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Discussion Starter #1 (Edited)
06 GTO randomly misfiring, suggestions welcomed

Car has 15k miles on it, sometimes it will happen after 30 minutes of driving, sometimes I can drive it for 2 hours straight and not have it happen.


Randomly the check engine light will start flashing and there is definately something not right with the car when that happens, feels underpowered, sounds like it's breaking up, a misfire.

Usually after 15-20 seconds, the light will stop flashing and the car will quit acting like it's misfiring terribly, but it has not felt quite right since this first happened 3 days ago.

The last time that it happened, the light was flashing, the car felt like crap, and then all of a sudden the light stayed solid, so I hooked up my scanner and pulled the code, Cylinder 7 Misfire.


Turned the car off for about 30 minutes, started it again, CEL was off.

It has done it probably 6 times the last couple days, it has never stayed solid again though, blinks for 15-20 seconds, feels like crap, goes away.


Any ideas? I would assume spark plug and/or wire but I haven't had a car that did this randomly, usually when I've had a spark plug/wire go bad it was constant until they were replaced.


Thanks in advance.
 

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Discussion Starter #3
Random as far as it comes and goes with the light blinking and performing poorly, the only time I was able to scan it was the once that the light became solid and it said Cylinder 7 Misfire.
 

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Twin Turbonaro
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If it's only misfiring on #7 cylinder, try swapping that plug lead first......then the spark plug......then the coil with another cylinder to see if the fault moves or stays on #7, then you should be able to track down the culprite....let us know what you find. I've seen plug wires and coils go intermittent.
 

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Southside Tuner
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647 Posts
Mine has does that, turned out that it was caused by poor quality fuel in country towns. Its deffinately something to look out for, I used to work for Shell "Not at a station" but for the fuels division, and sometimes our premium gas would sit for awhile especially when its 4.18 a gallon. And over time the 93 fuel would degrade possibly lower than 89 octane? Which in a performance car can cause pinging poor performance and ramndom misfire?

Thats just what has caused mine to go off in the past. If there is no mechanical problem, try changing to the busiest name brand fuel station in your town, at a busy station fuel does not sit as long and tends to be fresher. This has worked for me.
 

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Twin Turbonaro
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740 Posts
Mine has does that, turned out that it was caused by poor quality fuel in country towns. Its deffinately something to look out for, I used to work for Shell "Not at a station" but for the fuels division, and sometimes our premium gas would sit for awhile especially when its 4.18 a gallon. And over time the 93 fuel would degrade possibly lower than 89 octane? Which in a performance car can cause pinging poor performance and ramndom misfire?

Thats just what has caused mine to go off in the past. If there is no mechanical problem, try changing to the busiest name brand fuel station in your town, at a busy station fuel does not sit as long and tends to be fresher. This has worked for me.
If it was poor quality fuel, wouldn't he be seeing random misfires on other cylinders as well ? Just a thought. Manufacturers should put octane gauges in cars so we can see when we get bad gas.
 

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Discussion Starter #7
I've had the car for about 5 months and have been filling up at the same station, the highest available in this area is 91, but this is the first time its acted this way, I fill up at Smiths here.

I had an 01 TA WS6 befor this car for a year and didn't have these issues, but I will keep that in mind for sure.


Thanks for all of the helpful responses.
 

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Capital City GTO's
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Since the car only has 15k miles on it, why dont you take it to the dealer?
 

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Suffering Fools
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Random as far as it comes and goes with the light blinking and performing poorly, the only time I was able to scan it was the once that the light became solid and it said Cylinder 7 Misfire.
OK "random misfire" is a separate code, and that happens when the misfire really is random. As in, it's happening on different cylinders. What you have is a misfire on cylinder 7.
 

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Discussion Starter #10
Yes, it is randomly misfiring on Cylinder 7, I did not mean to cause confusion.
 

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Discussion Starter #12 (Edited)
Yes, in random intervals.

There was nothing wrong with my choice of words, I clearly stated what events were happening in the body of the post.

Thanks for the help.
 

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BYAH!
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its a coil/wire/plug... fords do this all the time... just replace that cylinders set-up and you'll be golden!
 

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Car has 15k miles on it, sometimes it will happen after 30 minutes of driving, sometimes I can drive it for 2 hours straight and not have it happen.


Randomly the check engine light will start flashing and there is definately something not right with the car when that happens, feels underpowered, sounds like it's breaking up, a misfire.

Usually after 15-20 seconds, the light will stop flashing and the car will quit acting like it's misfiring terribly, but it has not felt quite right since this first happened 3 days ago.

The last time that it happened, the light was flashing, the car felt like crap, and then all of a sudden the light stayed solid, so I hooked up my scanner and pulled the code, Cylinder 7 Misfire.


Turned the car off for about 30 minutes, started it again, CEL was off.

It has done it probably 6 times the last couple days, it has never stayed solid again though, blinks for 15-20 seconds, feels like crap, goes away.


Any ideas? I would assume spark plug and/or wire but I haven't had a car that did this randomly, usually when I've had a spark plug/wire go bad it was constant until they were replaced.


Thanks in advance.
I have the same problem,#7 and #8 miss fire.I had to replace my crank posisitioning sensor a week before this happened,after I got these codes of miss fire,I took my car to Advance Dyno since they have done my mods and tune,Robert found that my cats were coming apart,so I went ahead and ordered my Kooks with cats but I am waiting for them to arrive.He drove my car for a few days to see if it would miss while driving,it didnt.He noticed my cats were bad after they installed my Magnaflows because of sound of something loose in my exhaust after install, they removed the exhaust and found bits of cat material,he never saw any codes on the computer since my CEL never came on, prior to taking it to him CEL came on and I took it to dealer since they did the crank pos sensor,the miss fire occured after I picked it up from dealer,they wanted to charge me since I had mods,warranty goes out the door,I hope my problem goes away with the Kooks and cats install,sorry for the long story but we have the same issues and maybe this can help you...I posted in Tech more details...Good Luck..
 

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GONE was here FIRST!!!
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Mine just started to do this too. Lower RPMs though. Feels heavy and underpowered. I bought a set of plugs today and I'm gonna throw them in this weekend. I have 53k and I just had mine tuned almost a month ago. I checked my gas receipt last night to see if I got the wrong gas but it reads PREMIUM. I think when the previous owner tuned the car the tune richened the mix and fouled the plugs. Who knows?
 

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Do you have an auto or stick? if an auto does it have an stall converter?
 

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The Artist Formerly Known as Herpes
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I had the exact problem you are having (same codes same cylinder).

It started after my motor was rebuilt by the dealer at 10,000 miles. It took 6 months and 5 different dealers to figure it out, turns out that when the motor work was done they forgot to reset the crank position sensor.

Not sure if it is your problem, just throwing out ideas
 

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