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backfires and missing scan9495 log

Old 09-11-2015, 11:55 AM
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backfires and missing scan9495 log


First time here. Recommended by GaryDoug to put my scan9495 logs here, and stated that Injuneer has a great handle on analysis of the logs produced by scan9495.

I have a 94 Formula Firebird, LT1, T56, headers, Delteq Opti-Direct ignition, SLP air intake.

Issues - misses, stumbles and backfires, mostly before warmup when throttle applied, though does occur after warmup on occasion, this is intermittent. Idles good, with minor occasional "blips".

178k miles
Found melted O2 sensor connector (poor header installation work by shop)
Both O2 sensors replaced,
MAF replaced
Optic-spark replaced 1000 miles before Delteq installed

Initial scan produced an O2 sensor loops alternating between open and closed, corrected by O2 replacements.
Had DTC's 41 and 42.
I cleared the DTC's and they have returned. Curious that I have both 41 and 42?

I was hoping someone here (Injuneer?) with a good understanding of the nuances of the logs from scan9495 could review this and let me know what you think!

But how to get the scan file to you? The forum says I cannot attach files?

Also looking for consensus on suggestions and recommendations for a good inexpensive oscilloscope to purchase for more concise troubleshooting.

Appreciate it!


Last edited by tommalcolm; 09-11-2015 at 12:01 PM.
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Old 09-11-2015, 03:02 PM
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Re: backfires and missing scan9495 log

How long have you been running the Delteq? Did the problem occur immediately after install, or recently, after running fine for a while?

I'm not a fan of the Delteq, and it can easily be the cause of your problems. And of course JC Hyde has disappeared and no longer offers tech support or replacement parts.

Don't think I've ever looked at a log from an LT1 with the Delteq. Should not be significantly different.

Since the Delteq bypasses the ICM, it would probably be normal to see DTC 41 and 42. If they are active codes, the PCM would shut down the fuel injectors. Not sure how the Delteq avoids that. Do you have a wiring diagram for the Delteq install? If so, I'd like to see it. I was once running an earlier JC Hyde design on my LT1, the Electromotive Opti-Eliminator/Super Direct Ignition. Had it's issues.

Correct, you can not attach files. You either need to upload them on an FTP site, and give me the address to download. Or I will send you my e-mail and you can send as an attachment. Check your Private Messages.

I would only consider the 'scope after not finding anything in the data logs.
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Old 09-11-2015, 03:39 PM
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Re: backfires and missing scan9495 log

Hi Fred,

Thanks for the response. Forwarding the log file to you via email this afternoon. I have the manual for the delteq, I'll also forward what it has in it. I am assuming the shop followed those instructions to install.

I had been through two previous opticsparks then my shop recommended the delteq. I didn't know any better and it didn't seem it could get any worse than the opti's. It ran super fine (no, I mean fiiiine) for about 500 miles then crapped out again. Could. Not. Believe. It.

Went through two more shops and no one has been able to make my baby run right. Finally I find the melted O2 sensor connector (which was visually hidden behind the starter and header and not throwing any codes) But that wasn't the big one apparently.

If the logs don't show anything, would love to understand how to confirm whether the delteq is the issue.

A little history...initial issues 5 years ago (I bought the car new) were under hard acceleration or powering out of corners, a sudden loss of power would occur, briefly at first, as in a switch was turned off, then immediately turned back on. Over 6 months time, the frequency increased to where it wasn't practically driveable. Fuel system has also been looked at extensively, but I don't have confidence in the analysis of any previous work at this point.


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