What would cause spark to not advance during low load cruise

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David Claflin
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What would cause spark to not advance during low load cruise

Post by David Claflin » Wed Jun 17, 2020 7:29 pm

This is on my 86 SSP car, I converted to mass air. During light load cruise the spark stays right at 15, if I give it a little gas to go up a hill, or speed up the spark jumps up to the high 30's low 40s where it should be. I've pulled both the engine harness and the EEC harness out, pulled off all the old tape, and checked everything, didn't see any issues. I've tried three different processors, two different mass air meters, a slot meter, and a pro-m, even tried it with no chip with the pro-m, and could still feel the spark acting up. This is a car that I only drive to work, and to the track, so it's not a huge issue, WOT seems to be OK, but still aggravating it doesn't run smooth at cruise.
Any ideas what to look at to remedy this?
1990 LX/A9L/stock cobra shortblock, special cam :P , ported Holley SMII intake, ported explorer heads, accufab longtubes/ 4.88, Z-spec trans
1985 LTD LX, A9P, ported AFR165, ported Holley SMII intake, 1 3/4 longtubes, 4.10, 4R70W trans, mach 1 brakes.
1986 coupe, A3M, former FHP car, stock shortblock, ported TW heads, TFS-R intake, 1 3/4 longtubes, 3" exhaust, T5, 4.56

David Claflin
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Re: What would cause spark to not advance during low load cruise

Post by David Claflin » Wed Jun 17, 2020 7:39 pm

Here's a short datalog where you can see the spark change with throttle position.
Attachments
86SSPTW-R slotmeter Pro-Minjectordata 3 2020_Jun_17_17-36-15.csv
(25.76 KiB) Downloaded 5 times
1990 LX/A9L/stock cobra shortblock, special cam :P , ported Holley SMII intake, ported explorer heads, accufab longtubes/ 4.88, Z-spec trans
1985 LTD LX, A9P, ported AFR165, ported Holley SMII intake, 1 3/4 longtubes, 4.10, 4R70W trans, mach 1 brakes.
1986 coupe, A3M, former FHP car, stock shortblock, ported TW heads, TFS-R intake, 1 3/4 longtubes, 3" exhaust, T5, 4.56

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cgrey8
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Re: What would cause spark to not advance during low load cruise

Post by cgrey8 » Thu Jun 18, 2020 5:50 am

I'm going to guess that the tune is wrongfully interpreting light-cruise as idle and thus it's using the idle spark functions instead of the spark table(s). It could also be a faulty TPS not sending a clean signal to the EEC to let it know that you are at cruising loads?

It might help to post your tune.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

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David Claflin
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Re: What would cause spark to not advance during low load cruise

Post by David Claflin » Thu Jun 18, 2020 5:24 pm

That's what I was wondering, I know the throttle body is big for this set up, 90MM, so not much throttle movement to do light cruise, but hadn't seen a way to remedy that in the tune, aside from putting a smaller throttle body on it.
I might try that just to see if it makes a difference. Here's the tune, appreciate any pointers you might have.
Attachments
86SSPTW-R slotmeter Pro-Minjectordata 3.BIN
(56 KiB) Downloaded 7 times
1990 LX/A9L/stock cobra shortblock, special cam :P , ported Holley SMII intake, ported explorer heads, accufab longtubes/ 4.88, Z-spec trans
1985 LTD LX, A9P, ported AFR165, ported Holley SMII intake, 1 3/4 longtubes, 4.10, 4R70W trans, mach 1 brakes.
1986 coupe, A3M, former FHP car, stock shortblock, ported TW heads, TFS-R intake, 1 3/4 longtubes, 3" exhaust, T5, 4.56

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cgrey8
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Re: What would cause spark to not advance during low load cruise

Post by cgrey8 » Fri Jun 19, 2020 7:17 am

That is GUFB right?
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

David Claflin
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Re: What would cause spark to not advance during low load cruise

Post by David Claflin » Fri Jun 19, 2020 4:39 pm

Yes sir!
1990 LX/A9L/stock cobra shortblock, special cam :P , ported Holley SMII intake, ported explorer heads, accufab longtubes/ 4.88, Z-spec trans
1985 LTD LX, A9P, ported AFR165, ported Holley SMII intake, 1 3/4 longtubes, 4.10, 4R70W trans, mach 1 brakes.
1986 coupe, A3M, former FHP car, stock shortblock, ported TW heads, TFS-R intake, 1 3/4 longtubes, 3" exhaust, T5, 4.56

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Paulie
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Re: What would cause spark to not advance during low load cruise

Post by Paulie » Sat Jun 20, 2020 12:54 pm

I agree you are probably using idle spark while cruising. Try increasing the idle spark multipliers (fn841n,fn841d, fn839) closer to 1 to increase spark. You might also slot your TPS and adjust it to read a little higher at closed throttle. You are at .5 volts which is quite low. While technically the EEC can adapt, I think you would be better off around .7-.8 at closed throttle.
1990 Mustang 5.0, HCI, Vortech S-trim, FRPP 42# inj., PMAS MH95, A9L, Moates Quarterhorse, BE/EA, Innovate LC-1.

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cgrey8
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Re: What would cause spark to not advance during low load cruise

Post by cgrey8 » Sat Jun 20, 2020 2:30 pm

I think ISCLPD needs to be upped when you upped NUBASE. But I don't think this would cause what you are seeing with idle spark persisting longer than you'd like on Throttle Positions near Closed Throttle.

If you've got a very large TPS installed, then I guess it's possible DELTA needs to be lowered to account for smaller movements indicating part throttle conditions.

But other than that, I'm not seeing anything obvious that would explain this.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

David Claflin
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Posts: 518
Joined: Fri Jul 07, 2006 5:23 pm

Re: What would cause spark to not advance during low load cruise

Post by David Claflin » Tue Jun 23, 2020 8:17 pm

Paulie wrote:
Sat Jun 20, 2020 12:54 pm
You might also slot your TPS and adjust it to read a little higher at closed throttle. You are at .5 volts which is quite low. While technically the EEC can adapt, I think you would be better off around .7-.8 at closed throttle.
I did this and it took care of one issue, it's advancing the spark properly now, so thank you.
I had converted to mass air because the car had an issue that cleared up after about 45 seconds of running, it would gradually get richer and richer and then it cleared up and ran normal. It did this from the first day I got the car, with a chip or not it happened. If I zeroed out the WOT fuel multiplier it was less noticeable, but still happened. I've got another '86 harness I can try because I've swapped about everything else on this.
1990 LX/A9L/stock cobra shortblock, special cam :P , ported Holley SMII intake, ported explorer heads, accufab longtubes/ 4.88, Z-spec trans
1985 LTD LX, A9P, ported AFR165, ported Holley SMII intake, 1 3/4 longtubes, 4.10, 4R70W trans, mach 1 brakes.
1986 coupe, A3M, former FHP car, stock shortblock, ported TW heads, TFS-R intake, 1 3/4 longtubes, 3" exhaust, T5, 4.56

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