High RPM misfire? random
03-19-2010, 11:37 PM
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High RPM misfire? random This is such a pain... is this because of the dreaded opti or a weak coil?
sometimes, high RPMS (over 4 grand or 5 grand) you can feel the car like its misfiring. its RANDOM. sometimes when I get on it, its PERFECTLY smooth. othertimes, like tonight racing a 350z, it did it top end of 2nd and 3rd. i still beat him btw. but like, WTF? its not all the time
sometimes, high RPMS (over 4 grand or 5 grand) you can feel the car like its misfiring. its RANDOM. sometimes when I get on it, its PERFECTLY smooth. othertimes, like tonight racing a 350z, it did it top end of 2nd and 3rd. i still beat him btw. but like, WTF? its not all the time
03-19-2010, 11:52 PM
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Not to hijack your thread, but my buddies lt1 just started this a few days ago. Like you said its completely random. The car will break up for a split second or so then act just fine.. 
After this happens it smells like it was running really rich.
After this happens it smells like it was running really rich. 
03-20-2010, 12:02 AM
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never. ha. when I got the car 4 years ago or so, it has MSD wires i assume (red wires). Its probably due, but its just so lame that its RANDOM. not everytime, sometimes. 
haha.
haha.
03-20-2010, 12:09 AM
#5
go outside when its dark and while the engine is running make sure none of your plug wires are arching....
Prob would be a good idea to due a tune up regardless since its been so long
Plugs
Wires
Fuel Filter
ICM cooling mod...
do you have anyone local you can switch coils with to see if that fixes your prob?
Prob would be a good idea to due a tune up regardless since its been so long
Plugs
Wires
Fuel Filter
ICM cooling mod...
do you have anyone local you can switch coils with to see if that fixes your prob?
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06-05-2011, 11:25 PM
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Same problem here, I just did the icm cooling mod... whats next 160,000 miles on the clock, new plugs and wires 60k miles ago. I'm thinking fuel pump, fuel filter changed 30k miles ago - rusty as hell on the outside. I guess i need to confirm fuel pressure with a gauge - I will say this original vented opti.
Weak coil? Bad icm? Bad fuel pump? or Bad opti?
Weak coil? Bad icm? Bad fuel pump? or Bad opti?
06-06-2011, 12:35 AM
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Been battling my 52-5400rpm hiccup for over 2 months now. Ive done countless searches but no one posts up what cured their problems.
I say, as long as the car starts and drives fine and doesn't guzzle gas, do the little things first and work your way down the list.
1) Inspect wires and plugs, if its been a couple years replace anyway
2) Fuel Filter never seems to be a culprit, but its cheap and it 'could' be clogged
3) Check Fuel pressure
4) Ohm injectors
5) replace coil
6) ICM <---seems to be a culprit sometimes, but its more of a ignition starter
7) MAF <---unhook see if it runs smoother on speed density
8) OPTI <---this part sucks, this isn't a clean job, you have to remove it to inspect it and hopefully the screws fell out and you can put them back in after you clean up the inside, or just replace it as its the last peice to the puzzle.
9) Push car off a cliff if it still happens. Im only on step 2 and Im already thinking of step 9.
I say, as long as the car starts and drives fine and doesn't guzzle gas, do the little things first and work your way down the list.
1) Inspect wires and plugs, if its been a couple years replace anyway
2) Fuel Filter never seems to be a culprit, but its cheap and it 'could' be clogged
3) Check Fuel pressure
4) Ohm injectors
5) replace coil
6) ICM <---seems to be a culprit sometimes, but its more of a ignition starter
7) MAF <---unhook see if it runs smoother on speed density
8) OPTI <---this part sucks, this isn't a clean job, you have to remove it to inspect it and hopefully the screws fell out and you can put them back in after you clean up the inside, or just replace it as its the last peice to the puzzle.
9) Push car off a cliff if it still happens. Im only on step 2 and Im already thinking of step 9.
09-05-2012, 11:41 PM
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09-06-2012, 03:43 AM
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I was having the same issue a couple years ago. I'd replaced everything I could think of in the ignition and while I was tinkering around on the dyno, I got the car to miss and noticed it lost ~115hp in a split second and then came right back. Running out of ideas I replaced the crank position sensor and the car hasn't done it again in a little over a year. Maybe false crank walk
09-06-2012, 08:18 AM
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I ended up changing the fuel pump with a walbro 255lph kit I pieced together and the problem was fixed. (This was after checking all plugs, wires, new ignition coil and new optispark). I put a new ICM on there and did the cooling mod for the hell of it too). Check your fuel pressure - mine was leaning out at high rpm meaning the pump could not keep up with the demand. Also check your fuel pressure regulator there should be no fuel or fuel smell on the vacuum tube.
