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Misfiring after 100mph!

ricio1991

ricio1991

New member
Okay guys i have a 2004 grand prix gtp competition package and it has 102k miles. Got the car checked out by a shop because of a random misfire after like 100mph or more. Only on freeway in the streets its fine no codes thrown or anything. Mechanic said start with a transmission fluid replacement and see from there and still charged me not answering why it was misfiring. He said everything looked good. What should i do. I changed the fluid in the transmission 2 weeks ago at another shop. Car runs great until 100 and more! Please help I'm tired of paying mechanics for no answers!
I was thinking of taking it to gm


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Yes its on and off. Yesterday was driving down the freeway. One pull i did full throttle and around 100ish it started flashing. So i let go off the gas because i don't want to damage anything. So i wanted to see it again to try to figure out if it happening constinetely and i did a pull to 110mph and no flashing. So it really weird


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What kind of plugs did you install? Also, did you reuse the old wires? The flashing is showing a possible catalyst damaging misfire as you seem to know.
 
Thats doesn't sound good! I already have changed the catalytic converter i got warranty but still would suck to pay labor again. New bosh wires with ngk i believe.


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Its been about 10k miles since i did the wires and plugs. I did the catalytic converter also with 02 sensor. Why would it happen only at high speed possibly overdrive


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Correct! It only happens at wot high speeds! But not at low speeds. I can full throttle from a dig and go and no problem


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I know i don't but i want to fix the problem or just fix it. Im just trying to conclude wether i should get rid of it or not. Cus if its serious i don't want to deal with it. But yes i understand but these cars are pretty strong they shouldn't have a problem at 100mph. I wish it was running 100 percent


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Thanks whats freeze frame data? I may get a second opinion by a gm mechanic here in my city hes very familiar with gm cars


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Yeah i already put in like 2k of mechanic work in the last year and a half!!!


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You're Probably getting a ton of kr and the motor hates it. You'd need to scan for kr and see what you're getting
 


I wont be doing pulls until i find out exactly issue and fix it. Ill see thanks for the information tho


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