yes, and to add to that why is it intermittent?

 

Fred

read the thread from beginning.

a guess is he "may" have a short/bad connection somewhere in his wiring.

Op's note about the "new improved MSD Opti"...my only experience with the MSD opti (assume it was an older "model") was not good and caused high RPM miss until I replaced it with my old AC Delco....it did not produce the IAC count issue OP has and "high idle"

 

I've read the whole thread from the beginning... in fact, I've put a large amount of time into trying to help him and providing responses.

What part do you feel I have missed?

 

To clarify. MSD redesigned their opti's at the end of last year. I have the latest version. I have yet heard of a bad one but I guess mine could be. I am currently leaning in that direction. From what I gathered, the low res. side of the opti sends data to the computer and that is what the computer uses to set the IAC #'s. So I may send it in for warranty replacement. Although I didnt get any dtc's.
Fred your assistance is much appreciated, count on that.

I have tried to send you my latest data log by email. It is to large to do anything else with it. All I could think of was a copy/paste, I hope you get it. there is some weird spark retarding going on but the knock counts dont change. I dunno, thats new

 

You can't send the data as part of the text of the e-mail. There is no way for me to reconfigure it in the correct columns, or manipulate the data. You have to attached a file in .csv format to the e-mail, or upload the .csv file to an FTP website.

 

ok, I'll try that

 

Fred

you certainly have tried to help the OP. Data log interpretation is above my pay grade.

I do know that parts, mechanical & electrical issues can result in errant data as the "physical" problem (be part failure, install error, bad electrical connection, etc) is often hard to pinpoint.

I have had my tuner assist me (by internet/phone) in finding wtf was causing a particular issue.....it was ALWAYS some part of the car that was bad causing the "problem"...not the tune. The data logging did however assist my tuner in directing me towards a particular part to check.

Op has a "MSD" opti...on the surface that raises a flag but as he states it is the new & improved one but I don't know what the "improved" part of a new MSD opti is. My experience with MSD Opti, and others, was either complete failure or high RPM miss. Op's high idle/IAC issue is not something I have heard as a Opti problem...but again I don't know if a opti of any brand can cause that.

 

I guess what confused me is why you felt it necessary to tell me:

..... when it should have been obvious I had read it from the beginning.

 

I have the data log and it's in the correct format. The first thing I notice is that the "fuel trim enabled" flag is not set ( = 0 ), and that prevents the PCM from adjusting the long term fuel trims in response to O2 sensor feedback, even though the flag for "closed loop" is set ( = 1 ). And it's not because the "power enrichment" flag is set ( = 0 ), because for most of the log it's not in PE mode.

Also notice the target idle speed is 675 RPM. Has this PCM be reprogrammed?

I'll focus on the erratic idle, but it's going to take a bit longer.

 

I am basing the opti possibly being the problem based on what a Tech at MSD told me when I called them to discuss this situation with them. He explained to me the pcm uses the low res. side of the opti to base its iac# on. but Im not real sure about that either. he didnt sound real knowledgeable.

Ill give you the whole history so its all out on the table.
I bought the car in July last year. It immediately had a starter go out. The new starter I purchased was also non functional but I didnt know that, So all the grounds and cables were cleaned and replaced as needed at that time. I found out the starter was no good so I swapped in a new one and Im driving again. Super.
Sept, the car started to just shut off on me, for no apparent reason. When it would do this it would sometimes fire right back up, other times I would have to wait. The only other symptom was spark knock under heavy acceleration. I couldnt diagnose it because it was intermittent. One afternoon while on the E-way it shut off like someone turned the ignition off. Started itself back up like nothing happened. a few miles later it shut down again. This time it took an hour to restart. I took it home . While driving it home it was hitching a bit here and there. but it made it all the way without quiting.
So,it was the end of the season. I had a couple of lifters that were louder than I liked. and plans for some long tube headers. I began to tear it down, hoping I could figure out what was what along the way. And I did. The ebay opti, that was on it had spit out a rotor screw that was allowing the rotor to pivot on the remaining screw and chew itself up on the cap. Not to mention the screw floating around inside the optic section.
So, I installed new head gaskets because I was there, new roller lifters, stainless headers and a Y-pipe, new plugs, wires. Fixed up a lot of clutter, some substandard repairs , deleted the egr and airpump. Put it all back together, only to have the worlds worst running lt1.
I had started with a Rich Porter opti. But the car shook like a paint shaker at around 1800 RPM'S. New motor and trans urethane mounts were installed with the headers. So I replaced the wires, no effect. I checked the injectors by moving them around, no effect. I had the icm checked and rechecked, and finally replaced it anyways with a know good unit. No effect. I replaced the coil. No effect. I also reset the lifters no less than 4 times thinking maybe a valve wasnt closing, but it didnt help. Finally in desparation I replaced the Rich Porter Optispark with an MSD unit. NADA.
After a lot of thought and frustration I had a suspicion about what it might possibly be. So I took it to a local shop that does a bit of speed work. gave them a list of what was done to the car, and said call me when they knew what it was.
The finding was , Bad converter. Revmaxx. Unbolted the car ran silky smooth. I replaced the converter with a Precision New Hampton 3000 stall and it been great, except for this intermittent IAC problem.

 

Fred. Thanks for explaining how to send it, and hurray!
Yes. The previous owner did have some reprogramming done to the Pcm. I noticed it but I am just learning about some of this stuff. Do you think it needs to be re-enabled?
In park the target is 675 in drive it changes to 575. As I remember anyways.

 

Something else I noticed, why is it showing "speed" of 1 and 2 mph? its in park. Towards the end of the log.

 

The stock programming for idle is 550 RPM in gear and 650 RPM in neutral.

 

I spoke with the former owner and he confirms that there was "tuning" done to the pcm. After the tuning session the tuner promptly fell off the planet. He was never happy with the tune either. so that answers that question.

 

I should have another pcm by next week. I had already planned to purchase the drive train from another car, a buddy is doing an ls swap. So if I need to I can use the pcm from his car.
But The question remains on this one, should I enable the long term fuel trims? I have no idea why they were disabled, neither does the previous owner. Would there be a downside to enabling them?
Could this be a contributing factor in my IAC problem?