2003 mustang GT Misfiring - Ford Mustang Forum
 
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post #1 of 7 (permalink) Old 07-10-2010 Thread Starter
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2003 mustang GT Misfiring

03 mustang gt 56,000
sct tune 93 oct
Full exhaust no headers
4.10 gears
Accufab, Typhoon intake, throttle body don't know the size

My gas milage has stedly been decreasing alone with power. I have a little big of smoke coming out of the exhaust it is very light smells like gas no OIL! You know when you unplug the injecter off you can hear it pop right? Well you can hear that pop threwout the idle. It does it every couple of seconds and sounds just like a misfire. The car was orginally idling ruff, so I changed the IAC. Better Idle IAC was shot. It still jumps from 840 Rpm to 750 while in idle. If you listen very carefully just above the first two right cylinders. You can hear a very noticible tapping. Almost lost to a civic something is wrong I promise you and it wasn't boosted or cammed so I know its something.

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post #2 of 7 (permalink) Old 07-10-2010
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Quote:
Originally Posted by UncleMcMicheals View Post
03 mustang gt 56,000
sct tune 93 oct
Full exhaust no headers
4.10 gears
Accufab, Typhoon intake, throttle body don't know the size

My gas milage has stedly been decreasing alone with power. I have a little big of smoke coming out of the exhaust it is very light smells like gas no OIL! You know when you unplug the injecter off you can hear it pop right? Well you can hear that pop threwout the idle. It does it every couple of seconds and sounds just like a misfire. The car was orginally idling ruff, so I changed the IAC. Better Idle IAC was shot. It still jumps from 840 Rpm to 750 while in idle. If you listen very carefully just above the first two right cylinders. You can hear a very noticible tapping. Almost lost to a civic something is wrong I promise you and it wasn't boosted or cammed so I know its something.
I have the same problem. Expirement with the Plugs, coils and if you know its neither of them, then its the injector. My problem i found is a bad injector that i need to replace. Is it throwing a code? Mine didnt till it got very bad and i found it was on Cylender 7. I have the exact same symptoms. It would like drop RPMs, feel like it'd about to stall, and then the RPMs would jump back up and the stall feeling goes away. Put in a bottle of Lucas fuel system cleaner and see if the misfiring goes away. Thats how i could tell it was a bad injector causing it to misfire. Goodluck.

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post #3 of 7 (permalink) Old 07-11-2010
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i got the same symptoms, sounds like coils to me.
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post #4 of 7 (permalink) Old 07-11-2010
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Wow, didn't realize a misfire was so popular. My dad's stang is doing this also. We had to replace coil and plug on 5 and she runs good now

03 Mach 1: New toy
00 Kenne Bell GT vert: Sold
04 Sonic Blue GT: Missed
96 GT: First. Sold.

06 F250 6.0L 4x4: Studded, EGR delete, IDP tunes, 5" Straight pipe, S&B CAI
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post #5 of 7 (permalink) Old 07-15-2010 Thread Starter
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Quote:
Originally Posted by 04sonicbluegt View Post
Wow, didn't realize a misfire was so popular. My dad's stang is doing this also. We had to replace coil and plug on 5 and she runs good now

Yulp same here coil on 5 and did the plugs 100% better fixed!
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post #6 of 7 (permalink) Old 07-16-2010
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yeah im about 90% its the coils been there done that, and im actually going thru it again due to sum terrible GMS coils. im going with MSD this time, its so annoying how much power a failing coil robs
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post #7 of 7 (permalink) Old 07-17-2010
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my gt first was saying codes for my massair meter.... then I reset it...
Then I had multiple misfires at 1000 rpms and 1,3,5,7 misfire...
Replaced plugs car ran amazing for 30 minutes now nothing
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