sustained misfire @ high boost
12-21-2008, 06:21 AM
#1
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sustained misfire @ high boost
So I'm reunited with my Miata over the holiday break, and the damn thing keeps wanting to idle around 2k and has a repeatable, sustained misfire at WOT and full boost (around 14 psi) with an accompanying difficult to describe braaaaaaappp when the misfire's occurring. Kinda like F1 traction control used to sound only muffled a bit. I've been running MLV the last few times I drove trying to iron it out to no avail really. I'm using the AFR targets outlined by Joe Perez in another thread. I just had the injectors reinspected by Witchhunter, and brother-in-law switched to platinum plugs for some reason. I also tried disconnecting the WI and that made no difference.
Setup is roughly MSPNP, Greddy 1.6, 460s.
Setup is roughly MSPNP, Greddy 1.6, 460s.
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12-21-2008, 10:58 AM
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You're on the money Pat!
I just switched out the platinums he'd installed for a new set of 7s and that did the trick! I'm stoked. No more misfire at all, it sang straight to redline. I'm glad it was just plugs because I was ready to move the logs from computer to computer to post them, take videos, etc. to try to remedy the problem.
It would be icing on the cake though if I could get this damn thing to idle lower than 2100 rpm...
I just switched out the platinums he'd installed for a new set of 7s and that did the trick! I'm stoked. No more misfire at all, it sang straight to redline. I'm glad it was just plugs because I was ready to move the logs from computer to computer to post them, take videos, etc. to try to remedy the problem.
It would be icing on the cake though if I could get this damn thing to idle lower than 2100 rpm...
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12-21-2008, 11:26 AM
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i guess it could be stuck, you might try spraying a little throttle body cleaner in the idle valve intake. Also check the TPS threshold (and that you have it set properly). You want the threshold to be activated just before the plate is closed so check and see what the ADC is at that point. I cant really think of anything else unless you messed with the closed loop settings. It really sounds like the idle is just not turning ON
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12-21-2008, 03:45 PM
#10
You're on the money Pat!
I just switched out the platinums he'd installed for a new set of 7s and that did the trick! I'm stoked. No more misfire at all, it sang straight to redline. I'm glad it was just plugs because I was ready to move the logs from computer to computer to post them, take videos, etc. to try to remedy the problem.
It would be icing on the cake though if I could get this damn thing to idle lower than 2100 rpm...
I just switched out the platinums he'd installed for a new set of 7s and that did the trick! I'm stoked. No more misfire at all, it sang straight to redline. I'm glad it was just plugs because I was ready to move the logs from computer to computer to post them, take videos, etc. to try to remedy the problem.
It would be icing on the cake though if I could get this damn thing to idle lower than 2100 rpm...
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12-21-2008, 03:53 PM
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Also, overboost is a predictive function. It can cut fuel before the limit.
The idle issue should be able to be corrected with standard troubleshooting. I'd start by looking at how much vac it's pulling and looking for a leak.
The idle issue should be able to be corrected with standard troubleshooting. I'd start by looking at how much vac it's pulling and looking for a leak.
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12-22-2008, 10:33 AM
#12
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No vacuum lines gone, everything looks to be in place. Logs show (since there's surging) MAP going from 26-39 kpa. I need to get a zip utility on the other laptop so I can post logs.
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12-22-2008, 12:01 PM
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I changed the idle over to warmup only and copied compuatic's idle settings, so now it's down to 1600 rpm and doesn't surge.
I'm pretty sure there're no leaks, but what's this starting fluid trick?
I'm pretty sure there're no leaks, but what's this starting fluid trick?
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12-22-2008, 06:17 PM
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Ok, time to eat another slice of humble pie. Bought a can of starter fluid and every time I spray near injectors 3&4 the idle droops. Seeing as the injectors were out just a few months ago it's likely them, although I suspect it could be the intake manifold gasket but I've never heard of anyone here blowing one of those that I can remember. So, tomorrow it'll be time to yank the rail and check the seals.
Last edited by kotomile; 12-22-2008 at 08:23 PM.
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12-23-2008, 07:10 PM
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Either I suck at installing injectors, or that wasn't the problem... I'm banking on the latter. Time to take a serious look at the IM gasket I guess, still getting a droop when starter fluid is sprayed by #4.
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12-24-2008, 11:19 PM
#19
same thing is happening with my car right now and it happens when i spray it on injector #4. i was thinking it might be my intake manifold gasket but i dont wanna take it off just yet. i have supra 305s and they dont flush near as good as the stocks. i was planning on putting sealant around them and seeing what happens
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