i have an 02 gt with 47k miles. during idle it fluctuates about 200rpms, and has a "pop" to it. the best way i can think to describe it is you can hear it misfire in the exhaust since i have an o/r h pipe. ive replaced all the plugs and cleaned the maf but that as far as ive gotten. it is smooth as can be on the throttle its just at idle. it also has a mac cai which ive cleaned.
common causes for misfire?
stang0246l
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i have an 02 gt with 47k miles. during idle it fluctuates about 200rpms, and has a "pop" to it. the best way i can think to describe it is you can hear it misfire in the exhaust since i have an o/r h pipe. ive replaced all the plugs and cleaned the maf but that as far as ive gotten. it is smooth as can be on the throttle its just at idle. it also has a mac cai which ive cleaned.
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7,076 Posts
bad coil on plug, vacuum line leak, loose plug. since you say it doesn't miss at WOT i'm guessing vacuum leak. that will show up at idle but not at WOT as there is no vacuum in WOT.
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4,562 Posts
+1 on the coil on plugs, make sure the boots are in good shape. Check those vacuum hoses too, lots of them on the 4.6, and they cause lots of issues when they're leaking.
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3,188 Posts
i have this same issue...ever since i washed my motor
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98 Posts
I have this prob on my Mach. It runs great under power. At idle or coastdown you can hear it popping. I have changed the plugs. All of the old ones looked to be firing fine. Sounds like I will be chasing a vac leak. Oh so fun!:crazy
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255 Posts
You cant spray the coils when you wash your motor IF you do (I had to when i got my car cause it was such a mess) Wash it when you have plenty of time to dry it because you can wash it pull the coils and dry everything out yourself if you don't water gets in there and will cause problems
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12,180 Posts
I would look at cleaning the IAC and then see what the COPs look like.
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Sorry but what and where the IAC. is it similar to cleaning the maf?
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505 Posts
good explanation. thats my problem exactly minus feeling it while revving slowly
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505 Posts
cleaned the iac today, there was some black inside the hole in the intake but after cleaning it all out still has a pop in the idle.
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3,188 Posts
check for vacuum leaks....thats what i thing mine is somewhere.
ill be hose clamping all the hoses down tight under the hood. the the hose going to the iac vallve and the tube going to the driver side valve cover. let it run and spray some carb cleaner around till it stumples then you find your leaking point
ill be hose clamping all the hoses down tight under the hood. the the hose going to the iac vallve and the tube going to the driver side valve cover. let it run and spray some carb cleaner around till it stumples then you find your leaking point
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505 Posts
Update... i changed the plugs toward the end of last summer, i cleaned the iac and maf recently, i checked all my cops today and a few have small cracks in the very bottom of the boot and i only had one spare so i used it on the only one that was actually sliced and it didnt solve my misfire. i also put clamps on all my vac lines. i have no idea whats causing this?
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1,053 Posts
Get an air gap tester for your coils and check them all. Set the gap to 3/8-1/2 on the tool and watch the spark to see if it travels across the gap. Put the end of the tool in the coil on the spring and the clamp end to a ground. Remove the fuel pump fuse (#14 under hood) until it stalls out and have someone crank the motor briefly while you watch the spark. I checked all my coils and they all gapped 3/8-1/2...however i noticed one had an orange spark and all the rest had a blue...weak spark. Also if it only happens at idle try disconnecting each coil one by one and see which one makes no difference if it is something noticeable.
I recently had a misfire and this is how i fixed it. credits to Cliffyk
I recently had a misfire and this is how i fixed it. credits to Cliffyk
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505 Posts
was your misfire noticeable under throttle? did it feel sluggish at all? mine feels completely fine when driving it but ill give it a try.
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1,053 Posts
mine was very noticeable while driving...did you clean your iac yet? maybe clean your maf also and throttle body
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505 Posts
Yes I've cleaned both and the throttle body was replaced with a 75mm accufab
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