i searched for misfire problems, i found a few threads and read them. it seems the most common problem was the plugs, so ill have to check those tomorrow; but i still have a question.
The car is on the GM calibration, i have an AEM Uego wideband hooked up; if its accurate its reading 10.0-10.3 under WOT, so im runnin real rich, and probably have been for a while. The car never really acted up like this before, but last night after work i was briskly accelerating after a right turn and didnt have 100% traction so it tapped the rev limiter. well anyway, after i kept going once traction returned, i thought i felt something funny. didnt think much of it. so on the way back from dinner tonight, i get on it, and after 4-4500 i notice frequent interruptions in power. i could hear the exhaust popping a little and felt the car jerk a little every time it 'cut out'. CEL started flashin after i did this a few times when i repeated this to see if it did it all the time under WOT above 4-4500, and it did in 2nd and 3rd; i slowed down at the end of 3rd.
anyway, im curious if maybe the plugs i have in there, NGK6IX-11 gapped at 052 are too large of a gap? if so that is confusing because it never did this before, but then again the cold weather could have an effect as well.
other thing i am wondering is, could the pre or post O2 sensor be plugged up? (car has 92k on it, engine[forged internals] has 7k)
or, as i read in the threads that came up, could the cat itself be plugged and somehow causing this misfiring?
if i regap these, how exactly am i supposed to do that, just push the diode to the tip and use a spark plug gapping tool?
thanks for the help, sorry if its all jumbled and doesnt make too much sense...
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
most people that are boosted run a .035 to a .028 gap .052 is bigger then stock which I think is like a .045
.35-.38 gap on mine..
as far as the problem i had similar symptoms, i switched out the coil cassette with my spare and never had a problem since..odd i know..
Built&Boosted moar
04 Cavalier Turbo r.i.p my baby
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The flashing CEL is a misfire. Your gap is way too big for boost. Gap down around .035 and see how it does.
FU Tuning
John Higgins wrote:The flashing CEL is a misfire. Your gap is way too big for boost. Gap down around .035 and see how it does.
alright will do. ill pick up that gapper thing from autozone and give it a shot.
thanks guys
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
Its also like Matt said for some reason our IDI covers like to warp a little throwing the spark off the slightest bit causing misfires happened to me about a week ago. And deffinatly change the plugs first its the cheapest thing and then work your way up.
Gap those to 35 and go from there
hmmm i guess they were gapped to .044 instead of .052 i thought they were 052 because when i bought them from sparkplugs.com they said they were pregapped to 052.. guess not. well anyway, i gapped them to 40 to start with, used the little auto zone gapper tool to check and my strut tower to lessen the gap..
weird thing though, on my way to auto zone, i did a few WOT pulls up to 6400 in 2nd and 3rd, no misfires... could have been that it was colder last night.. or my engine wasnt up to operating temp.. not sure.. i gapped them to 40 anyway and will see if i have that problem again. if so ill go down to 35. still happens i dont know what ill do lol.. spark plugs all looked fine, so ill just assume for now the gap was slightly too big. cant wait til my "HPTuners Fund" gets high enough so i can buy that and get rid of this gm calibration and its richness.. or buy that engine management thing curt posted a link to in the north central..
once again, thanks for the help guys
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
keep in mind that the weather has changed recently, and the air is ALOT COLDER AND DENCER. this means your ignition system will have to develope even more spark voltage to jump the gap. So, either close the gap and it should go away. if that does not cure it...
I have been doing some oscope work with mine recently. I noticed that the power wire feeding +12v to the IGM module is severly undersized. It like a 18 guage wire. I put my current probe on this wire, and tested when at full boost, i was getting spikes of upwards of 65amps. Also, the voltage was dropping 2 volts or more. So, i ran a separate relay and 12guage wire to it now. The voltage is rock solid, and now it can draw all the current it needs.
heres some scope shots before and after.
BEFORE
AFTER
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
Your problem does sound like gap. I think .040 is still a little big. When it is colder you usually end up with slightly more boost, which can and will blow the spark out. The smaller gap with help.
FU Tuning
alright cool, thanks for the info guys. interesting info as well nukkinfuttz, didnt know that. so what did you do with the old wire? just tape it off or did you remove it completely?
ill try the 35 gap if i have another problem once it gets even colder out.. heh. i hate winter..
thanks again
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
i cut the wire in halt at the ICM module. The side that comes from the cars harness got rerouted to trigger the new relay. Then 12 ga wire comes from that relay right back to the other part of the wire i cut that goes to the ICM. So, it sill turns on at the same time its supposed to, just with a beefier power wire.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
ahh i see, but if it connects back to the original wire, would that negate the purpose of the bigger wire?
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
well, wire has a specified resistance per foot. So, by doing what i did, i got rid of probably 10-15 feet of the smaller wire, and replaced it with about 3 to 4 feet of the much larger wire.
for instance....
if you look at the table in this link,
http://www.powerstream.com/Wire_Size.htm you can see the resistance per 1000 feet.
so, 18 ga = 6.385 ohm per 1000ft -or- .006385 ohms per foot
and can flow a max of 16 amps
12 ga = 1.588 ohm per 1000ft -or- .001588 ohms per foot
and can flow a max of 41 amps
so even though the power does eventually have to bottle neck back down where it connects back to the original wire, i have removed a large amount of restriction up to that point. wire resistance will equate to voltage drop over distances. so, my voltage right at the module is now higher, and will remain higher.
and since Power = Voltage x Current. we can see that having more voltage available right outside the ICM plug will automatically equal more Power (Watts) for the module to use.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
also, there will be a point where the little wire cannot flow anymore current. so, at that point voltage will start to be drawn down. You can see that in my posted oscope pictures.
once the wire was replaced with the 12ga, the negative going spikes have disappeared, proving that the new wire is doing what im saying its doing.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
ahh i see. very informative, thanks for the information and graphs
learn something new everyday, heh. do you think the ignition system will benefit from your mod? (reducing the chance of a misfire im assuming)
thanks again
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
of course. Its basically two transformers in there. Transformers will take whats on there primary side +12vdc and amplify that up as high as nessesary to draw a spark acrross the gap of your plug. This voltage can be upwards of 30-70 KV. I havent devised a way to measure the output yet, so we can only assume. At any rate, there will be a point with boost where the air charge in your cylendar becomes SO DENSE, that the voltage required to jump the plugs gap will not be able to develope. This will result in a misfire. Closing the gap up can allow the jump once again becuase this would require less voltage, which is what most are recommending you do in your particular situation. However, doing this will result in a less prominate "kernal" of spark energy. you really do want the widest gap as possible so this initial kernal of spark is as big as possible.
so, by making the input voltage to the primary side of the transformers higher, you are also making the output level increase by the same proportion as the ratio of turns in the transformer. so, if 12v can become 40,000 volts accross this transformer, imagine what your final output voltage could be with a supply voltage of 14.7v ! This would be a 19% gain on the primary side, so you can bet on a 19% gain on the output voltage as well. This means you can run a larger gap and not have a misfire. And a larger Gap developes a better more controlled burn.
On a side note, Jim Fueling ran a STOCK ignition system on his 700hp Quad 4. Look him up. There is no need to go swapping to MSD coils and such, the stockers are badass in there own right. Just make sure to set your system up correctly and the ignition system will do whatever you ask of it
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
AC delco Rapidfires gaped at 0.050 (GMPP recommended) with no problem.
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-----The orginal Mr.Goodwrench on the JBO since 11/99-----
A flashing MIL is a catalyst-damaging misfire. A random misfire can cause a steady CEL, I get P0300s all the time.
14.330 @ 96.37mph
