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Old 04-29-2014, 09:26 PM   #1
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My GT is slow and rough. is that normal?

Hi. Im new to the forum, but Ive been lurking for a couple years. I recently bought a 2002 GT as a daily driver. It's my first 4.6. It has 91,xxx miles and stock as far as I can tell. It has 3.73 gears, auto, coupe. After purchase, I immediatly changed plugs (autolite plats), fuel filter, air filter, cleaned MAF, cleaned IAC, replaced EGR, fixed vacuum leak, changed oil and trans oil, and unplugged battery to reset ECU.

It has no CEL or pending codes according to my Actron scanner.

pre-tune up it ran 7.9 sec 0-60 with trac off
post-tune up it runs 7.6 sec 0-60 with trac off
my 2012 base 3.7 auto with 2.73s runs 6.9 sec 0-60 on the same stretch.

it feels really rough, loud, and restricted, but still has enough torque to squeal tires at launch and sometimes chirps shifting into second.

The idle is inconsistant and occasionally stumbles to an almost stall, especially when heat or a/c is on. It also sometimes lurches during acceleration and temporarily feels smoother and faster (feels great!), but always returns to the grumpy restricted feeling right afterward.

Actron says TPS is at 19.2% during idle and 92.6% at WOT.

Is this car normal? I have zero experience with this car/engine and I dont know what to expect. I realize its not a race car in stock trim, but Ive read that the factory spec is supposed to be sub 6 sec 0-60, and this car is far from that mark.

Any advise and help is appreciated. TIA, Jeff
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Old 04-29-2014, 10:57 PM   #2
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it also doesnt want to start sometimes... especially after i have been driving it hard. it will crank over fine, but just doesnt fire up. it always starts fine from a cold start.

The alternator seems fine... its runs normaly after I disconnect battery, even with lights and radio on.

it sounds and feels "grindy". no pinging, but sounds like it labors to pick up rpms, it feels "heavy". I was expecting it to rev up faster and decel faster then it does.... maybe im just used to the cyclone 3.7

To me, it feels like bad timing, but I dont know how thats possible. if the chain skipped a link, I think it would run worse, or not at all. And sometimes the engine feels light and quick, but its only temporary and quickly goes away. My uneducated guess would be that it had Variable Valve Timing that was malfunctioning due to bad cam phasers or hydrolic actuators, but I dont think this engine has those.

Also, the engine oil has no signs of frothing from coolant. its clean and clear. No overheating either (confirmed by Actron)

My next guess would be cam/crank sensor, but theres no codes pending.

that leaves me with TPS... But I dont think it could cause such issues.

Hopefully someone here can lend some insight.
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Old 04-29-2014, 11:03 PM   #3
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gritty
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Old 04-29-2014, 11:08 PM   #4
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gritty? as opposed to "grindy"? I guess thats an accurate description.
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Old 04-30-2014, 09:11 AM   #5
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My GT is slow and rough. is that normal?

Not sure man... I know our gt's stock form can beat a stock 3.7... I know that i slammed my car once and was unimpressed by second gear... Third definitely seemed to be the "go" gear. In my 99v6 it was second gear that was hella strong.

Maybe you are just used to the gearing of your 3.7 and it's different for your GT.

Btw, how are you doing your 0-60's? Because your speedometer is off if you have gears with no tune. Maybe that's throwing your times off.
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Old 04-30-2014, 09:38 AM   #6
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according to the VIN check at Ford Etis, this GT came from the factory with 3.73s

My wife and I just raced my 2 stangs. She in the 3.7 and me in the GT. The results were just as the times I posted. the 3.7 was a couple car lengths ahead when she let off around 75 mph.
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Old 04-30-2014, 10:02 AM   #7
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Quote:
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according to the VIN check at Ford Etis, this GT came from the factory with 3.73s

My wife and I just raced my 2 stangs. She in the 3.7 and me in the GT. The results were just as the times I posted. the 3.7 was a couple car lengths ahead when she let off around 75 mph.

Um.. Is this a normal GT? Because they came with 3.27's (I believe)
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Old 04-30-2014, 10:09 AM   #8
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ya. i guess so. 2002 Mustang GT Premium Coupe.
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Old 04-30-2014, 11:21 AM   #9
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Just reran VIN at Ford Etis:

Build Date: 10.06.2002
Vehicle Line: Mustang
Body Style: Coupe
Version: GT
Engine: 4.6 SOHC EFI
Transmission: 4R70W (AODE) 4-Speed Auto Trans
Drive: LHD RWD
Axle Ratio: 3.27

I could have swore that it said 3.73 last time I ran it.... maybe I typed the VIN wrong.

So ya, 3.27 gears.

Heres some Actron readings at warm idle:
MIL STATUS OFF
ABSLT TPS% 19.2 (92.6 at WOT)
CALC LOAD% 26.2
MAF FLOW GR/SE 5.31
IAT F 51
IGN ADVANCE DE 28.0
FUEL PRESS KPAG 273
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Old 04-30-2014, 11:26 AM   #10
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Rebuild your COPS, its only $30 to get the new boots/springs and the actual electronic portion itself rarely goes bad. Or buy all new ones to the tune of $350...
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Old 04-30-2014, 11:28 AM   #11
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Clean the maf element with electronics cleaner and ensure iac is functioning properly. Sounds like a computer issue dealing with air flow.

Btw...the 2v in stock form really is boring after initial hit. No real exciting gear.

Sent from my massive johnson.
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Old 04-30-2014, 11:45 AM   #12
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Thanks guys. I have a 2004 5.4 Triton F150 FX4 and I am pretty familiar with bad cops. It doesnt have the banging misses that my truck experiences when a cop goes out. Also, my Actron misfire check comes up clean. But thanks for the advice. I will clean the cops up just to be sure.

I cleaned the MAF with MAF spray cleaner and even gently wiped the wires with an artists paintbrush soaked in MAF cleaner. Afterward, I checked the MAF by unplugging it and running engine...It threw a code for IAT. plugged it back in, cleared CEL and code disappeared.

I also cleaned the IAC with Motorcraft choke/carb cleaner, then sprayed it out with the MAF spray to remove residue. This was all part of my tune-up.
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Old 04-30-2014, 11:49 AM   #13
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Quote:
Originally Posted by lowflyn View Post
Clean the maf element with electronics cleaner and ensure iac is functioning properly. Sounds like a computer issue dealing with air flow.

Btw...the 2v in stock form really is boring after initial hit. No real exciting gear.

Sent from my massive johnson.
This is truth. I can get going pretty goddamn fast from initial launch with the gears but the 3rd and 4th gear pulls... needs more...

At any rate does the car pull ANY other codes even with the CEL off? Maybe your cam chains are loose and jumped a tooth?
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Old 04-30-2014, 12:04 PM   #14
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Nope. No pending codes. It feels like out of time, but no codes, and sometimes it wants to run smooth and fast out of nowhere.
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Old 04-30-2014, 12:06 PM   #15
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If it jumped time, would it still run? or wouldnt it run even worse than it is?
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Old 04-30-2014, 12:15 PM   #16
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If it jumped time, would it still run? or wouldnt it run even worse than it is?
It absolutely would NOT be running. You'd be buying new valves and maybe pistons for whichever bank jumped time.
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Old 04-30-2014, 12:17 PM   #17
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And REPLACE your IAC! Cleaning them does no good when they're worn out.
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Old 04-30-2014, 12:18 PM   #18
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gritty
Haha.
It'll catch on FA.
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Old 04-30-2014, 12:34 PM   #19
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Haha.
It'll catch on FA.
lol its an accurate description
.. my car feels gritty when I accelerate, not smooth like you would expect.
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Old 04-30-2014, 01:44 PM   #20
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is the word gritty some kind of inside joke?... cuz i dont get it
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Old 04-30-2014, 01:50 PM   #21
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is the word gritty some kind of inside joke?... cuz i dont get it
acceleration
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Old 04-30-2014, 02:01 PM   #22
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YES! Thats what I am feeling too! Gritty! You ever get that figured out FA?
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Old 04-30-2014, 02:54 PM   #23
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pretty sure ford just built gritty engines
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Old 04-30-2014, 03:05 PM   #24
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And REPLACE your IAC! Cleaning them does no good when they're worn out.
I think im gonna have to.

I just replaced the TPS and did a idle relearn, but it still dives. However, it does accelerate a bit harder....but still gritty

tried to do a new 0-60, but I cant keep the rear from spinning out now
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Old 04-30-2014, 04:03 PM   #25
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let me know if you figure it out
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Old 04-30-2014, 04:56 PM   #26
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will do
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Old 04-30-2014, 06:56 PM   #27
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I have a 2000 gt auto as well all stock. The stock gearing is not that good on the auto. My brothers 06 fusion auto with a v6 gets up faster than my mustang. Although if I hold it in first and floor it then shift to second it will still chirp the tires.
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Old 04-30-2014, 07:42 PM   #28
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Just for experimentation, I filled up with high octane gas.... now its running super rough! Sounds like I filled it with sand. Wtf
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Old 04-30-2014, 08:03 PM   #29
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how's the engine sound?.. exhaust leak?.. video?
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Old 04-30-2014, 08:17 PM   #30
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I should try to get some audio/video of it tomorrow for reference. It's hard to describe the sound, but it doesnt sound healthy.... I guess it sorta sounds like gargling mouthwash.
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Old 04-30-2014, 08:31 PM   #31
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I should try to get some audio/video of it tomorrow for reference. It's hard to describe the sound, but it doesnt sound healthy.... I guess it sorta sounds like gargling mouthwash.

Yeah... My car doesn't sound healthy either... I think it's detonation but it's probably just the engine in general. I may be worrying about nothing. My gf's v6 does it also but not as bad as mine.
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Old 05-01-2014, 03:35 PM   #32
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Ok FA, I shot some audio/video with my GS4... but i dont know how helpful it will be..

After watching it, I said to myself, "Damn, my car sounds pretty f*ckin cool!". Lol!

I guess the "grittyness" is more of a feel than a sound.

I will post it up if u want to see it, but it may make me sound like an idiot! Lol
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Old 05-01-2014, 04:04 PM   #33
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lol yeah mine is a feel. just feels clapped out but I know its not.. something seems restrictive.. But I have such an extensive build plan that it doesn't bother me much!... Your issue seems a bittttt more serious then mine maybe?.. ahh post the video anyways haha
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Old 05-01-2014, 04:10 PM   #34
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once I get some time and a few extra dollars I plan to
pull the plugs and do compression tests
clean the injectors or replace them, replace the cop's and the plugs.
clean my maf, replace my pcv valve, replace my iac, tps, clean my throttle body, flush and fill my coolant, change my oil/filter and change my fuel filter..
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Old 05-01-2014, 04:57 PM   #35
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ya, Ive been cleaning and reinstalling the cops today. the fact that it was worse with high octane sounds to me like general misfiring, even though there is no codes or obvious misses.

Id like to get some new ones, but dont want to shell out the cash for motorcrafts. I use Global cops in my FX4, but they done sell the DG508s, just the DG511s. I have some spare 511s, but they wont fit in the 4.6

Ill post the vid in a bit.
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