Don’t pass 3k rpm

[Jonatan Issa]

Hello guys!!
I have a Mustang 1993 the car is full stock. Lately when you are full at throttle the car don’t pass 3k rpm and loose power like it don’t have fuel. When you are cruising the car runs perfect, is a AOD btw. If need more information feel free to ask
My first language isn’t English sorry

 

[General karthief]

Changed the fuel filter recently?
Also check fuel pressure.

 

[Trogdor]

Does the engine feel like it breaks up, or just no power?

 

[Jonatan Issa]

Yep the fuel filter was change like 2 weeks ago

 

[Jonatan Issa]

Does the engine feel like it breaks up, or just no power?

It feels like it has no power, but if you leave it down it grabs a little power

 

[Trogdor]

Do you have a timing light?

 

[Jonatan Issa]

Do you have a timing light?

No :/

 

[Jonatan Issa]

Do you have a timing light?

It could be the MAF?

 

[Trogdor]

I was going to ask you to check to see what the timing did while revving the engine up with the SPOUT connected.

 

[General karthief]

Probably not the MAF, the computer would show a code for that, have you checked for codes? There can be codes without the CEL coming on.
You need to be methodical when these cars act up. This will show a step by step procedure for resolving idle, stall and surging issues:

Help me create the "Surging Idle Checklist"

Updated 05 July 2022 to add rough idle when cold and smooth idle when up to normal operating temperature. See the EGR tech information, section #15 for more help. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank...

www.stangnet.com

 

[AeroCoupe]

You really need to check for codes as mentioned above:

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...

stangnet.com

Does it just not go past 3,000 rpm? Can you slowly press the gas pedal and the rpm's go up or will it just not go past 3,000 rpm?

When checking the fuel pressure you need to set it to 39 psig with the vacuum line disconnected from the fuel pressure regulator (FPR) and the vacuum line plugged. When you reconnect the vaccum line to the FPR the pressure will drop as this is normal. When the rpms go up the fuel pressure will rise but will not go past 39 psig. If the fuel pressure does not rise then you have a fuel issue.

You replaced the fuel filter but how old are the air filter, cap, rotor, plug wires, and plugs? These need to be inspected and if needed replaced. Do not buy into the whole platinum spark plug thing with these cars. Just run a Motorcraft 3924 and they work very well. I would get a Motorcraft cap (part number DH411B), rotor (part number DR374B), and 8mm stock plug wires (part number WR4017C). If the car still has the factory air box then the part number for the Motorcraft air filter is FA1042. You can get all of this at www.rockauto.com for a decent price but some local auto parts stores may carry them or can get them in a day or two.

If you want to get the 9mm Ford Performance plug wires (most of us run these) the part number on the plug wires will vary due to color of the plug wire:

Black - M-12259-M301
Red - M-12259-R301
Blue - M-12259-C301

So a general tune up on these cars is air filter, fuel filter, cap, rotor, plug wires, and plugs. You may need to do a base idle reset which should be covered in the thread the General posted.

Again, first thing you need to do is check for codes.

 

[Mustang5L5]

A faulty ignition coil would also present this same symptom, with no codes generated.

My car had this exact issue. Ended up being the coil

 

[Jonatan Issa]

You really need to check for codes as mentioned above:

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...

stangnet.com

Does it just not go past 3,000 rpm? Can you slowly press the gas pedal and the rpm's go up or will it just not go past 3,000 rpm?

When checking the fuel pressure you need to set it to 39 psig with the vacuum line disconnected from the fuel pressure regulator (FPR) and the vacuum line plugged. When you reconnect the vaccum line to the FPR the pressure will drop as this is normal. When the rpms go up the fuel pressure will rise but will not go past 39 psig. If the fuel pressure does not rise then you have a fuel issue.

You replaced the fuel filter but how old are the air filter, cap, rotor, plug wires, and plugs? These need to be inspected and if needed replaced. Do not buy into the whole platinum spark plug thing with these cars. Just run a Motorcraft 3924 and they work very well. I would get a Motorcraft cap (part number DH411B), rotor (part number DR374B), and 8mm stock plug wires (part number WR4017C). If the car still has the factory air box then the part number for the Motorcraft air filter is FA1042. You can get all of this at www.rockauto.com for a decent price but some local auto parts stores may carry them or can get them in a day or two.

If you want to get the 9mm Ford Performance plug wires (most of us run these) the part number on the plug wires will vary due to color of the plug wire:

Black - M-12259-M301
Red - M-12259-R301
Blue - M-12259-C301

So a general tune up on these cars is air filter, fuel filter, cap, rotor, plug wires, and plugs. You may need to do a base idle reset which should be covered in the thread the General posted.

Again, first thing you need to do is check for codes.

Ok gonna check for codes, for your question the car can pass the 3k rpm but struggling in wot, in park he rev perfect is just when you are cruising and floor it

 

[AeroCoupe]

So this is when the motor is under load. My bet is it’s ignition related.

 

[General karthief]

I like the coil breakdown reasoning, and don't go for an aftermarket like Accell, stock motorcraft if you can.

 

[Jonatan Issa]

I like the coil breakdown reasoning, and don't go for an aftermarket like Accell, stock motorcraft if you can.

Ok today gonna change the spark plugs I bet it have the 30 yr old one if not I’m gonna buy that!

 

[Bullitt347]

Have you changed the dist cap and rotor lately?
If so, are they the right parts?

 

[Jonatan Issa]

Have you changed the dist cap and rotor lately?
If so, are they the right parts?

Nop still stock

 

[Jonatan Issa]

I like the coil breakdown reasoning, and don't go for an aftermarket like Accell, stock motorcraft if you can.

I don’t know if this helps but the car only do it when is in normal temp when the car is cold don’t do anything

 

[General karthief]

Ok, without getting into thermodynamics the down and dirty explanation is from ambient temperature to operating temperature can and does effect coil efficiency. As it does anything that carries electricity like plug wires, bad connections and old brittle wires.