Hesitation
 

Well, as you may know, I just got a 2002 GT 5 speed. I noticed that when I am at low RPMs in 3rd or 4th (around 1000-2000 RPM) and i hit the gas, it can have a tendency to be a little rough. Feels like its a little jumpy but then it catches on and goes. Does anyone have an idea to what this could be?

hesitation
 

Have you checked the plugs and cables? I just did a PI swap and am having a similar situation. I actually think mine is a low octane level but I am going to change my plugs anyway even though they are only 10k miles old. That always seems to be the first thing to check. Good luck.

what speed are you going?

if it revs up a little before it starts to accellerate, it might be your clutch slipping.

Sounds electrical. I bet you are getting a missfire due to a bad COP (Coil Pack). They sit right on top of the spark plugs.

Assuming you have just one bad one, you could get a new one, or borrow one off another Mustang, and try it on each cyclinder and then drive the car. I bet the problem goes away. It is very time consuming.

One would think you would get an SES triggered with a missfire, but you often times won't with a bad COP. I had a similar problem last year and never got a code and I know of other examples too. Tecnicians get confused because they dont see the code.

A plugged fuel filter could also cause what you are describing.

If you have over 40k miles on the car w/o changing the fuel filter, I would get more suspicious. But I bet you $5 it is the COP.

There is another trick you can try. It just might work and only takes a few minutes.

With the car running and the hood open, take a large flat head screw driver and place the tip on top of a fuel injector. Place your ear on the handle. You can actually hear the injector pulsing. It will make a tapping sound. As you rev the engine, the tapping frequency will increase. If you have a missfire, you may be able to hear the tapping get dicked up on the bad cylinder. If you do, then you found the bad COP. HOWEVER, if the injector does not know that the COP is not firing right, the injector will still pulse normally and you won't be able to tell the difference.

Well, it happens at low speeds, and RPM below 2k. I am kind of thinking it is an electrical problem as well, and I know it isn't the clutch slipping, although I had thought that at first as well. It does have 76k miles on it, and as far as I know, the stock fuel filter, so that may be the problem. No SES light has come on so far. I don't think it is detonation, because I usually run 88 or 91 octane in it (I don't trust the 86 octane that they have out here.) It KIND of feels like a misfire, but it seems as though the car would be misfiring through the entire RPM range? and I know that I don't have a loss of power in there. I recently replaced the air filter as well (k&n of course). I think I'll try testing the coil packs, and replace the fuel filter, and see how it goes from there!

Also a guy at work said that it may be a vacuum line that has come loose, but he drives an old Trans Am 305 and is upset he can't stay anywhere near me :-)

The fact that it happens at low rpms leads me to think a fuel filter or coil pack. As the coil pack gets worse, the missfires will get into the higher rpm range. They seem to start low and then spread out across the entire rpm range.

If you have nearly 80k on a fuel filter, you should replace that anyway. I would start there.

Thank you! I was probably gonna do that tomorrow!

And on a side note, I just got offered a ROCKIN deal on a vortech kit which I am PROBABLY gonna have to take up... man o man am I excited!