88 speed density misfire and bucking

kush · May 29, 2026

Hey guys, recently I've been dealing with an intermittent bucking at around 3000rpm that I'm pretty sure is a fuel-related issue. I've also noticed this chirping sound at idle. It's also audible until around 2000rpm. I hear it during acceleration and coasting. On wot and anything above 2000rpm, I can't hear it. At idle, it sounds like it's coming from the #3 or #4 injector. Fuel pressure is good. It's got a new regulator and fuel filter. I have videos of it running, but the files are too large to post here. Thanks!

Noobz347 · May 29, 2026

Electrical Thread 'How To Pull Codes From EEC-IV In 86- 95 5.0 Mustangs'

Jan 27, 2016

@Noobz347 - The code dump procedure isn't in the sticky - you may want to add it...

Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for...

Blown88GT · May 30, 2026

It's probably the fuel pump. Fuel pressure can be good at idle, but not under load. Attach a fuel pressure gauge to the Schrader valve with a long hose, zip- tie it to the wiper blade so you can see it from the driver's seat, close the hood & go for a rip. You will probably see the gauge drop to 0 for a second & then come back.

kush · May 30, 2026

Noobz347 said:
[EMBED content="post-8947967"

Koeo codes 11
Koer 44/94. I ran it three times using an innova obd1 code reader and one of the times it threw a 45. Of those 3 times I ran codes, 1 time it said 4 for number of cylinders, another time 6 and one time it didn't give any reading at all.

All my emissions are deleted and the ports in the back of the heads are blocked with plugs from LMR, so 94/44 are expected.

kush · May 30, 2026

Blown88GT said:
It's probably the fuel pump. Fuel pressure can be good at idle, but not under load. Attach a fuel pressure gauge to the Schrader valve with a long hose, zip- tie it to the wiper blade so you can see it from the driver's seat, close the hood & go for a rip. You will probably see the gauge drop to 0 for a second & then come back.

Fp at idle is steady at around 39psi. Good call on reading it while driving, never thought of that; I'll give that a shot and report back.

I know videos would help a ton. I'll try to get them up on YouTube and post the links here.

kush · May 30, 2026

View: https://youtube.com/shorts/rIw6ZAETaHg?si=NawPJERnzYeVptLG

kush · May 30, 2026

View: https://youtu.be/ftnNLJYljhM?feature=shared

2000xp8 · Jun 5, 2026

I'm always skeptical about calling a miss a fuel problem.
I've seen bad injectors before, but you could hear the engine tone change at idle.
I've not heard of injectors chirping, to me that sounds like the belt in the video.
I'd remove the belt and run the car and see if it still chirps.

Mindseye007 · Jun 8, 2026

2000xp8 said:
I'm always skeptical about calling a miss a fuel problem.
I've seen bad injectors before, but you could hear the engine tone change at idle.
I've not heard of injectors chirping, to me that sounds like the belt in the video.
I'd remove the belt and run the car and see if it still chirps.

Sounds like tensioner/idler pulley...

DadLife0724 · Jun 8, 2026

kush said:
View: https://youtu.be/ftnNLJYljhM?feature=shared

Get a hose or piece of pipe, put one end to your ear and move the other end around in that engine bay. When you get close to the chirp it will get louder. That should help you pin point it. Or at least get you close.

88 speed density misfire and bucking

kush

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