Stumble due to possible RFI?

[firebird_1995]

I'm having an issue with what I'm calling a "stumble" but looks like a signal loss on the datalog. I've edited out 8 points in the log where it did it on a 45 minute cruise. In searching for similar posts the closest thing i see is when people are having issues with VR cam sensors. The engine goes from 2000 rpm to 3, and back to 2000 in just a few frames. You can feel it in the car when it happens. I've only noticed it at cruising speeds but haven't done a whole lot of higher rpm tuning yet. I'm getting ready to go log a composite ignition log now (forgot to click save to file yesterday) but in the logs I don't see any "loss of sync" errors.
Details of the setup are;
95 LT1 engine using the optispark as a crank/cam sensor, D581 gen 3 coil packs, using TS MS ultra 3.0.22, ms3 pro 1.5.0 release.

2017-08-05_07.49.34.msq

stumble1.msl

stumble2.msl

Thanks

[firebird_1995]

stumble3.msl

stumble4.msl

stumble5.msl

[firebird_1995]

Here are a few other threads that seem similar to mine. It looks like this stupid optispark may be the cause. I may just convert over to a 24x signal and be done with it. Here is a composite ignition log for anyone interested.
http://www.msextra.com/forums/viewtopic ... 0&p=484789
http://www.msextra.com/forums/viewtopic ... 6&p=367381

ignlogsmaller.zip

[firebird_1995]

Another thread with an identical issue. Particularly noteworthy is that this OP said that he could pretty much plan on getting the rpm dip between 1900-2300 which is where I see my issues.
http://www.msextra.com/forums/viewtopic.php?t=50826

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[billr]

Just so you don't feel abandoned, some of us are following this thread, but I have no experience with the optispark so can't really help. Like you, my perception from reading here is that the optispark is less than, well... "optimum".

[firebird_1995]

Just so you don't feel abandoned, some of us are following this thread, but I have no experience with the optispark so can't really help. Like you, my perception from reading here is that the optispark is less than, well... "optimum".

Thanks.
I've ran these turds for many years. The oem optis can be reliable provided they stay sealed and the ventilation system is in working order. The biggest problem with the design is that they are tucked under the water pump (damp and hot) and the distributor cap is a "correct a cap" design, so some of the high voltage traces cross paths. Along the way they pass directly over the optical sensor, which is also bad. My hope was that by removing the high voltage off of the cap and running the gen 3 coil near plug setup I could still retain the cam/crank signal.
I would be curious to know how many lt1 guys still run the opti with MS and if they DON'T have this issue.
I've got a few things I'm going to try in an attempt to salvage this setup (reroute the plug wires, wrap the opti wiring harness in shielding) and if the issue still remains I'm pulling the trigger on a 24x signal kit

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[firebird_1995]

Is there a way to see what cylinder is being fired in a datalog? I moved my spark plug wires around and the issue seems to have gotten worse. Maybe if I could narrow down what coil is being fired I could find a pattern

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[billr]

Maybe you could see it in "timing error" or "rpmdot"?

If you try it, be sure to set the max/min limits for the data field to make variations show better. If scaling is left to "auto" the severe spikes (lost sync?) will mask what you are looking for; rpm variation from just one cylinder not firing.

[firebird_1995]

I was hoping that somewhere in the program you could overlay ignition events over a datalog. I set up 8 custom events triggered off of spark a-h and am going to datalog today to see if I can see some sort of pattern. I don't think the datalog will have high enough resolution to catch exactly what cylinder the misfire is happening on but it's worth a shot.
Off topic, I seen in another post that you are 24x. I use ckp for crank and digital high frequency for the cam sensor, if I swap to a 24x trigger could I retain the DHF for the cam signal? I'm using my CMP for VSS

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[jsmcortina]

Is there a way to see what cylinder is being fired in a datalog?

This won't show up in a regular datalog.

You can use the High Speed "Engine logger", to see some events but it is difficult to interpret too. The only real way would be with a 9 channel recording logic analyser I think?

James

[firebird_1995]

Currently, the shielded wiring for the optispark ends under the coil packs on the passenger side then extends to a non shielded oe pigtail down to the opti. I'm going to extend the low res signal wire today and see if it helps

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[firebird_1995]

Shielded wire didn't make a difference. Looking through some composite logs I've seen a lot of errors on the high res signal. I'm unsure of the exact rpm it occurs but it's over the 1k rpm mark that I've read the pcm isn't looking for the signal, if I understand correctly. I did have on odd wave on the low res signal but no sync error reported.
I'm going to try putting a new opti on and see if there's any change.

[firebird_1995]

As an update, I pulled the optispark off to swap over to crank trigger. When I got it apart, I found that that rotor screws were loose and about 3 turns from falling out. This isn't an uncommon issue with these units but on a stock pcm it will usually start throwing a dtc prior to coming completely apart. If you look close you can see the trigger wheel has a lot of slop between the alignment pins. I had used this distributor for about a year on a carbed setup to supply an rpm signal to shift a transmission, so I wouldn't have noticed any issue then. I probably could have put a new opti in but with running an aftermarket ecm there was really no reason to stick with it. I just don't have the patience to deal with them anymore.


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