During a ride ithe car shows low rpm it hesitates and almost is turning off it. i have changed the MAF and Cathalyst. The computer doesn not register any code.

system too rich bank one I think you will have to replace one of your oxygen sensors

What you do is Google the codes & read up on them

Type: 2004 Monte Carlo OBD POO68 etc

I would guess when you say you need help you,
don't have the years of experience & test equip
to work on it anyway

A faulty throttle position sensor or an intake air leak near the mass air flow sensor.

A combination of problems could be causing your hesitation/stall issue:

1. Bad MAF (Mass Air Flow) sensor
2. Bad TPS (Throttle Position Sensor)

Getting a free diagnostic test to pull codes will make narrowing down your problem a bit easier. Most chain auto parts stores will do a complimentary diagnostic test. The most common cause with a car that stalls when warm is the TPS. It controls your idling speed under all conditions. Even replacing the MAF alone doesn't always fix the problem although it may show up as being problematic. The 2 parts basically go hand in hand with your particular problem.

Hello,
When the MAF on most vehicles reach a point of preventing the engine from starting, you can usually just unplug it and the engine will start. If that doesn't work-
You may want to try having the O2 sensor, ( Oxygen sensor ), checked. It works with other components of the emission system and can cause similar symptoms as the MAF, including preventing the engine from starting.

Donnie

looks like not enough fuel pressure, check the fuel filter.
and the fuel pump pressure.with car running 60 psi
the pump is located at the rear seat driver side you have to remove the carpet to access the cover. if the fuel pressure checked "OK" suspect defective maf sensor (sometimes defective maf sensor do not show errors codes)another way to test is disconecting the maf sensor and start the car (computer goes to limp in mode) and works little better,or check by scanner idle= low grams per seconds and increase when accelerate.

If you own a 2004, 2005, 2006 or 2007 Toyota Corolla and your car hesitates when you accelerate or it hesitates when driving, you should try the solution described here. Below is a list of the behavior your car may show that tells that you should try this procedure before going to a mechanic or repair shop.

• The accelerator is slightly pressed while the car is running and it slightly jitters or hesitates
• After completely stopping the car (a red light for example), it hesitates when you accelerate to continue driving
• Engine power is below the usual level
• Sometimes check engine light turns on

You should know that while those problems can be caused by several issues, including low quality or altered fuel or even a loosely tighten fuel cap, the most common cause is a dirty MAF flow meter sensor.
The MAF sensor (Mass Air Flow Meter Sensor) is in charge of detecting how much air (in mass, not volume) is coming in to the engine, so the ecm computer can calculate the amount of fuel to be injected.
Some times this sensor gets contaminated by lots of microscopic debris that scape the air filter and accumulate on its sensing parts over time. The resulting effect is that the MAF flow meter sensor gets less "sensible" and detects less air than it is currently entering the engine. The reaction of the ecm computer will be to inject less fuel to keep the air fuel balance, taking as reference the false reading of the MAF flow meter sensor. This will produce a too-lean mixture, which is responsible of the hesitation, the loss in power and the check engine light.
If your car engine, besides the hesitation, is also producing knocking or engine pinging at high loads, like when going up through a hill, it is attributed to this too-lean condition.
Before going to an auto parts store or to a mechanic to fix the problem, you should try fixing it your self. If the problem is a dirty MAF flow meter sensor, the solution is to clean it, plain and simple. That may save you some money that a mechanic will charge for cleaning it (you could do the same) or for replacing the part when most of the times it is not damaged, just dirty or contaminated

If you were driving a voyager I'd suspect the fuel pump is starting to fail.

Air and fuel mixture incorrect, restart the computer. Disconnect the negative or ground from the battery, turn the lights on to drain the computer faster, wait five minutes then reconnect. The computer is set to work with an old clogged filter, now you have more air coming in due to the K&N. The p0174 is the O2 sensor picking up on this, too much oxigen. Too much oxygen or not enough fuel. If restarting the computer does not work, replace the fuel filter and pressure regulator then restart the computer. You'll have to drive around for the computer to set, during this time do not mess with anything you'll throw off the computer. There should be some information in your vehicles manual about the relearn period. Before anything ceck for vacuum leaks, if there is air entering the engine after the MAF sensor the computer can not mesure it. Check for loose, disconnected or cracked vacuum hoses and replace if necessary. Start from there and let me know.

change the fuel you are using. try some fuel system cleaner. this is a petty issue, every vehicle develops issues over time.a bmw owner complains about hestitations, a bmw driver enjoys the ride. DEAL WITH IT!!!