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Old 10-09-2008, 04:32 PM   #1
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Default Plug gap and MS resets

I had some time to kill today so I went for a random datalogging drive.

Three times, when I accelerated from zero directly into boost, I got resets! And that's with a .025 gap on new-ish plugs, new-ish 8.5mm wires, and working-but-generally-suck-*** stock coils.

I have an unopened set of FM's extra-long plugs. My idea is to try those with a .020 gap.

Thoughts?

(Please keep any technical feedback on the simple side. I'm still a lowly student of Prof. Paul and genuinely trying to expand my comprehension of MS fundamentals, without getting over my head or breaking anything - this car is my DD.)
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Old 10-09-2008, 05:28 PM   #2
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Two questions:

1- What makes you think that plug gap is causing this?

2- Are these in fact processor resets (marked by a red line in the log) or just misfire events? A processor reset, when it happens, is a fairly violent event.

Let's see the log.
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Old 10-09-2008, 06:00 PM   #3
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EK, check your boost cut off settings.
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Old 10-09-2008, 09:10 PM   #4
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Log is attached.

When Paul initially installed the MS a few months ago, we had the same problem. We were using a gap of .03x and we kept getting resets under boost which (I think) he said were caused by spark plug "blow-by" (is that the correct term?) .... eventually we lowered the gap to .025 thanks to suggestions found here on MT and all was well. So, since I was in the car when those resets happened the first time, I recognized the same reset tonight. When I opened the log in MLV, sure enough, there were red marks and 3 resets listed. Artie -- no, it wasn't boost cut; this happened at around 8 or 9 psi if I recall correctly. My boost cut is much higher than that.

Last night I was searching around the forum and saw that some folks use a gap as low as .020, so that's how I got this idea today.

I don't know if using the longer plugs has any impact on the required gap.
Attached Files
File Type: xls datalog200810091432.xls (857.4 KB, 71 views)
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Old 10-10-2008, 02:41 AM   #5
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Yep, those are definitely bona-fide resets- you can see the barometer go apeshit when it happens. Under "More Settings" go to "Barometric Correction" and set the Min to 90 and Max to 100.

As to the root cause... There's certainly no harm in your gapping the plugs down a bit, I'm just having a hard time imagining how plug gap is causing your problems unless there's something else very wrong with your ignition system- insulation missing from wires, degraded coil windings causing an internal arcover from secondary to primary, that sort of thing.

Is your MS set to activate any external solenoids or relays when in boost? EBC for instance, or some other custom gizmo? WI?
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Old 10-10-2008, 03:00 AM   #6
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Quote:
Originally Posted by Joe Perez View Post
Under "More Settings" go to "Barometric Correction" and set the Min to 90 and Max to 100.
Will do ... hey, I checked just now, it's already at min 95 and max 105 ... pretty close to what you suggested (and presumably what Paul put in) ... hmmm....

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Is your MS set to activate any external solenoids or relays when in boost? EBC for instance, or some other custom gizmo? WI?
Yes, there is a GM boost solenoid.
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Old 10-10-2008, 11:52 AM   #7
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Quote:
Originally Posted by evank View Post
Will do ... hey, I checked just now, it's already at min 95 and max 105 ... pretty close to what you suggested (and presumably what Paul put in)
Not sure I can explain that. Looking at the log you posted, baro starts at 100, then after the first reset at 226.500 it goes to 155 (which is about what MAP was at the time) and then at 228.480 on the second reset it goes to 116.


Quote:
Yes, there is a GM boost solenoid.
I'm just trying to think of things that could be creating electrical noise within the MS, a common cause of processor resets. Do we have the flyback diode installed across the EBC solenoid?
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Old 10-10-2008, 03:37 PM   #8
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The unit was built by DIY so I imagine they did if it should be there.
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Old 10-10-2008, 05:07 PM   #9
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No, I'm talking about an external diode 1N400x), placed across the two terminals of the EBC solenoid in a reverse-biased configuration. IOW, the striped end connected to the +12v lead, and the other end connected to the lead which connects to the MS.

Give it a shot and see if it has any effect.
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Old 10-10-2008, 05:26 PM   #10
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Probably wrong, but...

It could be noise from the ignition system interfering with it. I'm running EDIS on my 99' and I made some fancy MSD low ohm sparkplug wires. Well, I've had an undiagnosable miss the entire time. Replacing the ignition system (except for the sparkplug wires) doesn't fix it. I have noise like crazy and it gets worse with RPM (imagine that...). I'm 99% sure it's the low ohm wires causing the problem. I don't suppose you're running low ohm wires or Champion plugs are you?


EDIT: And you'r point???? My point was I get resets too. And I get crazy *** numbers in datalogs on almost every sensor sometimes. Moving grounds around moves the problems around, but it never fixes it. Seperating every ground helped the most. Then I put them all on a ground bar like what you would see in a breaker box. I have noise bad. I even added ground and cleaned ground and tried my damnedest to avoid ground loops. It's gotta be the ignition wires.

Last edited by patsmx5; 10-10-2008 at 05:44 PM.
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Old 10-10-2008, 07:27 PM   #11
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Quote:
Originally Posted by Joe Perez View Post
No, I'm talking about an external diode 1N400x), placed across the two terminals of the EBC solenoid in a reverse-biased configuration. IOW, the striped end connected to the +12v lead, and the other end connected to the lead which connects to the MS.

Give it a shot and see if it has any effect.

OK. will try that.
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Old 10-10-2008, 08:41 PM   #12
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It better NOT be the frigging spark plug wires. I spent $83.95 + s/h on FM's Magnecor 8.5-mm wires because they're supposed to be good.
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Old 10-10-2008, 11:15 PM   #13
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Are you getting the resets consistently now or are they just a fluke? If consistently happenening at 8-9psi I suggest unplugging the boost control solenoid to see if that solves the problem. You can build that much boost without it, right? Remember when we first were having the issue I suspected that damn thing but abandoned the idea after the regapping seemingly solved the issue.
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Old 10-11-2008, 12:35 AM   #14
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Fluke.

I didn't have ANY resets since we changed the gap to .025. Then, 3 in one trip. None since.

If the solenoid is the problem, what's the solution? Some other brand of solenoid? Or a more traditional EBC?

Does any of this affect the big problem I'm having with engine misfires? Remember I had THAT problem BEFORE we put in the megasquirt ......
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Old 10-11-2008, 12:41 AM   #15
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Quote:
Originally Posted by evank View Post
Fluke.

I didn't have ANY resets since we changed the gap to .025. Then, 3 in one trip. None since.

If the solenoid is the problem, what's the solution? Some other brand of solenoid? Or a more traditional EBC?

Does any of this affect the big problem I'm having with engine misfires? Remember I had THAT problem BEFORE we put in the megasquirt ......
Did you have the misfires with those sparkplug wires before MS? If so, I suggest getting a new set of stock wires and seeing if that helps. I can't wait to get rid of my ignition miss... Sucks. I'm looking for COPs.
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Old 10-11-2008, 01:44 AM   #16
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Quote:
Originally Posted by patsmx5 View Post
Did you have the misfires with those sparkplug wires before MS? If so, I suggest getting a new set of stock wires and seeing if that helps. I can't wait to get rid of my ignition miss... Sucks. I'm looking for COPs.
Actually, the Magnecor wires, new plugs, and new coils were some of the things we tried pre-Megasquirt to get rid the misfires in the first place! Then we thought the misfires were fixed (by replacing the injectors), so we went ahead and 'squirted....

Background: the misfires first started several months before I even considered 'squirting. Came out of a bar one night, started my car (stock ECU, 305 cc injectors), and there was a loud, scary-sounding metallic crunching noise, then my CEL started blinking and the car ran very bad. LOL, no I didn't throw a rod or anything. Stupidly, I limped the car home. Paul figured out that I had an injector go bad and the car was running on 3 cylinders. So we replaced the bad one and all seemed well. A month or two later, the roughness returned. That's when new plugs / wires / coils didn't solve the problem, so we put in a whole different set of injectors (I think 265s or something), instead of just replacing the one possibly bad injector. After that all seemed well again. Then a while later still, I bought the Megasquirt, and we replaced the 265s (or whatever) with 460s. For almost all of the time since then, I haven't NOT had a CEL for misfires. Oddly, in real life, the car runs pretty well as my daily commuter! But it does seem to vibrate a lot.

I have a nagging feeling that something other than an injector went awry in the bar parking lot that night. What it was, I don't know.

Paul: remember when we put in the 460s, we saw a small part broken on the fuel rail .... was that significant?
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Old 10-11-2008, 09:38 AM   #17
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To answer your question about a solenoid solution Joe gave a possible solution, a diode across the terminals.


Small broken part on the fuel rail? I don't recall that at all unless you are referring to a plastic wire bundle thing.

In my defense Evan never told me about the "loud, scary-sounding metallic crunching noise," until about about a week ago.
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Old 10-12-2008, 10:18 PM   #18
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Installed the diode today. $1.06 for the package of diodes from RadioSuck. Took less than 5 minutes, going slowly and carefully. Will keep an eye on it.
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Old 10-12-2008, 11:33 PM   #19
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.1uf cap on js8?
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Old 10-12-2008, 11:44 PM   #20
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Quote:
Originally Posted by Braineack View Post
.1uf cap on js8?
JS8? Huh? Isn't that something on the Megasquirt circuit board?

I was talking about a diode that sends current from the EBC solenoid's output wire back to the input wire, as superbly explained (above) by J.P.
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