Missfire on Nitrous, Help me chase down the gremlin!
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From: San Rafael, CA
Missfire on Nitrous, Help me chase down the gremlin! Ok, at first the car ran fine. I left the dyno with 470/550 at the wheels. And was very happy. Later I noticed a miss at idle and fixed the problem
with new 02 sensors and a slightly different tune. Changed the plugs and wires just for the hell of it. Plugs are gapped at .038. I'm spraying a NOS 5177 kit with no jets. It gave me about 130/200 at the wheels. Well last Sat I took the car to the track and misfiring it ran a 11.73 at 124.5. Now the car runs absolutly perfect NA. No miss, no bucking, stuttering or any of the such and traps between 112-114 NA. The wires are brand new. They are all seated, all the plugs are tight and the AFR is fine NA and on spray. It's not the MAF. EFIlive and AutoTap show no problems. Tried spraying with only one of the 2 lines hooked up to the intake for a smaller shot, and same result. The only thing I can think of is a week coil, so I got 8 used coils off of an LS1 with 40K on it. Those should be fine. I will switch them out tommorow and see if the problem goes away. Does anyone else have any suggestions of what it might be. I don't think it's a vacume leak, sprayed a can of breakclean all over the engine bay with no effect on idle. No codes eather. Ideas guys, similar problems and fixes. Any help or input is gratly appriciated.
p.s fuel pressure is fairly steary at 58-55. Thought it might be my FPSS. Bypassed it same result. Tried MAF from other LS1 same result. Thought I might have too little timing on spray gave it more and again same result. Leaning the car out or richining it up has no effect.
with new 02 sensors and a slightly different tune. Changed the plugs and wires just for the hell of it. Plugs are gapped at .038. I'm spraying a NOS 5177 kit with no jets. It gave me about 130/200 at the wheels. Well last Sat I took the car to the track and misfiring it ran a 11.73 at 124.5. Now the car runs absolutly perfect NA. No miss, no bucking, stuttering or any of the such and traps between 112-114 NA. The wires are brand new. They are all seated, all the plugs are tight and the AFR is fine NA and on spray. It's not the MAF. EFIlive and AutoTap show no problems. Tried spraying with only one of the 2 lines hooked up to the intake for a smaller shot, and same result. The only thing I can think of is a week coil, so I got 8 used coils off of an LS1 with 40K on it. Those should be fine. I will switch them out tommorow and see if the problem goes away. Does anyone else have any suggestions of what it might be. I don't think it's a vacume leak, sprayed a can of breakclean all over the engine bay with no effect on idle. No codes eather. Ideas guys, similar problems and fixes. Any help or input is gratly appriciated.
p.s fuel pressure is fairly steary at 58-55. Thought it might be my FPSS. Bypassed it same result. Tried MAF from other LS1 same result. Thought I might have too little timing on spray gave it more and again same result. Leaning the car out or richining it up has no effect.
Last edited by ricekillman; Jan 20, 2005 at 03:46 PM.
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From: San Rafael, CA
Originally Posted by Nitro Dave's Nitrous Outlet
What spark plugs are you running? What are they gaped at/ and have you checked them.
Dave
Dave
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Originally Posted by Nitro Dave's Nitrous Outlet
I dont think the gap is the problem.I normally gap them around 36.Are you sure none of the plugs are cracked.Ill put some more thought into this..
Dave
Dave
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Plugs that are cracked can run really good on motor and suck on bottle. This has happened to me more then one time. NGK plugs are not the best plug at any rate. I use them but they seem to not last and I have had cases where new plugs are even bad. I would put a new set of plugs in it. I don't think the coil would have anything to do with it. You are working that coil pack just as hard on motor as you are on the bottle, so it would show in either run. I know the only reason my car has ever acted up on the bottle is when there is a plug issue. JMO
with the engine cold, start it up and idle. take a water bottle sprayer and with water spray down all the plugs wires and coils at night. Looks for a spark, if there is anything at all you will see it! Any spark issue will show up, I have found many plug wires shorting to headers this way. I know we do not have long wires but with the headers it makes it tight. Just and FYI simple check 
Dan
Dan
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Thread Starter
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Well, I changed all the coils for ones off of a 40K car and still the same problem. I guess I will have to chage the plugs yet again and go over everything. Will keep you posted. The only other thing that I think it might be if it's not the plugs is a weak spring, rocker or somthing along those lines, but I would think that it would show up NA as well.
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Thread Starter
On The Tree
Joined: Feb 2004
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From: San Rafael, CA
Well we do have the crappy 91 premium here in California, but I got gas a couple of times scence the problem occured and all the same result. I don't think it's the gas Been through 3 half full tanks. What's weird, is there is no detonation and hardly any knock. It's like the mixture is just not igniting. Shoot I'm becoming an expert on changing plugs on this thing. Tommorow I will put in a brand new set. Just to make sure there isn't a minor crack or something. Maybe I got a bad set. Worse things have happened. If it's not the plugs. It would almoast have to be somthing with the valvetrain, but wouldn't a valve/rocker/pushrod/spring failure or weakness show up NA as well. At least a the higher RPM range. What is happening here is as soon as the N2O hits at 3K it revs fine but through a series of misses. Sometimes as few as 3 others to as many 10 or more though each gear. I spent all day on the dyno with this and the AFR looks perfect.
Last edited by ricekillman; Jan 22, 2005 at 11:26 AM.
Is the misfire in all cylinders or just a couple.As far as bad gas it might take a while before that could work out of the system incuding the gas station.I would try a diffrent station or you could try octane boost or pull some timing out at 3000rpm to werever your shift point is.I run ngk 8 and gap them at 28 and don't have a problem but i run 104 octane.
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From: San Rafael, CA
I am pulling timing as soon as the car sees nitrous. Also the miss is not in one cylender, but I really don't trust EFIlive/AutoTap with that. There have been numerous times where the cylinder in question has been the later one in the firing order or the other way around.
Thread Starter
On The Tree
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From: San Rafael, CA
Originally Posted by tuff
I take it your running a timing tuner.On a tap is it showing your timing being pulled when on the bottle.Just want to make sure timing is coming out of the motor. 
Thread Starter
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From: San Rafael, CA
A scanner? The car has been scaned more then Straship Enterprise there is nothing to figure out.
I FIXED IT YEAHHHHHH!!!!!!!!
Pulled the injectors, pulled the rails, the intake and the valve covers to see if there was anything wrong. Just like I expected nothing was wrong. Put the car back together. Reseated the injectors to make sure it wasn't them and checked the o rings. Everything looked cool. Pulled the plugs yet again (so easy now with no EGR AC or Air) checked every one all looked great. No fauling no cracks all looked thesame and good. Put a new set of TR5s at .035 in there and miss is gone. I don't know what fixed it. I know for a fact that it wasn't the wires or seating cuz I made sure those things were on there like 10 times. Is it possible NGK made weak plugs. Is there such a thing. Shoot maybe it wasn't the plugs at all. I don't know. All i know it's fixed. Shure would be nice to know what fixed it though. Ohh well.
I FIXED IT YEAHHHHHH!!!!!!!!
Pulled the injectors, pulled the rails, the intake and the valve covers to see if there was anything wrong. Just like I expected nothing was wrong. Put the car back together. Reseated the injectors to make sure it wasn't them and checked the o rings. Everything looked cool. Pulled the plugs yet again (so easy now with no EGR AC or Air) checked every one all looked great. No fauling no cracks all looked thesame and good. Put a new set of TR5s at .035 in there and miss is gone. I don't know what fixed it. I know for a fact that it wasn't the wires or seating cuz I made sure those things were on there like 10 times. Is it possible NGK made weak plugs. Is there such a thing. Shoot maybe it wasn't the plugs at all. I don't know. All i know it's fixed. Shure would be nice to know what fixed it though. Ohh well.