What does and engine misfire sound like? need help

Discussion in 'SN95 4.6L Mustang Tech' started by BigChiefSmokem, Oct 10, 2005.

  1. I made a thread recently about my exhaust problems, one of those problems was that when i rev it up and hold the rpms anywhere between 1500 - 2500 rpm you hear a "thump/pop" coming from the exhaust. Its intermittent and often, and sounds exactly like if you tapped a bass woofer with your finger. The car has not thrown a check engine light. would this sound be cause by a misfire?

    So i took the car to my local mechanic, whom i trust, and he said it sounds like a misfire to him, he can hear it even at idle. He also says that he cannot pinpoint the exact cylinder that its doing it b/c on fords, unless its throwing a code, there is way to tell which cylinder is misfiring. Is this true?

    a little history: I had what i felt to be slight hesitation at 2k rpm recently until i used seafoam yesterday, and that went away...

    About 2-3 months ago all of a sudden the car would shudder and buck and not go anywhere quickly in all gears when i gave it even more than a 1/4 throttle. the exhaust also made a clearly audible and consitent huff/pop noise under throttle that coincided with the firing of the cylinders. So i took it to my local mechanic, had them replace spark plugs, fuel filter and do a fuel system cleaner, as i had no idea what the problem was, and it was about time for that stuff anyway. Problem went away. They told me one of my plugs was extremely foul, and that could have caused the problem. they also mentioned to me that a coil pack was beginning to go bad... I have them checking their records to see if we can pinpoint which one of the plugs was bad...

    So.. with that said, any suggestions or advice?
  2. sounds like a misfire to me

    my friends 99 gt did the same thing, and bad. It would do that slight pop/hesitate and would buck under acceleration (kinda like the a/c compressor kicking in randomly and often)

    check your plugs/wires again, and definitely have someone check the coil packs. I believe the coil packs were the culprit on my friends car.

    good luck
  3. what you said describes a misfire pretty well. sounds like you may have already found the problem. a bad coil can cause a weak spark which will foul plugs. the mixture is very rich at low rpms making it more prone to misfiring. I had a problem with my spark plug wires a while back and either sanding down the plugs, or replacing them would fix it for about 500miles. if all the plugs are fouling, then its likely the maf or one of the o2 sensors have gone bad.

  4. Thanks for the speedy response guys. From what i can remember they said that the plugs did look pretty bad, but it had been 60k miles since they were changed. but one in particular looked very bad, which i think caused them to think that there may be a coil pack going bad. I'm having them check their records to see which cylinder they pulled the plug from 2-3 months ago. I may have them pull all the plugs and see if they can find any that look bad.

    also, is it true about without the engine putting out a code it is hard to tell which cylinder is misfiring?

    he also told me a coil pack would be $90 bucks... per cylinder.. is this true?

  5. Off topic: crazynorwegian check you PM's.
  6. a coil pack is what makes the spark plug well spark and it replaces the the distributor less system from the 96-98 mustangs.......... they are located on each cylinder head right where the fuel rail next to the injectors
  7. The lack of acceleration when you step on the gas was the giveaway symptom of a misfire. I had the same thing happen to me, and what caused it was dirt and all sorts of debris in the actual plug boot, where the little metal coil is located. I just cleaned those out real well and no problems since. And if you "wash" your engine bay, then this could definately be the reason.
  8. i did wash my engine bay, but that was 4-5 months ago.... it was hesitating after i washed it... but it went away the next day... and then, what happened that caused me to replace the spark plugs happened, but i forget how long it was after i washed my engine that that happened...
  9. is there any chance that the computer would throw a code without the CEL coming on?