2007 gt acceleration problem - Ford Mustang Forum

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post #1 of 83 (permalink) Old 01-04-2017 Thread Starter
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2007 gt acceleration problem

So a couple days ago after filling up gas at the pump, I tried accelerating around 50% throttle and my car did this thing where it like had absolutely no power then lurched forward..So obviously I let off the gas. And as days go on it keeps getting worse.

Now if I try to accelerate at all it pretty much does this, or it basically just has no power at all and the rpms stay at whatever they were originally.

The weird thing is, if I just drive normal without accelerating very hard everything is fine, and the car still idles great.

If I put the car in neutral and rev up the engine it usually will rev up fine, but sometimes it still does the loss of power thing mentioned above.

So, is my car misfiring? I don't hear any weird noises like you usually would with a misfire.
Is my throttle position sensor bad so the engine is getting mixed signals?
Bad coils, what?! Lol.

One other weird thing, if I'm in way higher of a gear then I need to be, like let's say 5th gear when I should be in 3rd..If I put the pedal to the floor it doesn't do anything weird..

Some things you may want to know:
2007 mustang GT manual
51k miles. 😎
Cold air intake
62mm dual throttle body
Xcalibrator2 tuned(need a newer one)
Running 93 octane.

I believe that is about the only engine related mods.

I don't believe coils/plugs have ever been changed.

I did clean the throttle body/maf sensor about 3 months ago.

Let me know what you guys and gals think, thank you very much! 😊

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post #2 of 83 (permalink) Old 01-04-2017
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sounds like a fuel delivery issue. I would start by replacing the fuel filter. its under a plastic cover under the drivers side, about under the front seat. some need a ford fuel line tool, some are said to use the plastic push on clips like the PVC hoses on the intake to valve cover. my 05' needed the fuel line tool. replace that and report back. after that, you can check fuel pressure at the fuel pressure regulator on the drivers side fuel rail. you might be able to hook up your Xcal and check some parameters. if after the fuel filter replacement, your results are the same, id look at your TB. is it an aftermarket like BBK? good luck

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post #3 of 83 (permalink) Old 01-04-2017 Thread Starter
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sounds like a fuel delivery issue. I would start by replacing the fuel filter. its under a plastic cover under the drivers side, about under the front seat. some need a ford fuel line tool, some are said to use the plastic push on clips like the PVC hoses on the intake to valve cover. my 05' needed the fuel line tool. replace that and report back. after that, you can check fuel pressure at the fuel pressure regulator on the drivers side fuel rail. you might be able to hook up your Xcal and check some parameters. if after the fuel filter replacement, your results are the same, id look at your TB. is it an aftermarket like BBK? good luck
I forgot to mention, but I changed the fuel filter a couple months ago as well.
Should I change it again?

What specifically should I check with the throttle body? Yes it is BBK.

Thank you for the reply!

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post #4 of 83 (permalink) Old 01-04-2017
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IMHO I believe it's the throttle body. I've seen people on forums having all kinds of weird issues and when they switch back to the stock throttle body, everything gets fixed. The only throttle bodies these cars work well with are the stock ones and the Ford Racing/Gt500 throttle body. I understand this might be difficult for you as your car is tuned and I'm not sure if you have the stock parts/tuner on you. It also could very well be a fuel delivery issue like the guy above me mentioned as that's something I thought could be the issue as well. While reading your post, I was wondering if you had an aftermarket throttle body until I saw you did at the bottom of your post.
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post #5 of 83 (permalink) Old 01-04-2017 Thread Starter
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IMHO I believe it's the throttle body. I've seen people on forums having all kinds of weird issues and when they switch back to the stock throttle body, everything gets fixed. The only throttle bodies these cars work well with are the stock ones and the Ford Racing/Gt500 throttle body. I understand this might be difficult for you as your car is tuned and I'm not sure if you have the stock parts/tuner on you. It also could very well be a fuel delivery issue like the guy above me mentioned as that's something I thought could be the issue as well. While reading your post, I was wondering if you had an aftermarket throttle body until I saw you did at the bottom of your post.
Why would it be the fact that it's an aftermarket throttle body? It has been on the car since I got it and it has been fine. What specifically is wrong with the throttle body?

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post #6 of 83 (permalink) Old 01-05-2017
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Could this possibly be an Evap system issue? If the tank was overfilled and excess fuel went in to the evap system could this cause these symptoms? Or perhaps a leaky fuel cap. Just not bad enough to cause the CEL to come on yet? I only ask since the issue seems to have happened after refueling.

A while back I was cruisin' about 75mph on the interstate when all of a sudden the engine lost power and then surged a bit and then leveled out. It was almost as if I hit the rev limiter. The CEL light came on. When I made it home I pulled the code which indicated an evap issue. First suggestion was to check the fuel cap, which I did by loosening and then firmly re-tightening it. I had refueled a few days prior so I probably didn't snug it down all the way. Hasn't happened again.

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post #7 of 83 (permalink) Old 01-05-2017 Thread Starter
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Could this possibly be an Evap system issue? If the tank was overfilled and excess fuel went in to the evap system could this cause these symptoms? Or perhaps a leaky fuel cap. Just not bad enough to cause the CEL to come on yet? I only ask since the issue seems to have happened after refueling.

A while back I was cruisin' about 75mph on the interstate when all of a sudden the engine lost power and then surged a bit and then leveled out. It was almost as if I hit the rev limiter. The CEL light came on. When I made it home I pulled the code which indicated an evap issue. First suggestion was to check the fuel cap, which I did by loosening and then firmly re-tightening it. I had refueled a few days prior so I probably didn't snug it down all the way. Hasn't happened again.
I have filled up the tank a second time since the initial problem began. What else should I check besides the gas cap as far as EVAP goes?

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post #8 of 83 (permalink) Old 01-07-2017 Thread Starter
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Alright guys, I changed the fuel filter. Nothing but clean gas came out of the old one. Car still has problems under acceleration.

I think it would have to be fuel related though since the car runs fine when just cruising or slowly accelerating. Since it has problems during acceleration it makes sense that it isn't receiving enough fuel, correct?

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post #9 of 83 (permalink) Old 01-07-2017
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I would find a way to monitor the fuel pressure since that seems to be the issue and there are no codes coming up. I have read that this issue will arise while driving at a constant highway speed for some distance then the need to accelerate like to pass a vehicle, and the car will hesitate and stumble just long enough to notice then accelerate like nothing was wrong. this issue from what ive read is caused by cavitation or air bubbles around the intake of the fuel pump caused by the vibration of the pump and the gas not moving or in a static state from the constant speed of the car. I have experienced this a few times with my car and just wrote it up to that, but this was at highway speed (80mph on cruise for a while). I'm not sure if the ECM monitors fuel pressure or not. you may have to get a manual gauge. ive been thinking about getting a Bluetooth OBD2 reader and getting the Torque? app. that may help you if you don't have a handheld programmer/tuner to plug in and data log. sorry for the long winded answer. good luck
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post #10 of 83 (permalink) Old 01-07-2017 Thread Starter
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I would find a way to monitor the fuel pressure since that seems to be the issue and there are no codes coming up. I have read that this issue will arise while driving at a constant highway speed for some distance then the need to accelerate like to pass a vehicle, and the car will hesitate and stumble just long enough to notice then accelerate like nothing was wrong. this issue from what ive read is caused by cavitation or air bubbles around the intake of the fuel pump caused by the vibration of the pump and the gas not moving or in a static state from the constant speed of the car. I have experienced this a few times with my car and just wrote it up to that, but this was at highway speed (80mph on cruise for a while). I'm not sure if the ECM monitors fuel pressure or not. you may have to get a manual gauge. ive been thinking about getting a Bluetooth OBD2 reader and getting the Torque? app. that may help you if you don't have a handheld programmer/tuner to plug in and data log. sorry for the long winded answer. good luck
Thank you for your reply!
It is all the time though, not just after cruising for a bit. Pretty much anytime I try to accelerate quickly, from stop, cruising then accelerating or any other time it bogs down like nothing is happening. Could still be what you were saying though.
From what I saw their isn't a place to put a guage into the fuel line, no hookups at all on the fuel rails. Kind of lame really. Oh well.
I do have a handheld tuner, I'll have to see if I can check the fuel pressure with that.

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The first thing I'd suspect from what you've written is bad gasoline. Gas stations find that premium fuel is seldom used by their customers. That station at which you pump gas could have contaminated fuel in it's premium fuel tank. Best to find out the wholesale supplier of fuel for that station, call them, ask them to check the tanks at that station and report back to you.

Other simple things I'd do...throttle body cleaner, MAF sensor cleaner. Either might be the fix, and both cheap to do.
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post #12 of 83 (permalink) Old 01-08-2017 Thread Starter
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I will try gas from another station, it would be awesome if it were something that simple.
I cleaned the maf sensor and throttle body.
But yes, good things to check!

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post #13 of 83 (permalink) Old 01-08-2017 Thread Starter
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Pretty sure it was just bad gas, filled up from a different station and seems much better! Thanks guys!

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post #14 of 83 (permalink) Old 01-11-2017 Thread Starter
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Pretty sure it was just bad gas, filled up from a different station and seems much better! Thanks guys!

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Nevermind, still have the problem! 😔 Lol.

So the latest update:

Tonight, I was going down 95 and once I got up to 80 their was an obvious loss of power, like the engine was struggling to maintain that speed. So I dropped it down to 75 and put cruise control on.

About 30 minutes in, the traction light started coming on and off, then stayed on, and the abs light came on. About 30 seconds later all the dash lights started flickering and long story short I was stranded on the side of the road, and pretty sure I had either a bad battery or alternator.

My buddy came with a battery, we hooked it up, and it started right up.
So, I probably did have a bad battery, and I was excited at first because I thought maybe that was the problem all along. But it isn't, the car still does the weird accelerating thing. I checked the battery with the voltmeter while the car was running and the alternator appears to be working fine.

So, my latest ideas as to what may be wrong, let me know what you guys think!

1. I'm assuming that the alternator is now controlled by the ECU like most modern cars. Is it possible that the ECU is making the alternator do crazy things and causing problems? I had an aerostar once and the ECU had the alternator putting out 18 volts! So, just thinking maybe something similar could be happening that is affecting the rest of the electrical system?

2. Does the car have ignition modules and coils or just coils? Maybe I have a bad coil, ignition module, or spark plug(s). If it were one of these, I don't think it could be completely bad since the car still idles and cruises fine, but maybe there's just a weak spark somewhere due to a failing part?

3. Low fuel pressure. I'm starting to think the problem is more of an electrical thing, but I still will try and look into the fuel pressure. Bad fuel pressure would definitely explain an acceleration problem.

Lastly, I think I may be getting a little bit worse gas mileage, and it seems like the problem more often occurs around 4k rpms and higher. When the problem surfaces, if I didn't push the clutch in and tried to just keep accelerating, basically nothing would happen. I have to push the clutch in, wait a second for the problem to "disappear" then slowly accelerate up to the desired speed.

The problem is not always the loss of power then lurching forward feeling like I said earlier. Now it is more of just like a no power feeling when it occurs during slow acceleration. I don't know what to refer to it as.

I know this is a long post, but thank you very much for those of you trying to help, I really appreciate it! 😊

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With the symptoms you've given and all I've read here on this subject, I'd give the alternator a hard look.
Go to the 2005-2010GT tech home page and click on the search bar. Type in "bad alternator ".


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