opti low res input. Anyone?

tjwong

It is possible as I have seen it several times. First thing to check is the opti harness. Remove it from the opti and check the terminals for corrosion, if they are corroded they will appear green in color, check both ends. If nothing is found and if that is the original opti the opti would be the next in line as a suspect.

Redeasysport

One other thing to consider is the ICM. It can have an intermittant problem and not toss a code.A bad tach filter will also cause this problem. If it shorts to ground it will kill the ignition.

lt4red

I've had the Icm tested, but who knows if that was done correctly, but the 96 has no tach filter. It was changed. The manual will show it in some scematics, but it is not there. They changed the tach signal to an input from the pcm for 96.

Corsaab

Its very simple to diagnose a bad opti with oscilloscope.
Following link shows low resolution pulses on my 94 LT1.
I connect the oscilloscope to the harness connector under the right
fuel rail cover.
Its gives me 12 V, ground, high resolution pulses and low resolution pulses.

The number 1,2,3 represent missing pulses from narrow slots in the
rotor (cylinder and cam recognition).

PCM loose counting and start to firing wrong cylinder, and i have misfire, hesitation, stumbling, pinging and so on.
This started long before engine go into closed loop, about 70 C.

http://web.telia.com/~u33227289/Opti...g_pulses_2.jpg

That missing pulses NEVER set any DTC codes for me DTC 16, 36.

DTC 16 = 720 high resolution without low resolution pulses: NO CHANCE

DTC 36 = 40 low resolution pulses without high resolution pulses: NO CHANCE

Optispark is still in my car, more to come...............

Sorry for my bad written english

Kjell

Redeasysport

Nice screen capture on the "O" scope. I think for the code to set it needs to see no pulse for a period of time not just random losses.It sure seems like that waveform could cause problems though. I wonder how many of our cars that idle poorly have the same one?

lt4red

Maybe this is bogus, and I'm not familiar with its use, but I've read online that the pulses off the opti are coming way too fast to get anything meaningful with an o-scope. Not true?

Redeasysport

Not true. An "O" scope can be set to read pulses many times faster than an opti. You just select the proper frequency and amplitude on the dials.

lt4red

Thanks for the response everyone, I have a friend with a scope and will ask him about using it, but will I get anything out of whack if it is running smooth when I test it?

MikeC4

I would love to see an "O-scope" capture of a properly working Opti. Do you plan on replacing this Opti, as I am sure the car must run like crap with this missing low resolution pulses....

MikeC4

Very "not true". There are scopes that can capture in the Giga Hertz range nowadays. These new scopes can easily capture the 360 high resolution pulses as well.

tjwong

You don't need a high end scope to catch a Opti screw up. Anything that can capture at speeds greater than 20mhz is more than enough to analyze an opti wave form. I got an old Fluke portable that is at 16mhz and it even works fine as long as its properly setup. A 1ghz and up scope is still quite expensive.

Corsaab

Only a digital storage oscilloscope will work at this case.

I have a Tektronix TDS 220 with software for pc.

I can download a screenshot from my oscilloscope to pc and
there analyze every millisecond of the Optispark pulses.

Kjell

lt4red

Will an opti that is not visibly causing a running problem still show missing pulses if it's on it's way out?

lt4red

Will I be able to learn anything if I am unable to store the image and review it later? I think I can only watch the screen on his oscilloscope, no screenshot storage.

Corsaab

Yes, a well trained eye can se missing pulses, but thats mutch mutch easier to se on a digital oscilloscope.

Her is pictures of the connections:

http://web.telia.com/~u33227289/opti_connect_1.jpg
http://web.telia.com/~u33227289/opti_connect_2.jpg

Kjell