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| Missfire/bog (Page 3/4) |
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XxdjxX89
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MAY 29, 10:30 PM
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Yes , I’ve tried stalk coil , msd coil , accel coil , none of them make a difference
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XxdjxX89
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MAY 29, 11:24 PM
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So it’s night time and sure enough spark plug wires are arching,,, they are brand new msd wires so yes I don’t know where to go from here ,,,
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XxdjxX89
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MAY 29, 11:32 PM
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They are arching mid way in the wires though , any metal are the wires is near is where it arch’s ,, I’d take video but my camera won’t pick it up
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Patrick
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MAY 30, 01:39 AM
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| quote | Originally posted by XxdjxX89:
So it’s night time and sure enough spark plug wires are arching,,, they are brand new msd wires so yes I don’t know where to go from here ,,,
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I think it's normal, or at least not necessarily harmful. Not everyone agrees with me. We had a discussion about it Here. Do you still have the factory metal sleeves installed over your spark plug boots? If so, try pushing them "into" the heads so they're grounded.
Found an interesting way Here to eliminate any induced charge. It grounds the wires at the other end.
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Put stainless steel braid right over the existing wire. Leave it an inch short of both ends. At the distributor end connect all the ends of the shield wire together with an 18ga ground wire to the block. That will drain any induced current.
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[EDIT] Since it's just about midnight here, and dark , I went outside to have a look at my Formula's 2.8 running, to see if I could spot any type of arcing at all. I couldn't see any evidence of it occurring. And my spark plug wires are nothing special, although I did use dielectric grease in the boots at both ends. They were probably installed when I last changed my plugs... which might've been about six or seven years ago.[This message has been edited by Patrick (edited 05-30-2022).]
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XxdjxX89
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MAY 30, 09:42 AM
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I might give that a try , I also went with the fiberglass heat shields for wires instead ,,, I’m really hoping this arching is the cause of my misfire
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Gall757
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MAY 30, 06:35 PM
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XxdjxX89
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MAY 30, 08:28 PM
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Yes already tried 3 brand new sets of spark plugs lol
All gapped at .045
All were r42ts
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Another One
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JUN 05, 02:30 PM
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We have similar issues except the miss is a lot worse on mine.
https://www.fiero.nl/forum/Forum2/HTML/146056.html
I did get some improvement by cleaning and greasing all the grounds (each headlight, behind radio, at the ECM, battery to head, battery to frame, head to frame, harness to head). The all so important "Tan" wire to head. Technically it is the spark reference wire. Really good info at Ogres cave on the grounds.
If you figure it out please update so I know what to look at next.
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XxdjxX89
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JUN 08, 01:11 AM
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I sure will , my issue still has me baffled lol
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armos
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JUN 13, 08:06 PM
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Does it have the same misfire when it's in open loop, or only after it goes closed?
In the video it sounds like it will continuously misfire if you hold the throttle steady? Or does it clear up after a few seconds of keeping it steady?
The fuel pressure should maintain a constant reference to manifold pressure, so basically it should move in sync with what you'd see on a vacuum gauge. Is that how it moves? Otherwise injector flow rate will be inconsistent. When MAP increases, fuel pressure should increase as well, not fall off.
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At light throttle you're changing the variables, increasing the fuel demand and load but staying in closed loop with a stoich fuel mixture, so the ECM has to quickly get all the math right or it will miss. The self adjusting it can make to the fuel trims are more effective in steady state than with changing inputs.
At heavier load conditions the ECM goes into "power enrichment" (PE) which ignores the O2 sensor and targets something like 12:1 air/fuel. This makes it more forgiving.
So if there's a sensor/ECM/etc type problem, I think it's more sensitive at light throttle than heavy.
Not sure if it can go into PE in neutral though. It might, I think one of the parameters for that is RPM.
I had a frustrating misfire a long time ago caused by the ECM needing to be recalibrated for my non-stock injectors. However, in my case the light throttle miss wasn't as bad as yours, but my idle was way worse (I had a hunting idle). So if that was your issue, then I'm not sure it makes sense that your idle would still be good.
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