Quick opti diagnostic question

[FTA1995]

When and if the pcm throws the Hi res fail code, can that be caused by an intermittent wiring problem between the opti<-->pcm? Could have been from a mouse this winter, or a beat up connector maybe if thats the case...

Yea I know, stupid questions ask for stupid answers

Thanks again in advance guys

[Injuneer]

Yes, can be caused by deterioration of the short Opti harness from the passenger side of the intake manifold to the Opti. Check the connectors on both ends for corrosion and damaged pins. Obviously, it can also be a problem with the optical sensor.

If you find you need a new harness, there are places to get them way cheaper than dealer prices. EFIConnection is one source.

[FTA1995]

Checked everything from the PCM pins to the first connector to the small harness, the small harness itself, and the PCM pins too the end of the small harness connector, multimeter says it's all good, shook it as much as I could to see if it was an intermittent problem. Found something interesting; the high res signal wire near the PCM was stripped a bit, probably for a oscilloscope probe, I know he had some kind of problem with the opti system and didn't know much about it. I re taped the section while I was there, I'm really doubtful that caused the problem. I took apart the old opti, cap and rotor were great still, even the optical side looked fine. The steel disk looked a little distorted, otherwise no sign of damage. Guess it's just another replacement again, this time I'm going to take the new one apart and rtv the seals to ensure a leak proof seal.

[Injuneer]

How often does the code for loss of high res pulse pop up? The engine will run without it - just a very minor loss in spark timing accurady (increased "spark scatter"). Clear the code (pull "PCM BAT" fuse for 30-seconds) and see how quickly it comes back.

The problem I had with the optical module was rust particles getting in the LED's that pass the light through the slots in the metal disc. Buy my Opti was an unvented unit, with the problem of accumulating ozone causing the excess rust. You need to make sure the vent system is working. The vent wasn't added to eliminate moisture, it was added to eliminate the ozone generated by the high voltage spark in the cap.

Even though the pulse signal is low voltage (0-5V) I'd wrap the bare spot on the wire with electrical tape.

[FTA1995]

I did tape the exposed section up, I check the vacuum side of the vent when I change the oil, I think I might need to get a new vacuum regulator(that plastic thing in line between the opti and manifold vacuum). The side of it melted after ending up in contact with the driver side header, although it doesn't leak air. I did notice, however there was a thin coating of rust inside the opti side Of the distributor, very little but I thought it was strange without te slightest evidence of moisture. How much rust are we talking about as far as sensor interruption? The disk was completely clean, there was some noticeable oxidation along the surface of the cast plate. Maybe enough to warrant a ventilation restriction. I swear, when I find the resources I'm going to redesign this damn thing to be more reliable, but that might be a pipe dream.

[FTA1995]

Fred;
Missed your original question, This is the first time I have ever experienced a running code with a problem opti. The usual case for me is just an extended start time quickly followed up with a stall that isn't fixed until the next distributor goes in. I'm letting the rtv cured on the water pump right now; the new opti is in. I had no choice but to buy mine from summit I just don't have the money to throw at a GM unit. I did take the time to seal the new one up pretty well, along with a full check of the vent harness from fresh air inlet to manifold vacuum. The vacuum side checked out fine, the check valve is good, and the vacuum regulator is good as well.

Another question; is there anyways to tell the difference between a Mitsubishi optical sensor and the less desirable unit? I've read many people say the Mitsubishi eyes are more reliable than the other options.

Thanks again,

[Injuneer]

I've only seen GM Optis, and the sensor has a Mitsubishi 3-diamond emblem on it.

[FTA1995]

The only one I've seen that on was the first opti that came with the car. The gm performance parts model has it? Does that make it worth the extra 100 bucks over the summit unit for example...

[Injuneer]

I'm not sure. I haven't looked at an Opti in years, but both mine had the Mitsu logo - original unit and the vented GM unit I bought for the stroker in 1999. I doubt there is any difference between the Delphi unit you buy from just about anywhere, and the GM Performance Parts unit.

The issue with non-Delphi Optis seems to be the failure rate, and my opinion is based only on feedback I see on the many LT1 sites I visit. A brand new Delphi can fail. An MSD can fail. The non-Delphi units seem to fail in inverse proportion to their cost. A $60 unit from eBay has a life expectancy of minutes. The Summit unit is probably in the middle somewhere, with regard to failure rate, but its all very unscientific..... just reading posts on the Internet.

My hands-on LT1 days are over. Its just what I read.

[FTA1995]

I understand what you mean, and I can't wait for the day I can say my hands on lt1 work is over myself. Hopefully my summit unit will last more than a year, after that I'll take my final stand with the gm unit.
Thanks for the help