What, other than plugs, wires , cap and rotor would be causing loss of power on acceleration, but not all the time,, intermittently.

Check out the fuel pressure regulator.Youtube has a good description of what is does.I changed mine and have more power now.

Worn bushings in the distributor ?

I have a 1993 Taurus GL V6 3.0L..I"am experiencing a loss of power. Hesitates on acceleration Only when It's cold.When is get hot it runs very good. I have Replace Spark Plugs Cap & rotor were change air filter & fuel filter & TPS/EGR..... & it has a rebuilt ENG in it...this could be a sensor. But which one could it Be?

What Can This Be?

Misfire is a common driveability problem that may or may not be easy to diagnose, depending on the cause. A misfiring cylinder in a four-cylinder engine is, pardon the pun, hard to miss. The loss of 25% of the engine's power output is the equivalent of a horse trying to run on three legs. The engine may shake so badly at idle that it causes vibrations that can be felt in the steering wheel and throughout the vehicle. The engine also may be hard to start and may even stall at idle, depending on the accessory load (air conditioning, headlights and electric rear defroster, for example).

When misfire occurs, performance suffers along with fuel economy, emissions and idle quality. And, when a misfiring vehicle is subjected to an emissions test, it will usually fail because of the unusually high levels of hydrocarbons (HC) in the exhaust.

What causes a cylinder to misfire? Basically, it's one of three things: loss of spark; the air/fuel mixture is too far out of balance to ignite; or loss of compression. Loss of spark includes anything that prevents coil voltage from jumping the electrode gap at the end of the spark plug. Causes include worn, fouled or damaged spark plugs, bad spark plug wires or even a cracked distributor cap. A weak coil or excessive rotor gas inside a distributor would affect all cylinders, not just a single cylinder.

"Lean misfire" can occur when the air/fuel mixture is too lean (not enough gasoline in the mixture) to burn. This can be caused by a dirty, clogged or inoperative fuel injector; air leaks; or low fuel pressure because of a weak pump, restricted filter or leaky pressure regulator. Low fuel pressure would affect all cylinders rather than an individual cylinder, as would most air leaks. A leaky EGR valve can also have the same effect as an air leak.

Loss of compression means the cylinder loses most of its air/fuel mixture before it can be ignited. The most likely causes here are a leaky (burned) exhaust valve or a blown head gasket. If two adjacent cylinders are misfiring, it's likely the head gasket between them has failed. Also, if an engine is overheating or losing coolant, it's likely the head gasket is the culprit.

Intermittent misfires are the worst kind to diagnose because the misfire comes and goes depending on engine load or operating conditions. They seem to occur for no apparent reason. The engine may only misfire and run rough when cold but then smooth out as it warms up. Or, it may start and idle fine but then misfire or hesitate when it comes under load. Also, it may run fine most of the time but suddenly misfire or cut out for no apparent reason. Intermittent misfires can be a real challenge to diagnose, so let's start with a steady misfire in one cylinder before moving on to intermittent misfires.

Hope this help.

could really have a number of problems which are but not limited to timing, fuel restriction, wiring to a sensor O2 or TP ECT sensors or even corrosion in wiring, ignition system (cap, rotor, wires, plugs). exhaust restriction, restricted air intake (air filter). please look at all obvious first and if find something please let me know

Main causes of misfire would be loss of spark; the air/fuel mixture is too far out of balance to ignite; or loss of compression.

Loss of spark includes anything that prevents coil voltage from jumping the electrode gap at the end of the spark plug. Causes include worn, fouled or damaged spark plugs, bad wires or even a cracked distributor cap. A weak coil or excessive rotor gas inside a distributor would affect all cylinders, not just a single cylinder.

"Lean misfire" can occur when the air/fuel mixture is too lean (not enough gasoline in the mixture) to burn. This can be caused by a dirty, clogged or inoperative fuel injector; air leaks; or low fuel pressure because of a weak pump, restricted filter or leaky pressure regulator.

Loss of compression means the cylinder loses most of its air/fuel mixture before it can be ignited. The most likely causes here are a leaky (burned) exhaust valve or a blown head gasket. If two adjacent cylinders are misfiring, it's likely the head gasket between them has failed. Also, if an engine is overheating or losing coolant, it's likely the head gasket is the culprit.

You can isolate the weak cylinder by temporarily disconnecting each of the spark plug wires, one at a time, while the engine is idling. When there's no change in the idle speed, then you have pinpointed the weak cylinder.

Main causes of misfire would be loss of spark; the air/fuel mixture is too far out of balance to ignite; or loss of compression.

Loss of spark includes anything that prevents coil voltage from jumping the electrode gap at the end of the spark plug. Causes include worn, fouled or damaged spark plugs, bad wires or even a cracked distributor cap. A weak coil or excessive rotor gas inside a distributor would affect all cylinders, not just a single cylinder.

"Lean misfire" can occur when the air/fuel mixture is too lean (not enough gasoline in the mixture) to burn. This can be caused by a dirty, clogged or inoperative fuel injector; air leaks; or low fuel pressure because of a weak pump, restricted filter or leaky pressure regulator.

Loss of compression means the cylinder loses most of its air/fuel mixture before it can be ignited. The most likely causes here are a leaky (burned) exhaust valve or a blown head gasket. If two adjacent cylinders are misfiring, it's likely the head gasket between them has failed. Also, if an engine is overheating or losing coolant, it's likely the head gasket is the culprit.

You can isolate the weak cylinder by temporarily disconnecting each of the spark plug wires, one at a time, while the engine is idling. When there's no change in the idle speed, then you have pinpointed the weak cylinder.

Does the car always hesitate during acceleration? If it ALWAYS struggles when it starts or ALWAYS hesitates on acceleration then I would say the issue is fuel delivery. If the problems are more intermittent and come-and-go then it could be an electrical issue.

I would start by changing the fuel filter. Changing plugs, wires, cap, and rotor are all good things to do as your budget will allow. I doubt you will have to change your injectors.

If you end up replacing any rubber fuel line, be sure to use the high-pressure stuff made for use on fuel injected cars.

I hope this helps! -Nick

Do you know how check if every cilinder is working? with the engine in idle, go to the distribuitor cap and carefully unplug one at the time, every cilinder spark plug wire,in the cilinder you dont see a diference in rpm variation, that cilinder is not working, replace spark plug, if you see spark jumping fron the distribuitor cap torch the spark plug wire, another cause to a cilinder fail could be a loss of compression in one or more cilinder

Have you had your fuel pressure tested?