Hello,
my daughter generally drives my 2004 Mustang.She called me and said it was running kinda ragged, like it had gotten bad gasoline, and the check engine message had came on. I'd just had it serviced at 55K and it had been running fine. Asked if she'd just put in gas, she had and the cap was loose. Called a friend at the dealership and he said those were typical symptoms but should go away. It's been two weeks and no change. Does anyone have any ideas ? I'm a single parent with two kids and $ is kind of tight so I was hoping for an easy fix. Thanks in advance for any help/advice/tell me i'm an idiot that you folks can offer !
Big_Al_2
my buddy with a 2000 mustang had the same issue, the gas cap wasn't holding vacuum of some sorts. your best bet would be (if the cap is loose) just replace the gas cap and see if that helps.
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1994 Mustang GT 5.0
Mods to date: T5 swap, MGW shifter & Composite race knob, Ram clutch, flowmaster cat back system, BBK o/r h pipe, BBK equal length headers, BBK cold air intake
In the process of a gt40 install along with 4.10's and some other new goodies
the code you're going to have is a p0455 evap emissions gross leak detected. when you leave the gas cap loose pressure wont build up in the evap system and the pcm will detect that leak.
it should have become a history code and gone away after a few miles of driving after putting the cap back on, if it still persists, either disconnect the battery for a couple minutes, or use an obd2 scanner to clear the dtc's. if the MIL comes back on, then you are going to have to dig a little deeper into it.
rmv/rst bat cables. "svc engine" back, still runs poorly.
Thank you. I removed/restored the battery cables, cleared the "service engine soon" but still "bouncing". "service engine" is back now.Not the gas cap, it just wasn't properly screwed back in. 232-K7 thanks for the info and suggestion. I'm sorry but the "obd2 scanner" is beyond my pay grade-I don't know what that is.
Thank you. I removed/restored the battery cables, cleared the "service engine soon" but still "bouncing". "service engine" is back now.Not the gas cap, it just wasn't properly screwed back in. 232-K7 thanks for the info and suggestion. I'm sorry but the "obd2 scanner" is beyond my pay grade-I don't know what that is.
you can probably get an obd2 scanner from autozone for $50 or so. maybe even cheaper. it just plugs into your DLC under the dash, it just reads/clears the codes that come up when your check engine light comes on.
or...autozone can just do that for you for free.
The scanner is $59.99 at Autozone. Also they will not scan and clear it for you. I asked because I still have a CEL after I installed my cold air intake and I got a rather rude "We don't rent tools here."
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'01 Silver V6 5-Speed Show:17x8 Anthracite Bullitts w/Kumho 255-45s, spoiler, smoked headlights and fog lights, black LED 3rd brake light, Mach1 grill delete, Mach1 chin spoiler, splash guards, Hurst badge, chrome exhaust tips, carbon fiber bumper inserts, 8" antenna, black hood stripe, 232 badges, Ford Racing license plate frame (in the box: hood scoop, rocker stripes) Go: Divorced dual exhaust w/Original 40's, AM CAI, Hurst shifter, SCT 91+ Tuned
Well Ive Heard but never had that problem with my Mustang 02 V6. but I think it says in the manual or somewhere that if you don't tighten your gas cap fully, check engine light will come on. So like the others said. Just tighten your gas cap, if that doesent work, then buy another :P and 232-k7 Is a very smart when it comes to Mustangs :P He helped me out
"service engine" msg after gas cap loose. 
that you folks can offer !
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