Random Misfire?

rw95gt

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Im running tr6 plugs and I keep getting a random miss fire code. I had the plugs gapped at .028 becuase I have hit of gas on the car. I pulled the plugs and they all looked clean and regapped them at .035. This helped but it still throws the check engine light after 20 minutes of driving. If you drive it a little more aggresive it will not throw the code but stop and go traffic for 10 minutes or slow moving traffic and it will throw the code.

When the plugs where gapped at .028 it was throwing 2 miss fire codes. The random misfire and misfire cylinder 1. The check engine light would flash and you could clearly feel and hear a cylinder not hitting. If you gave it some gas it would clear up. I checked all the fluids and they are fine and clean.

Any thoughts?
 

rw95gt

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The car has 5000 miles on it. It has never had leaded gas in it. The plugs have 800 miles on them. I just regapped them. Should i try a differant brand or a new set? I cant remember the number off the top of my head but it was a random misfire code and misfire cylinder 1.
 

bull3441

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if the plugs are good like you state, then next step is to check the MAF. rule out the simple stuff. plugs, maf, fuel delivery etc.
 
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UnleashedBeast

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Every time I've received a random misfire code, I forgot to plug in a fuel injector.

Have you had your engine taken apart recently that required unplugging the injectors? Check to make sure all 8 are plugged in firmly.
 

Robertt305

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Id try first a new set of plugs ..... Whatever brand you want, and reflash the car...

I had a same issue with a set of plugs that only had 8 passes and maybe 20 street miles....

Got new plugs reflashed her and all was well.....you can't always go by how a plug looks, sometimes they have issue right out of the box...
I change plugs every track outing and oil change along with my fuel filter....
 

rw95gt

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Thanks fellas. I am going to check and be sure everything is plugged up. Fuel injectors and all. I havnn't had them unplugged but its possible something worked itself loose. I am going to pick up some new plugs and a fuel filter today.

What gap do you recomend? I was just thinking the computer doesn't like the tr6 plugs or them being gapped tight.

Getting ready to drive it to work today. Im going to clear the code and write down what it is and see how it does today. Yesterday I drove it to work the gym and on thw way back home in stop and go traffic the check engine light popped up.
 

Robertt305

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Not sure what plug or gap works best with spray... I'd personally pull the battery or reflash it to clear everything and start fresh along with those items your getting..

If it persists then id start by testing coil packs...
 

rw95gt

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I reflashed it this morning. .035 is to much plug gap. Im going to try .032 with new plugs. Prob get them in this weekend and i will update the thread.
 

stkjock

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I would suggest swapping the COP from #1 to #3 and see if the misfire code moves to that cyl.

if it does, it's the COP
 

rw95gt

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No shift light wired up. I will move the coil when I change plugs. Good Advice.
 

jroush06

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I'm having the same issue with my compound boost GT500. Took it to the track recently and ran it on C16. Changed the plugs and gapped them at. 30 and reflashed the computer back to the pump gas tune. Car only throws a random misfire code on start up only and only does it about 1 out of 4 start ups. Never throws a code while im driving it or getting into boost. Any thoughts?
 

PRP

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I was just thinking the computer doesn't like the tr6 plugs or them being gapped tight.

It might not.

I had a car come in for a smog check and it failed. The owner had just 'tuned it up' and installed new plugs. The problem was that he didn't gap the plugs out of the box and the plugs were gapped too tight. That made the spark duration too short and didn't burn all of the fuel in the chamber causing high HC (i.e. misfire) and CO ('too rich) due to the unburned fuel caused by a spark that wasn't long enough (in time).

I found it with a O-scope, pulled the plugs, regapped to Mfgr. spec, re-installed them and passed the (Calif) smog check with flying colors. In fact, that car (a Ford mini van) had the highest CO2 reading (an indication of engine efficiency) I've ever seen on a car (almost 17%).


Phill
 

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