Fox Fuel or spark issues?

[Frank cortez]

I have 1991 mustang that got rebuilt and added a cam
Mechanic just said it was stage 2 cam thats all but anyway Ive recently been having an issue where sometimes after turning engine off it won't turn back on and will act as if there no gas but if i disconnect fuel pump it'll turn on normally and die since fuel pump is unplugged
Today April 3 2025 that happened at work and found out my mass sensor connector might've been lose or wires might be going bad since after that it ran fine

Also iac is disconnected since it revs to 3k Rpm when connected and car also loses power after driving for a while and starts bogging down and back fires from driving from a stop

could my mass sensor be causing all this?

Code connector is nowhere to be found so so cant get codes..

 

[AeroCoupe]

Diagnostic port should be over on the driver side in front of the brake booster and between the master cylinder and the inner fender. It’s there you just need to find it as without checking for codes you are chasing your tail.

 

[General karthief]

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...

www.stangnet.com

you can see were the diagnostic plug is here:

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

@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...

www.stangnet.com

 

[Frank cortez]

Diagnostic port should be over on the driver side in front of the brake booster and between the master cylinder and the inner fender. It’s there you just need to find it as without checking for codes you are chasing your tail.

Yes i know where the connection is at but the wires aren't the correct ones seems that someone just put random wires to fill in the connection

 

[Noobz347]

Yes i know where the connection is at but the wires aren't the correct ones seems that someone just put random wires to fill in the connection

You need to get that sorted out then. Like mentioned, you're just shooting in the dark.

 

[AeroCoupe]

If it were me I would get the EVTM and pull the harness out of the car and go through it if the whole thing is like this.

I realize that may not be practical but chasing one or two wires in the car is one thing.