The experts are wrong again.
I had cylinders 1,7,2 with cold header tubes, ie engine missing badly. I added a delteq, which also went thru its diagnostics and thought the opti signal was ok.
I just put a new opti in and the engine runs smooth and all header tubes are hot.
My opinion is the hi/lo signals can be in sync and still cause individual cylinders to miss/ be mis-timed.

 

This would certainly explain the infamous "random miss" but it sure leaves the "why" question unanswered. Any ideas anyone?

 

I wonder if there was some impairment at those particular positions on the shutter wheel...

 

Dissect it!

 

You need a healthy Opti for the Delteq. If the bearing was loose, slots blinded, etc., it would certainly screw up the pulse pattern, and cause misifires..... who said the Opti can't cause individual cylinders to misfire?

 

No one told me the opti could cause individual dead cylinders. After multiple postings on this board and talking to Jim at Elite Spark Plugs, I was convinced that the opti was either in sync or not. If not in sync a random miss or other driveability issues which we've all seen would show up. But if the Delteq diagnostics said the opti hi/lo signals were present and in sync, then the opti side hi/low was good. This does not appear to be true.
An additional oddity is that my 3 dead cylinders were getting visible fire at the plugs. And those cylinders plugs would get black and soft sooty - almost like the timing of spark was to early or late for proper combustion. The car ran pig rich due to poor combustion in those cylinders. Any one on this board ever hear of an LT1 running rich for no obvious reason? Did we need another reeason to dislike/mistrust the opti?

I have not taken the opti hi/lo side apart, mainly because I cannot find a bit small enough to get the rotor screws out. The cap/rotor appear to be ok, other than the #8 wire lead on cap is rusted/burned/corroded into almost being completly gone - but #8 was still firing .

 

With three cylinders missing, I would have thought the Delteq LED would start blinking because it lost "synchronization."

Because cylinders 7, 2, and 1 are sequential in the firing order, which would be a significantly large gap with no firing (assuming the problem wasn't intermittent), one would think that should be sufficient to set an ECM trouble-code and cause the Delteq diagnostic LED to start blinking.

Do you have sequential or batch-fire injection?

Tom Piper

 

I posted awhile ago about a opti proplem I had. The same thing happened to me. The car was running and died. Found out the rotor destroyed itself(normal). So I changed the cap and rotor. Well started it up and sure enough the car was pig rich, couldnt even breath in the garage. Missing really bad. Clyinders 6,8,7 were cold on the header. Well after looking at the install agian, which was right. I took the opti apart. Looked like the shutter wheel was not straight. So I didnt even bother to put it back on. Got a whole new opti and it ran great. Turns out that either the optical sensor was hit by the shutter wheel or the optical sensor too a crap.

 

I have a 94, and am not sure, but I think it is sequential.
I didn't know those three were in sequence, that was a hell of good clue. I asked delteq repeatly if that type of error was possible, and told absolutely not. My red LED stayed on steady.

 

I'm not questioning your analysis, but going strictly by logic to draw a conclusion, it would seem your problem was fuel-injection related (a '94 is sequential) and not caused by the opti-signals. Both the Delteq LED AND the ECM detected no problem with those signals. It seems highly unlikely that the Delteq diagnostics would allow 3 cylinders in a row to not give a low-res pulse and not lose synchronization. If it does.......

I'd be tempted to send the defective Opti-Spark to Delteq and let them test it.


Tom Piper

 

I have an additional thought on this:

Did you have the same problem before the Delteq install?

If not, the Norhtstar coil pak has an input called "bypass." Its main purpose in a Cadillac is to allow the use of the crankshaft position signals, instead of the ECM EST signal, to fire the ignition, with a fixed advance of 10*, if the system goes into "limp home mode."

I am not sure if the Northstar is the same, but the LT5 has the same setup; and, if the LT5 "bypass" input falls below a certain point (a low signal tells the ignition module to go into "limp home mode") the module affectively pulls the EST signal to ground level (in other words, shorts if out) for that period of time.
So, assuming it's the same, if the Northstar coil pak input to the "bypass" were somehow not connected well, it could eliminate the ECM ignition signal (EST signal). And, from what I am told, the Northstar coil pak does not recover immediately for the next few cylinders when the "bypass" goes back to normal.
If true, this would account for the Opti signals being OK and the Delteq functioning properly, but the Northstar coil pak not firing the plugs.
But, the fly-in-the-ointment is this "bypass" signal would have to be pulled low (or eliminated) in sequence with the same engine position for every other revolution. If you have the Delteq wiring schematic, look at the wire that goes to the "bypass" terminal and make sure the connector is plugged in correctly and the wire is not damaged.

But, then, this would not account for putting on a new Opti-Spark solving the problem, unless the wiring the Northstar coil pak were disturbed.

Tom Piper

 

I had the problem before and after the Delteq.
Someone said the opti signals also triger / time the fuel injection, if so then maybe the injectors were goofed up also. I tested them with a noid light and it did flash on the dead cylinders - is that all there is to the test?
I also saw spark at those spark plugs. Is it more of a timing issue, the timing of the spark vs the fuel. Maybe they were getting spark and fuel but the timing was off. The plugs were showing a sooty deposit indicating some type of weak combustion.
The delteq instructions didnt say anything about the Northstar safe system.

 

A weak spark or lean fuel mixture can cause missing also.

Since you had the problem before the Delteq, it wasn't the Northstar system.

The Opti signals are used for camshaft and crankshaft position sensing.

For the stock ECM:
The low-res pulse is used for both the fuel injection timing, the ignition timing, and to tell the ECM the engine speed. Without the low-res pulse, the ECM has no way to determine which cylinder is coming to top-dead-center and will not run.
The high-res pulse is used to refine the ignition timing (not fuel injection timing) by giving the crankshaft position within one degree accuracy. Without the high-res pulse, the engine should still run, but at reduced performance and a trouble-code should set.

When the Delteq is added, everything is the same as above.
But, the low-res signal is now used to also tell the Delteq which NorthStar coil to enable to be fired by the EST (ignition timing signal) from the ECM. The ECM still has control of the ignition timing with the Delteq system.

Tom Piper

 

Thanks for all the great posts!
Sounds like the high res signal must have mis timed 1,7,2 enough to cause poor combustion, but operating good enough to not set a code. The delteq did not see an error either. Rathmotorsports.com post above also saw this same situation.
To summarize, the opti hi res signal can cause individual cylinder timing errors that can signficantly affect performance. If timing were slightly advanced in certain cylinders pistons could burn if blown. Scary if correct, Halloween anyone?

 

I would like to know also, because I've never heard anyone say that. I had a miss that was intermittent, then got worse and ended up a dead miss. I checked the header primaries and #7 was cold. I was getting a signal to the injector, the plug wire checked out ok, so I replaced the opti and it solved the problem.