Fluctuating idle and other issues
04-26-2017, 12:00 AM
#1
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Join Date: Jun 2011
Location: Corpus Christi, TX
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Fluctuating idle and other issues
I managed to borrow a Snap-On Solus Edge in an attempt to trouble shoot my car. the car is a 96 SS with an LT-4 motor. 1st issue: the Solus thinks my car is a '96 Caprice with a 4.3 liter, V-8 engine. And the serial number does not match the car. Weird. I took the car for a drive with the Solus hooked up but I can't find a file with today's date so I don't know if it recorded anything. But for the entire 20 minute drive the Solus display said the car was in open loop. Usually after that long of a drive the idle would start to fluctuate and would occasionally rev to 1600 rpm. But this time it wasn't doing that. I went into a store came out and now got the fluctuating idle and the Solus said it was in closed loop. I had played with the Solus once before and forcing it into closed loop seemed to settle the idle down. Any advice would be appreciated.
04-26-2017, 04:12 PM
#2
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Re: Fluctuating idle and other issues
Does the Solus ask you to select the engine code, or does it pull it out of the VIN in the PCM?
What brand Opti do you have? I have uncovered at least a 1/2-dozen erratic idle problems caused by RPM spikes in the data stream from the MSD optical cam position sensor. For a single frame of data, an irrational RPM value appears, sometimes as high as 7,000+ RPM. The PCM responds by jacking up the IAC counts. Another spike, and another, and the IAC drifts up to 160 raising the idle, and then in between irrational counts, the PCM pulls the IAC counts down to try and control the idle, so the idle is drifting up and down.
The problem is so predominant in MSD units bought over the past year or so that people other than myself are now detecting the problem, so it's really an epidemic. Dealing with MSD Engineering, I sent them data logs from two different cases, they asked for the unit back from one of the vehicles. They got it, reviewed the analysis in the logs and the unit and feel they came up with a "fix". They've returned the Opti to the owner to reinstall, to see if it cures the problem (he already cured it by buying a cheapo Opti - so I don't know when he will install the "fixed" unit.
What brand Opti do you have? I have uncovered at least a 1/2-dozen erratic idle problems caused by RPM spikes in the data stream from the MSD optical cam position sensor. For a single frame of data, an irrational RPM value appears, sometimes as high as 7,000+ RPM. The PCM responds by jacking up the IAC counts. Another spike, and another, and the IAC drifts up to 160 raising the idle, and then in between irrational counts, the PCM pulls the IAC counts down to try and control the idle, so the idle is drifting up and down.
The problem is so predominant in MSD units bought over the past year or so that people other than myself are now detecting the problem, so it's really an epidemic. Dealing with MSD Engineering, I sent them data logs from two different cases, they asked for the unit back from one of the vehicles. They got it, reviewed the analysis in the logs and the unit and feel they came up with a "fix". They've returned the Opti to the owner to reinstall, to see if it cures the problem (he already cured it by buying a cheapo Opti - so I don't know when he will install the "fixed" unit.
05-02-2017, 08:40 AM
#3
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Re: Fluctuating idle and other issues
Sorry I missed this post and haven't responded earlier.
The Solus is retrieving the information. I am not selecting the engine code.
Unfortunately, I do have an MSD Optispark. I had an MSD in another car for years and it was awesome. That car never ran better. Not so much with this car. I bought a new MSD for this build. It was in the car, maybe a year. I can't remember exactly. But it failed due to the gasket not being installed correctly at MSD. Up to the point when it failed, I never had any of the erratic idle issues. When it failed, I returned it to MSD and they fixed it. I have had the idle issues since it came back from repair at MSD.
The Solus is retrieving the information. I am not selecting the engine code.
Unfortunately, I do have an MSD Optispark. I had an MSD in another car for years and it was awesome. That car never ran better. Not so much with this car. I bought a new MSD for this build. It was in the car, maybe a year. I can't remember exactly. But it failed due to the gasket not being installed correctly at MSD. Up to the point when it failed, I never had any of the erratic idle issues. When it failed, I returned it to MSD and they fixed it. I have had the idle issues since it came back from repair at MSD.
05-02-2017, 08:52 PM
#5
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Re: Fluctuating idle and other issues
I have no idea. I bought the car a couple of years ago. It had obviously been raced in it's past life. The motor was blown when I bought it. I did send it off to PCM'sforless to have it remapped after installing the LT-4. I would have thought they would have sent back the same PCM I sent them.