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Amedee, Former ASE Master Tech
Category: Car
Satisfied Customers: 25814
Experience:  ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector
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automatic..temperature gage..o2 sensor..catalytic converter..coil pack

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damn problem with my eagle talon non turbo 2.0L 420A engine automatic transmition...when i ran it about 10 minute the engine start bucking the rpm needle act crazy and then the car stop,then i stop and start it back and rpm is going 4000 to 1000 rpm like if i press the gas en release it few time, then stop again,i let the car cool down (the temperature gage is normal)for a while and then it is ok and can drive it for about 10 minute again and the its start bucking again and then stop...whats the probleme,the only code i get is,EGR valve,and my o2 sensor cause my catalytic converter is remove(i bought a new one cause i bought the car without it), i tried to unpluged egr valve an ran it without it to see, but it did it even without it i also change spark effect,i dont know if its a missfire,my coil pack look in great shape when car is start i unplug spark plug wire one by one and it work fine,someone have an idea whats my problem??

You might have an air or a vacuum leak. This is very common! Open the hood and listen for a hissing sound when the engine is running.
Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor that is not reading airflow accurately, an EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow.
If it is hard to pinpoint take some brake cleaner or starting fluid around the intake manifold and vacuum lines and see if the engine stumbles or if the idle is affected. Be extremely careful when doing this!

Also, your throttle body may be carboned up and need to be cleaned! This can cause all sorts of idle and hesitation problems. This is caused by the throttle plate not seating properly. The First thing i would do is clean out the throttle body with some throttle plate and intake cleaner and a small brush. Another common cause would be the Idle Air Control motor. This is very common on older cars. The IAC motor gets lazy and cant keep up with the fast idle changes. Also when the IAC motor is out, I rec to check the passages for carbon build up. If they are plugged they need to be cleaned out.

Check for the following conditions:

Poor connection at PCM or IAC motor. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
Damaged harness. Inspect the wiring harness for damage.
Restricted air intake system. Check for a possible collapsed air intake duct, restricted air filter element, or foreign objects blocking the air intake system.
Throttle body. Check for objects blocking the IAC passage or throttle bore, excessive deposits in the IAC passage and on the IAC pintle, and excessive deposits in the throttle bore and on the throttle plate. Check for a sticking throttle plate. Also inspect the IAC passage for deposits or objects which will not allow the IAC pintle to fully extend.
Vacuum leak. Check for a condition that causes a vacuum leak, such as disconnected or damaged hoses, leaks at EGR valve and EGR pipe to intake manifold, leaks at throttle body, faulty or incorrectly installed PCV valve, leaks at intake manifold brake booster hose disconnected, oil filler cap, oil level indicator loose or missing, etc..
Customer: replied 7 years ago.
do you think its a vacuum leak or my IAC?
It could be either. Unplug the IAC motor and see if the problem continues. If it does, its not the IAC motor.
Customer: replied 7 years ago.
ok i will try this cause i check all my vaccuum and everything is alright can it be my map sensor on my tps??? my check engine is not illuminated so can it be?
There is a slight chance that it can be those.

However, when I come across this problem, it usually is a air or vacuum leak, a bad IAC motor, or sometimes it is low on coolant.

You can unplug the IAC or even remove it from the throttle body and plug up the whole and see if the problem goes away.

I hope this helps. You can always accept my answer now, and repost back again later on if you have any more questions. If you want to discuss it some more just hit "reply", it's free to do so otherwise don't forget to hit "accept" and leave positive feedback if you found my answer helpful.


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