The Dreaded Mustang Acceleration Hesitation...

Thump1t

New Member
Jun 6, 2016
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2000 Mustang Base Model 3.8L V6, 5 speed tranny. The only "Engine Mod" I've done was install a K&N Cold Air Intake

As I noticed while searching the forums before posting, seems like quite a few people have had this issue during acceleration. Since all of them were pretty much different repairs in the end, I figured I'd give it a shot too.

Since I purchased the car quite a few years ago, used with 30k miles on it, it's always had a hesitation/gurgle during an idle.

Now, having almost 130k on it, it's still doing it, but now it's getting increasingly worse, you can literally hear the MAF do it's job...and it scares the :poo: outta me, lol. Nothing like a loud "THUD" from it to get the engine back to RPM. Also happening at low RPM during acceleration, mainly between 1500-2000 rpm. At cruising speed of 75 @ roughly 2100 rpm, sometimes I can feel a slight hesitation that feels not much different than a gust of wind hitting the car. If I floor it from cruising speed, it'll hesitate a few times until I get around 3k and run just fine.

So here is what I've done recently:
New fuel pump w/socks and inline fuel filter less than 1 year ago
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New Plugs/wires less than 1 year ago
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Today, installed a new Absolute Pressure Sensor, most would call it the new equivalent to a fuel pressure regulator, which didn't fix the issue, it was a shot in the dark.

While I had the car in the shop today, I had a concern with the fuel pressure. At a prime, no start, it's @ 40psi. At an idle, it's between 25-30 on a guage, reading it from my scanner, the ECM is reading it at roughly 32psi. I felt this to be a concerning pressure drop, but I have no glue, as I'm not much of an engine guy. Fuel pressure seems good at start, could I have an open injector? Scanner isn't reading any faults with them during my drive test, but if it's stuck open, maybe it won't show an issue?

Coilpacks, would there not be a Code showing a misfire if a coilpack was bad? It does when I have a bad plug or a wire, so why not a coilpack?

What do you guys/gals think?

I took some pictures, quite a few actually, of some scanner screens (cylinder contribution, OS21, OS11, OS..blabla etc.) if there are any ASE guys on here that know what the hell they mean. I'll attach them if anyone is interested.

Please help get my baby back to normal, I miss playing around :)
 
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