acceleration problem

Do you have a check engine light?

Could be caused by one of the following below

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Knock sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard it and keep testing.

I hope my question was clear, but it isn't miss firing on hard acceleration it "gets quiet as if I took my foot off the accelerator and does not pick up any speed" but when I lightly press it will gradually pick up speed and change gear. Just put in plugs, cap and rotor less than 2 months ago, after a winter storage. It does not have a catalytic converter any longer, so I will start from your list and go from there.

And if I "gun" accelerator in park or neutral it picks up speed just fine.

And no "check engine light"

Check the catalytic converter. No acceleration problems when in Park or Neutral, with problems under load usually indicate a plugged catalytic.
Go to a parts tore and pick up a cheap bypass pipe and insert it in line in place of the converter. Then drive it. I'm guessing you'll see you acceleration come back.

SAID HE AIN'T GOT ONE!

HOW MANYS ON THERE ANYWAY?

DOES HE MAYBE HAVE STORED CODES?

THE MEDIC

Ahh, I missed that part. It could be a plugged muffler then. 9 out of 10 times, loss of acceleration under load is that the engine is unable to breathe freely.
Also check fuel filter and fuel pressure. Make sure the fuel system is clean. Make sure the timing is set correctly. While checking the timing, make sure it advances properly under acceleration. Also, make sure the timing is rock steady at idle. If it isn't, you have a timing chain issue.

Use some carb cleaner to check for vacuum leaks.

No codes, or CEL.... did the "koeo and koer" tests to retrieve codes which came up "11" (nothings wrong), and yes I did say I have taken off both converters years ago. Checking fuel is my next option.

What sort of back pressure are you looking at in your exhaust system? Are you completely sure it's flowing the way it's supposed to?

I have a 1992 mustang lx with a 2.3 engine. Same problen, engine bog's down, no acceration. New wires,plugs, new ingnition core,same problem, heat mark under car by converter, cut converter pipe. Ran good at the start, then bogged down again, other converter cherry red. Help! About ready to send to junk yard.

Check to make sure it isn't running too lean. Did you also remove the oxygen sensor? Check for vacuum leaks. Check the throttle position sensor with a multimeter to make sure it is reading smoothly across its operating range.

Thanks fellas I appreciate all the suggestions. But I fixed the problem about a month ago. It wasn't motor related. It was the Throttle kickdown cable. The linkage has a plastic bushing that was busted so the cable was loose causing it not "kickdown" the tranny shifts properly. It would change gears but gradually. Here is the place I found it : http://www.latemodelrestoration.com/item/LRS-4170803/84-93-Mustang-AOD-TV-Cable-Bushing

Thanks for letting us know.

My problem is similar but when i push on the gas pedal in park or neutral, the vehicle will not accelerate and begins to stall out and backfires with a popping noise. The same thing happens when at stop signs and going up hills it has a hard time climbing the hill. 1992 mustang 4 cylinder. changes plugs, map sensor, wires, cleaned the throttle etc. Any ideas?

Check to see if the catalytic converter is clogged, gwell123. Also check for vacuum leaks.