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Old 04-25-2016, 04:15 PM   #1
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04 mustang stumbles on hard acceleration

I'm not quite sure how to post threads or where to put them or any of that, kinda new to this but i have a problem with my vehicle and need help...

2004 mustang
3.8L

My car drives great mostly, i can drive it like a daily driver without any problems at all, cruises fine, my problem is only when i come to a complete stop and then hit the throttle fast, i don't even have to floor it, just hitting it fast will make it stumble like it dies for a split second and all my gauges go whack and reset like the car is starting up like i just turned the key to crank it(gauges go all the way one way and back to the other).

Like i said, if i just drive it normal, no problems at all, even if i'm already cruising anywhere above 5-10MPH and slam the throttle it'll get up and go, no stumble, its only when i'm at a dead stop and do it...now as far as letting you know what all i've done to the car...

New
255LPH fuel pump
fuel tank itself
fuel filter
cold air intake

i've taken apart every electical connector on the vehicle i can think of and sprayed them with electrical parts cleaner(CRC) and cleaned mass air flow sensor also.

one thing i've noticed is the throttle position sensor(TPS) has 3 wires and one of them is frayed, i've cleaned out throttle body itself too.

My guess is its the mass air flow sensor(MAF) or throttle postion sensor(TPS)

The vehicle also has a SCT tune in it, but problem persists whether i have the tune in or reverted to stock.

I will upload a few datalogs i have of me smashing the throttle from a dead stop, it only monitors MAF counts, air flow, and fuel rail pressure.

Any help would be appreciated, Thx
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Old 04-26-2016, 09:57 AM   #2
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I think you may have answered your own question. You likely need to replace the TPS wires that are damaged. There needs to be a precise voltage flowing to the rest of the system.

If your car has a hestitation upon immediate wide open throttle my first guess is that the engine is starving for fuel. You have replaced several items I would have suggested. I did not see that the fuel filter was replaced though.

Out of curiosity, put the factory air intake assembly on the car and try to go WOT from a dead stop. If that solves the problem then we have a starting point as to what is causing the issue.

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Old 04-26-2016, 08:01 PM   #3
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The gauges sweeping is an indication that the voltage to the PCM is low.
Get your charging system (battery/alternator) tested.
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Old 04-26-2016, 08:45 PM   #4
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Quote:
Originally Posted by straybullitt View Post
The gauges sweeping is an indication that the voltage to the PCM is low.
Get your charging system (battery/alternator) tested.
That is something I didn't know. I have just learned something new.

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Old 04-27-2016, 10:18 AM   #5
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i've had a problem with the battery light coming off and on whenver it pleases, but its been like that for 3 years now, and yes i put in OP i changed fuel pump, fuel filter, and fuel tank itself, the whole fuel system is brand new. i also fixed the TPS wires by cutting and splicing them back together with heat shrink temporarily til i go buy the new TPS sensor on my day off, i honestly think it's something to do with the MAF, but i will get these things looked at and get back to you guys asap
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Old 04-27-2016, 09:25 PM   #6
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Are your injectors big enough to handle the fuel from the new bigger pump when you punch it? But I kind of think you're right on the MAF sensor. That thing can make a car run like crap in all sorts of ways. I think the gauge problem is electrical as was said or maybe just a worn out serpentine belt or tensioner pulley not causing the alternator pulley to turn fast enough to give you the voltage needed when you punch it. Belt could be slipping.
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