CRX HF sputters when warm

Wow. This is crazy. My 1991 HF runs great until 4 minutes of running. Then she sputters until about 2500 rpm. Anything higher and it feels like the powerband kicks in and runs good. It really sputters hard with the a/c. I can give it gas and it accelerates good, but a steady speed and it sputters. I checked everything. Then started replacing things. Here it goes (luckily i have access to a parts car): Plugs, wires, dizzy, TB, computer, fuel pump and filter, O2 sensor, vacuum assy, injectors, IAC. It stills runs the same. I checked the timing and it stays on the mark throughout all rpm's, but when I give it gas quickly it advances, then comes back to the original mark.
Like I said, under 2500 rpm and a load such as a/c or goin up and incline, it sputters, but I punch it and it does better. In other words, when vacuum drops it seems better.
Someone please shed some light on this. Thanks!

Wow, only other thing I can think of would be MAP sensor. Have you disconnected the emissions control thingy behind the dizzy? I had one of those act funny on me. How is cylinder compression on that motor? Do you have any extra loud valve tick?

well, considering that you replaced half the powertrain with (used?) parts, here's a suggestion:
check fuel pressure. unfortunately, your engine may not produce symptoms without load, so, at least, have ac on to load some.
is dizzy a distributor? as ignitor in distributor can do this.

TPS replaced? assume so, as it is likely to be part of TB.

Thanks for the responses. Yea, good point on the used parts, but they weren't all used parts. The used parts were vacuum assy with MAP, EGR, main relay, and computer. They were all in working shape in the parts car. The compression holds within +/- 3 psi through all cylinders and they were all within spec.
Yes, sorry. Dizzy is the distributer. I put another used one on it, then a new one.
What's strange it that it's very responsive for the first few minutes. Then it sputters. I replaced the temp switch also. Purged all air out of the coolant. Something about the temp and rpm's (<2500).
I really appreciate all the help and suggestions!

sometimes the simplest things are the worst to overlook. fuel filter? air filter? PCV? surprisingly, I had mine slightly lose, and simply wiggling it back in place improved how engine works. also, mine was PACKED with crud.

but all i know is if it is temp relevant, it's vacuum or air leak somewhere. metal expends when hot. small cracks get bigger.
start the engine, get a can of carb cleaner, put the straw in, and start bursting shots of cleaner around throttle body and engine head. sort of going in couple inches wide shots. if it chokes after one - you got your problem area.

we had eclipse that had a little devil:evillol: in one of the throttle sensors. did not like humid weather. single wire sensor, and we had to keep wiggling that wire in a contact, or it won't start.

ahm, check fuel pump contacts? and, of course, the devil of all devils - MAIN RELAY?


also:

Car is fully warm, stalls suddenly while driving, then won't restart unless you let cool down for a while
back to Symptoms (http://www.tegger.com/hondafaq/startproblems.html#symptoms)

Honda-specific
(http://www.tegger.com/hondafaq/startproblems.html#ignitionswitch)Ignition switch (http://www.tegger.com/hondafaq/startproblems.html#ignitionswitch)
* Igniter (http://www.tegger.com/hondafaq/startproblems.html#badigniter)
* Coil (http://www.tegger.com/hondafaq/startproblems.html#badcoil)
Loose wire

Generic to all cars
Coil (http://www.tegger.com/hondafaq/startproblems.html#badcoil)
Loose wire

Car starts, runs, but runs poorly with low power and lousy gas mileage.
Smoke or raw-fuel smell may or may not be present
back to Symptoms (http://www.tegger.com/hondafaq/startproblems.html#symptoms)

Honda-specific
Coil (http://www.tegger.com/hondafaq/startproblems.html#badcoil)

Generic to all cars
Coil (http://www.tegger.com/hondafaq/startproblems.html#badcoil)
* Spark plug wires old and leaky (http://www.tegger.com/hondafaq/startproblems.html#leakywires)
* Poor maintenance (http://www.tegger.com/hondafaq/startproblems.html#maintenance), neglect, incorrect servicing (http://www.tegger.com/hondafaq/startproblems.html#maintenance)
* EGR valve stuck open
Timing belt installed incorrectly
Dirty or oil-soaked spark plugs

http://www.tegger.com/hondafaq/startproblems.html#sudden-stall

and the last of them all motherloads of trouble - leaking engine head gasket?

Thanks for all your input guys. Unfortunetly I have tried everything mentioned..... and then some. I even experimented with putting ice on certain areas such as the injectors, alternator, intake etc before the engine warmed up just to see if this might keep the sputter at bay a little longer, but to no avail. I haven't tried my gas cap though, but it does release pressure when I open it. My charcoal canister is the ONLY thing I haven't replaced, but I'm doubtful that it could be my problem. My muffler may need replacing, but my previous rex had a worse muffler and still ran fine. If I remember correctly, this all started after I changed my oil. Same oil as before. I cannot find anywhere in the back part of the engine where (while putting in an oil filter) a wire came loose. This all happened suddenly. Nothing gradual.
One other thing, my light burned out for the "OIL" indicator. Yes it does have pressure, but it doesn't come on at start up anymore. I considered this as being a possibility for the computer not to see resistance during the start up cycle. Sounds strange, but I learned that stranger things can happen. Welcome to my world.
If anyone has any more ideas or revelations, please post these. And thanks!

Thanks for all your input guys. Unfortunetly I have tried everything mentioned..... and then some. I even experimented with putting ice on certain areas such as the injectors, alternator, intake etc before the engine warmed up just to see if this might keep the sputter at bay a little longer, but to no avail. I haven't tried my gas cap though, but it does release pressure when I open it. My charcoal canister is the ONLY thing I haven't replaced, but I'm doubtful that it could be my problem. My muffler may need replacing, but my previous rex had a worse muffler and still ran fine. If I remember correctly, this all started after I changed my oil. Same oil as before. I cannot find anywhere in the back part of the engine where (while putting in an oil filter) a wire came loose. This all happened suddenly. Nothing gradual.
One other thing, my light burned out for the "OIL" indicator. Yes it does have pressure, but it doesn't come on at start up anymore. I considered this as being a possibility for the computer not to see resistance during the start up cycle. Sounds strange, but I learned that stranger things can happen. Welcome to my world.
If anyone has any more ideas or revelations, please post these. And thanks!

It's an HF - clean the EGR system and R&R the cat. They lean burn while cruising, and the heat cokes up the EGR.

PROBLEM SOLVED. i just got done with this repair. There is a thermister (temperature dependent resister) just under the dizzy. looks like a temp sensor but it is not. When it does not work the car does not know that it is warmed up and the injectors continue to deliver large, too large, amounts of fuel that a COLD motor needs. the car sputters because it is getting too much fuel. 35 dollar part, 13 foot pounds of torque, easy to fix but hard to diagnose

The issue could be a bad O2 sensor or clogged fuel filter.