Motor mis-fire after cold start up

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rn240sx
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Motor mis-fire after cold start up

Post by rn240sx »

Ok, after letting the motor sit overnight to cool down, i started it back up today.
It idle'd fine and smooth for about 2-3 mintues. Then the mis-fire starts up. It will mis-fire every couple of seconds and then after a while, one large mis-fire will knock the idle off wack and make the motor jump up and down from 500-1000 rpm until it drops low enough to stall out..
And it will do this all day long...

I can play with the gas pedal and sometimes it will smooth it out, sometimes is doesnt work and it just stalls out anyway...

Please tell me how this is OPEN BOV related...?? I know the symptons on open bov and and in the process of recirculating that back thru, but this mis-fire and irratic idle is somthing different...
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98 240sx KA-T Full built motor JWT ecu 60-1 turbo 10 lbs
14 Genesis Coupe 2.0T stock turbo w/Bolt ons
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Greaser
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Re: Motor mis-fire after cold start up

Post by Greaser »

rn240sx wrote:Ok, after letting the motor sit overnight to cool down, i started it back up today.
It idle'd fine and smooth for about 2-3 mintues. Then the mis-fire starts up. It will mis-fire every couple of seconds and then after a while, one large mis-fire will knock the idle off wack and make the motor jump up and down from 500-1000 rpm until it drops low enough to stall out..
And it will do this all day long...

I can play with the gas pedal and sometimes it will smooth it out, sometimes is doesnt work and it just stalls out anyway...

Please tell me how this is OPEN BOV related...?? I know the symptons on open bov and and in the process of recirculating that back thru, but this mis-fire and irratic idle is somthing different...

cover up the bov with some duct tape and see if the problem continues. that will be the quick way to find out. also bad plugs will cause a misfire. I just put in a motor in my 89 and it ran fine until i revved it. put new plugs in and its all good.

did you remove your butterfly's in the intake mani?
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Post by onefast240 »

Defiantly check the BOV for leaks. I just went through this yesterday with my car. Also check the vacuum like that runs from the intake to under the throttle body. Mine was slightly kinked and causing low and erratic idle.
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Last edited by onefast240 on Sat Mar 12, 2011 3:20 am, edited 1 time in total.
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rn240sx
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Post by rn240sx »

The ONLY vacuum lines i have on my manifold are the Brake booster, Fuel pressure regulator, BOV feed and my boost gauge feed. Thats it..!!

My recirculation adaptor for my bov will arrive here tomorrow but i dont see how that will cause backfire on idle, NOR make my idle jump between 400-1000 rpm..

My spark plugs are brand new and i used the plug wires from my spare ka motor sitting in the garage that was IN USE just under 2 months ago..
www.shopboldimpressions.com
98 240sx KA-T Full built motor JWT ecu 60-1 turbo 10 lbs
14 Genesis Coupe 2.0T stock turbo w/Bolt ons
98 Supra MKIV stock twins w/Bolt-ons
2012 Frontier V6, 4-door, 6ft bed (Daily Driver)
09 Ninja ZX-6R, Full exhaust, K&N pod filters
06 Suzuki Boulevard S40
/\ all still current 8.30.20
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Post by duncan351 »

what heat range are those spark plugs? I know what you're talking about. The idle is so horrible you can't even time your motor. Try to idle the motor up to 900-1000 RPMs. Do this by using the IACV screw. Remember, that you must put the engine in the idle adjust mode first before adjusting the IACV. You must read you manual page EC-25 in the S14 manual. If the engine doesn't respond then there is a problem with that device.

In my honest opinion however I believe this is a spark misfire problem. I had it and I was able to improve my idle but it never was perfect. I had to get an ignition box to make it like stock again. Our stock ignition isn't as good as the SRs in my opinion. There for we have to up grade our ignition system to compensate for the larger injectors. There will be some S14's that might be able to handle the 50lbs injector upgrade because ignition system is working better than ours. My cure was the stock ignition can't get the job done for this size injector. Upgrade to an MSD box.
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