Progress Thread 2000 Mustang Gt Poor Acceleration And Performance

Polyetrix85

New Member
Jun 15, 2016
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Hi guys, I own a 2000 mustang gt. I bought this car at the beginning of Feb. 2017. Ever since I've had the car I thought it felt a little off. Not full "power" and acceleration. I thought I'd do a tune up and see where I got being that the previous owners might've not did any maintenance. Long story short. My cars performance is kind of bogged. It feels like it's just not pulling as hard as it should. The throttle response isn't instant, or very close to instant. My friends Mustang, a 96 with a 02 swapped engine, his throttle response is about dead instant. For mine, It's like you can hear the air rush in, and then half a millisecond you can hear the engine detonate and the exhaust. Lower RPM pulls are trash. Until it starts hitting like 3,500 rpms and up it'll start to pull kind of hard. But even still it feels bogged. It feels like it's not getting enough fuel as well if I had to guess. Although I've never had a issue to know exactly. I do have some mods on it; SR Performance 70mm throttle body/upper intake plenum. A Airaid cold air intake set up. Full exhaust (stock manifold/exhaust) I just had the CATS deleted and a pipe welded in place. No, this is not the cause of my problem, as none of my mods are. This issue of mine was before anything was done to it. None of my mods made this really worse either, it just feels like something is off. I've replaced the fuel filter, fuel pump, spark plugs, COPS (coil on plugs), I've ran fuel injector cleaner for like a month. New TPS. I did not replace the MAF, but I did have a bbk new MAF I put on it, and it didn't change anything so the MAF was working. I replaced the fuel pump because when I checked the fuel pressure, it was at 28 psi idle. It took 2 1/2 minutes to reach that psi. I haven't checked the fuel pressure after replacing the fuel pump yet, but I will. As far as more information, there is a strange hissing noise that sounds like it's coming from my driver's side front wheel. I don't know exactly where at, but I will link some videos if anyone could help me with what it is. Maybe a exhaust leak or something? Idk if that would cause my low performance or not. As well as my exhaust sounds like it sucks in the "sound", or sucking in air once u hit a rpm. The exhaust sounds "airy" to me. Like the tone/sound kind of dissipates. It's always done that before I had the exhaust done, and I thought it was weird. I'll get a video of that and get anyone's opinion on it. No check engine light is on, so no codes. This is a long thread, I do apologize. I've been trying to figure this out for awhile, and would really appreciate any help, thanks!
Videos:
View: https://www.youtube.com/watch?v=88725WQuI8E&feature=youtu.be



View: https://www.youtube.com/watch?v=MH_4GfgaEw0&feature=youtu.be
 
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robertsa

Well-Known Member
Apr 22, 2017
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San Antonio
Start looking for a vacuum leak. Check your fuel pressure again, since you said you never verified anything changed after swapping pumps.

And most importantly, stop part swapping and start troubleshooting.
 

Polyetrix85

New Member
Jun 15, 2016
15
1
1
27
Start looking for a vacuum leak. Check your fuel pressure again, since you said you never verified anything changed after swapping pumps.

And most importantly, stop part swapping and start troubleshooting.
Thanks I'll do so. I have checked for a vacuum leak twice and haven't came up with anything. Could a bad IAC valve be my issue? I hear they are notorious for mustangs and their problems.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,890
519
204
Houston Texas
To me the 2nd clip sounds like a worn front accessory bearing. Try disconnecting the front accessory drive belt to see if the noise changes. Using a mechanic's stethoscope is also a good way to locate bad bearings.

Consider that the larger throttle body "could" be one source of the poor throttle response. That's the "dirty little secret" of some modified parts. The air flow gets "lazy" at low flow rates when going through large openings.

Suggestion before changing anything. Have the alternator tested for excessive AC ripple (bad diode) and correct output. No excuse to skip this step as almost all autoparts stores will test for free. Use that mechanic's stethoscope on the alternator to make sure it's not the alternator bearing making noise.
 
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Polyetrix85

New Member
Jun 15, 2016
15
1
1
27
To me the 2nd clip sounds like a worn front ACC bearing. Try disconnecting the front ACC drive belt to see if the noise changes. Using a mechanic stethoscope is also a good way to locate bad bearings.

Consider that the larger throttle body "could" be one source of the poor throttle response. That's the "dirty little secrete" of some modified parts. The air flow gets "lazy" at low flow rates when going through large openings.

Suggestion before changing anything. Have the alternator tested for excessive AC ripple (bad diode) and correct output. No excuse to skip this step as almost all autoparts stores will test for free. Use that mechanic stethoscope on the alternator to make sure it's not the alternator bearing making noise.
 

Polyetrix85

New Member
Jun 15, 2016
15
1
1
27
I forgot to mention that the alternator has been replaced. My alternator actually makes a different noise. It whirrs. Idk what it is. But seems to be holding the correct charge. I'll get it tested to be sure as you're correct. No excuse. As far as the throttle body. I did put the stock one back on to see if it helped and it didn't. If anything it just felt restricting. Same low performance.