Misfire question

Nervouswreck

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After getting my engine rebuilt from top to bottom , blower ported , and a ton of other upgrades , it’s at my tuners place to get dyno tuned and four wheel alignment because i did the FTBR deal on my IRS too . Anyway , he told me i have a misfire and now I’m all paranoid . What could that be ? I have new coil packs , plugs , etc . He is busy so i don’t want to bug him but now I’m gonna be paranoid all this money i dumped into my motor build that there is something wrong . For the record my engine builder is extremely good and reputable, also the only thing i didn’t change was my injectors . They are 60 lb. injectors the previous owner put in . Any ideas ? Gonna sweat this all weekend. Thanks


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01yellercobra

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Did he say when it's missing? Is it all the time? At part throttle or WOT? Depending on when it's happening can make a difference in troubleshooting.
 

01yellercobra

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Ok. If it's at WOT it could be as simple as needing to close the plug gap a little. If it's at part throttle it'll take a little more digging. That being said I've had new plugs be bad out of the box and cause issues.
 

Nervouswreck

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Ok. If it's at WOT it could be as simple as needing to close the plug gap a little. If it's at part throttle it'll take a little more digging. That being said I've had new plugs be bad out of the box and cause issues.

Seriously? Didn’t even know that was possible.
My positive side is saying it’s something small , my negative side is saying down on compression. But i used break in oil and everything.

Ok , he just texted me back it’s misfiring at idle and cruise .........


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01yellercobra

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Seriously? Didn’t even know that was possible.
My positive side is saying it’s something small , my negative side is saying down on compression. But i used break in oil and everything.

Ok , he just texted me back it’s misfiring at idle and cruise .........


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Yeah. I'd check the plugs first. Could be a vacuum leak too. The last set of Autolites I ran had the ceramic separate from the metal. The ceramic would slide down and cover the electrode. That made for an interesting running car. A buddy took me for a ride in his newly finished turbo fox and had part throttle misfires. I asked about the plugs and he said they were Autolites. I told him to check the plugs and the same thing had happened to him.
 

Nervouswreck

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Yeah. I'd check the plugs first. Could be a vacuum leak too. The last set of Autolites I ran had the ceramic separate from the metal. The ceramic would slide down and cover the electrode. That made for an interesting running car. A buddy took me for a ride in his newly finished turbo fox and had part throttle misfires. I asked about the plugs and he said they were Autolites. I told him to check the plugs and the same thing had happened to him.

Didn’t know a vac leak can cause a misfire either . I thought misfires were from either fuel , spark , or compression.
If it’s happening at idle and cruise could that be compression? That’s what I’m worried about


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01yellercobra

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Didn’t know a vac leak can cause a misfire either . I thought misfires were from either fuel , spark , or compression.
If it’s happening at idle and cruise could that be compression? That’s what I’m worried about


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Vacuum leak messes with the A/F which can cause a misfire. I would think if its compression you'd have it at all RPM ranges. Not to mention you'd probably have a smoke issue as well.
 

jwcobra03

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New 02 sensors? I just had a misfire recently at idle. Had the p2195 code. Wound up being a bad 02. As mentioned, plugs can sometimes be bad out the box. Had that happen before. New builds have tiny gremlins. I wouldn't get too paranoid yet. Best of luck.
 

big dad

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The first thing I'd do is get a scanner on it and check for codes and see if it's isolated to a single cylinder or a fuel delivery issue. If you don't know where it's at, find out where it isn't at.
 

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