My 1999 lincoln has had the top thermostat housing changed the whole top of the motor cadalac converts cut off new fuel pump new fuel filter replaced injector spark plugs Im really ready to give up: and when Im driving it after all this that has been fixed it still ends up running slow i have to press the gas pedal all the way to the floor to start it or drive it. its giving me a headache, please suggestion are need im spending a lot of money

Small wonder you are confused. The possibilitiess are so complex it would require a professional mechanic to narrow the diagnosis down. Here is a very long list of what might have to be checked otherwise.

Regarding the thermostat housing, its removal could impact engine temperature regulation. Running the fan continuously helps, but the underlying issue persists.

Step by step:

Fuel Delivery Issues:
Ensure that there's sufficient fuel reaching the engine. Check the fuel pump, fuel filter, and fuel lines for any blockages or leaks.
If the fuel system is compromised, it can lead to power loss and stalling.

Ignition System Problems:
Verify the condition of ignition components: spark plugs, ignition coil, distributor, and spark plug wires.
Faulty ignition parts can cause intermittent power loss and starting issues.

Electrical Connections and Wiring:
Inspect all electrical connections related to the ignition system, including ground connections.
Loose or damaged wires can disrupt the electrical flow and affect engine performance.

Air Intake and Air Filter:
A clogged air filter restricts airflow to the engine, leading to poor performance.
Check and replace the air filter if necessary.

Throttle Position Sensor (TPS):
The TPS monitors throttle position and communicates with the engine control unit (ECU).
A malfunctioning TPS can cause power loss and stalling.

Idle Air Control Valve (IACV):
The IACV regulates idle speed. If it's faulty, the engine may stall or struggle to start.
Clean or replace the IACV as needed.

Vacuum Leaks:
Inspect vacuum hoses, gaskets, and the intake manifold for leaks.
Vacuum leaks disrupt the air-fuel mixture and affect engine performance.

Faulty Sensors:
Modern engines rely on various sensors (e.g., crankshaft position sensor, camshaft position sensor) for smooth operation.
Use an OBD-II scanner to check for error codes related to sensors.

Compression Issues:
Low compression in one or more cylinders can cause power loss and starting problems.
Perform a compression test to check cylinder pressures.

Starter Motor and Battery:
Ensure the starter motor engages properly and turns the engine over.
Test the battery voltage and connections.

Exhaust System:
A blocked or damaged exhaust system affects engine performance.
Inspect the exhaust manifold, catalytic converter, and muffler.

Engine Control Module (ECM):
If other checks don't reveal the issue, consider examining the ECM for faults.

Sounds like you have a vacuum leak that gets worse when motor has load on it

Water pump is in the middle of the motor on the passenger side of a front wheel drive (big pulley beside alternator). The thermostat should be at the driver side of motor ( follow the top hose from the radiator to the connection at motor) that will be the thermostat housing!

Check again piece by piece all that you just replaced to make sure one of then is not faulty from that house.
Check the oxygen sensors
The engine PCM
Catalytic convertor

Wish you luck

Have you checked the fuel pressure at the motor with a gauge ?

You also should check volume & know if your loosing fuel when
it shuts off,not an easy thing to do

You have an older less complicated OBD1 System, so the data
we have on newer OBD2 (1996 on) actually would help

If you want to spend the money ,you could have a scope put on the
pump motor to confirm it is worn out

The Exhaust Converter question is easy

They last 12 to 14 years & then you just replace it,
but only after you look at fuel trim & do the O2 Sensors,
so you have no rich condition that would ruin the new converters

Lift the car and secure it on a jack stand. Next to the Oil Filter is the thermostat Housing. Remove the oil filter and catch the oil that escapes. Dispose of the oil properly. Drain the cooling system.unscrew the 1"clamp from the heater hose or cut it to replace it with new 3/4" heater hose before you are done (About 3"-measure it first before cutting).Use lube to re-assemble)
Unbolt the goose neck from the block (2 to 3 10mm blots) (Yes, it IS tight in there but hey, you're the one that bought the Chrysler) Remove the old thermostat noting where the top of the thermostat is when taking it out. There should be a U shaped notch near the top that aligns the stat to the housing. Bolt it back in WITH A NEW GASKET. Installation in reverse of disassembly. GO!

I changed the fuel pump on my 2000 LS a few years ago. The system is kinda odd. The actual electric fuel pump is in the tank on the right side. The tank is directly below the rear seat. If you remove the seat bottom you will find a 6 inch or so cover. Under the cover there is a plastic, threaded collar that locks the fuel pump into the tank. The driver's side also has a pump, but it works only my venturi effect from the electric pump on the other side. This pump is used to equalize the fuel level from left to right. The drive shaft tunnel prevents all but the very top of the tank from communicating left to right. Also, I would go with a factory pump. It comes with the whole pump, connectors, filter, Pickup, etc. I tried a parts house pump at first. It was only $50 less and only came with the motor.

I had the same problem with a Corolla, and it was fixed by cleaning the fuel filter ( attached to the pump ), the fuel filter was clogged and could not supply enough fuel to the pump. Hope you fuel pump is good. Best of luck

check the spark plugs to see if they are getting any spark-pull one of the plugs, reconnect the wire, and hold near something metal on the car while someone turns the engine over-if no spark-it's electrical-maybe just the plugs-maybe something more serious

Follow the Upper Radiator Hose to the Motor. Remove the Bell Housing that the Hose attaches to and Change the Thermostat that is Underneath this Bellhousing. Should take care of your Problem. Please Rate my Response, I need all the Help That I can Get! Thanks!