Causes of a misfire?

M

Mannie111

Member
Here's the deal... i have a freshly built KA24DE, crank, pistons, rods, and some machine work done on the block. it's been running great for about 1200 miles.

just the other day about 2 days ago it started misfiring. i didn't really pay attention to it for about a day hoping it would go away.
today i found out it's cylinder #2 thats misfiring. The idle changes every time i take out one of the spark plug wires except for when i take out the wire in cylinder #2.

i just changed out the spark plug in that cyl and also the wire. brand new plug and brand new wire and still misfiring.

what else could the problem be? my buddy said i might have a bad fuel pump and i'm doubting it i've never heard of a walbro going bad. it's pretty new also.

thanks for all the help guys.
 
Check cylinder #2 Injector clip makes sure the connections are proper, no opens in the wire & all that good stuff. If that checks out take an extension and tap lightly on the top of the injector in case its stuck close the tapping might open it up and solve ur problem if all else fails, remove that 1 injector and have it bench tested. May be badly clogged (doubt it) or might just need to replace.
 
disconnect injector #2 and if u get no reaction from it. then theres ur prob. if this keeps happening clean your tank and make sure u dont drive on low gas too often. youll pick up dirt causing the injector to go bad
 
honestly how does running on low gas pick up dirt??? the fuel pump is always suctioning gas from the bottom of the tank is it not??? correct me if im wrong, maybe it has a float in there, but if that was the case when you filled up the tank it would stir that shit up and get sucked in anyways. but ive never been inside a tank to see and never really understood it when people said that^
 
damn, i guess i needa check my injectors X_X.

and when you said disconnect it, you mean unplug the harness when the car is running or off? or do you mean pull out the whole injector itself?
 
^he means to disconnect the plug from the injector while the car is running, but you've already established that cyl#2 is dead, so unplugging the injector on that cylinder while the engine is running will not accomplish anything.

Do what the other guys have mentioned and you should find your problem.
 
Dont worry about the whole gas tank removal and cleaning method cause if it was the tank all 4 injectors would have the same symptoms not 1...Tap on top of the injector with the car running that way if the injector opens up u'll hear the change in the idle...If that doesnt work remove the injector w/ the vehicle off and bench test that bad boy or if u want to just replace it off rip.

NavySlideby said:
honestly how does running on low gas pick up dirt??? the fuel pump is always suctioning gas from the bottom of the tank is it not??? correct me if im wrong, maybe it has a float in there, but if that was the case when you filled up the tank it would stir that shit up and get sucked in anyways. but ive never been inside a tank to see and never really understood it when people said that^
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Lol i never found that to be true...I think thats just something our parents tell us so u dont run the car low on gas...But what u said is true its always sucking fuel from the tank so on a full tank all the shyt from the bottom would float to the top causing it to suck through the pump 1st...I thought i was the only 1 who thought that.
 
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ya lol i didnt say anything for a while cuz i didnt wanna look stupid, but honestly i cant help but question that logic lol
 
DToYsMK3 said:
Dont worry about the whole gas tank removal and cleaning method cause if it was the tank all 4 injectors would have the same symptoms not 1...Tap on top of the injector with the car running that way if the injector opens up u'll hear the change in the idle...If that doesnt work remove the injector w/ the vehicle off and bench test that bad boy or if u want to just replace it off rip.



Lol i never found that to be true...I think thats just something our parents tell us so u dont run the car low on gas...But what u said is true its always sucking fuel from the tank so on a full tank all the shyt from the bottom would float to the top causing it to suck through the pump 1st...I thought i was the only 1 who thought that.
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its very very true even more so out west. ive gotten gas from a shell station while it was filling the ground tanks and my shit sucked in mad garbage and fucked my fuel system.
 
NavySlideby said:
ya lol i didnt say anything for a while cuz i didnt wanna look stupid, but honestly i cant help but question that logic lol
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i just replaced my fuel sock and fuel filter becase i ran on low fuel they were filled wilth dirt and my car stopped misfireing and im getting way better mileage
 
SAS said:
its very very true even more so out west. ive gotten gas from a shell station while it was filling the ground tanks and my shit sucked in mad garbage and fucked my fuel system.
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idk ive honestly never experienced this, but i ran 93 in my sr hatch and now 93 or no less than mid grade in my turbo e30 because gas stations seem to be out of 93 half the time here in chicago. maybe higher octane gas has less shit in it though
 
500sx said:
i just replaced my fuel sock and fuel filter becase i ran on low fuel they were filled wilth dirt and my car stopped misfireing and im getting way better mileage
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what's a fuel sock?

and the dude who i bought the car from a couple months ago had just dropped the fuel tank and cleaned it out so i wouldn't be too worried about poop being in my tank.

gonna try the injector tapping and heading to auto parts to get a 300zx fuel filter now :bigthumbu

dnpbakon said:
my walbro blew out.
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your walbro was poop :bigthumbu

lol jk bro i loves you.
and when your walbro blew out you weren't getting fuel at all right?
mines just misfiring... meaning all the other inj are getting fuel just fine.
 
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SAS said:
its very very true even more so out west. ive gotten gas from a shell station while it was filling the ground tanks and my shit sucked in mad garbage and fucked my fuel system.
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Damn i didnt know, never experienced that in my life, i've had supras sit for years and replaced the fuel filter and was good to go stopped missing & sputtering...Never had a problem with the tank and the whole system itself...But like i said try the easy things first then move to the harder things...Work smarter not harder is my motto.
 
id bet you have a dead injector i have been explaining this shit in another thread as they increase ethonal in gas its killing your fuel system. i dont know a single person that owns a 240 with a ka that hasnt had atleast one injector die in the last year. hell i blew through 6 injectors in a month before i found a gas station that sells ethonal free gas. right now they are at 10% ethonal by 2012 they are going to 15% which means the faluire rate will jump dramaticly the idea is that as they add ethonal to gas it kills out all cars pre 2000 model year and it makes you have to buy a newer car. It all enviromental government bullshit. so get ready cause 2012 if you not running race gas no more 240s
 
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