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Discussion Starter #1
Hey all,


Car: 2002 Kia Optima LX, 2.4L, manual transmission. 130,000 miles

Problem: The car dies during driving, it happens when the car is not under throttle and out of gear. The engine will die, then you have to quickly restart the car and it turns on.

It has times where it feels under power and stumbles a little under throttle.

Past Fixes: It is actually my GF car. Thus far I have

Replaced the fuel filter,
changed the spark plugs,
Replaced the AC compressor and recharged it.

It throws a code that reads lean fuel mixture.

She has had it in the shop a few times for various reasons.

My Thoughts:
It seems to me that maybe the fuel pump is going bad, however my experience with them are that they go out usually all of a sudden. This has been going on for a few months.


Thanks for the Help, sorry for the long post.

Dustin.
 

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2008 SpectraSX, 2014 Optima LX,2006 Jeep Liberty, Linux Mint Mate
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You said "It throws a code that reads lean fuel mixture. "
You didn't give the code number(s) so we don't know where the fuel mixture is lean..
It could be 1,2,3,or 4 fuel injectors or an overall lean condition..
Low fuel pressure can cause this condition...a weak fuel pump, a plugged fuel filter screen, a bad fuel pressure regulator that feeds the rail, power to the fuel pump could be intermittent (see below) causing the pressure to drop.

Under the hood is one of two fuse boxes. There is a fuel pump relay that can become intermittent. There is a diagram of it's location on the inside of the fuse box lid.
You may be able to "exchange" the relay with another (like the horn relay) to test if it's bad.

A fairly common problem is with the IAC (idle air control) valve on a car with this amount of mileage.. If you pull off the large rubber hose where it is attached to the throttle body (aluminum tube) and look inside you will see a metal disk (butterfly valve) that closes off the air flow.. The inside of the throttle body and the butterfly are probably covered in carbon and oil deposits... Use a soft cotton rag, some plumbers flux brushes (Harbor Freight), and a can of carburetor/choke cleaner to clean it out.. Push the bottom of the butterfly valve in to open it. Clean the areas where it contacts the throat of the throttle body so the valve does not stick when opening and closing it. If nothing else the car should run better and idle smoother.

You could also have a fuel filter screen getting plugged. It is located inside the gas tank and surrounds the fuel pump assembly.

The mention of one code without the number doesn't give us much to go on...
Dave
 

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Discussion Starter #3
You said "It throws a code that reads lean fuel mixture. "
You didn't give the code number(s) so we don't know where the fuel mixture is lean..
It could be 1,2,3,or 4 fuel injectors or an overall lean condition..
Low fuel pressure can cause this condition...a weak fuel pump, a plugged fuel filter screen, a bad fuel pressure regulator that feeds the rail, power to the fuel pump could be intermittent (see below) causing the pressure to drop.

Under the hood is one of two fuse boxes. There is a fuel pump relay that can become intermittent. There is a diagram of it's location on the inside of the fuse box lid.
You may be able to "exchange" the relay with another (like the horn relay) to test if it's bad.

A fairly common problem is with the IAC (idle air control) valve on a car with this amount of mileage.. If you pull off the large rubber hose where it is attached to the throttle body (aluminum tube) and look inside you will see a metal disk (butterfly valve) that closes off the air flow.. The inside of the throttle body and the butterfly are probably covered in carbon and oil deposits... Use a soft cotton rag, some plumbers flux brushes (Harbor Freight), and a can of carburetor/choke cleaner to clean it out.. Push the bottom of the butterfly valve in to open it. Clean the areas where it contacts the throat of the throttle body so the valve does not stick when opening and closing it. If nothing else the car should run better and idle smoother.

You could also have a fuel filter screen getting plugged. It is located inside the gas tank and surrounds the fuel pump assembly.

The mention of one code without the number doesn't give us much to go on...
Dave
OK, I will have her get the Codes read and get back with you. She lives 2hrs away or I would do it myself tonight..:)

Thanks for your help!
 

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Discussion Starter #4
After questioning my GF further. I have found out that the odometer/Speedometer is cutting in and out. I have read or been told that the cranks shaft angle sensor maybe going out causing the engine to die at times?
 

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Discussion Starter #5
Update:

Finally got my GF to get the codes its throwing.

P0171-bank 1 system too lean

P0500 Vehicle speed sensor.
 

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2008 SpectraSX, 2014 Optima LX,2006 Jeep Liberty, Linux Mint Mate
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From what I have found the "P0171-bank 1 system too lean" is usually caused by a dirty or bad MAF (mass air flow) sensor located in the large rubber hose.
Try cleaning it. You can also unplug the MAF and see if the hesitation goes away. I may set a code being unplugged but that can be cleared..

The P0500 Vehicle speed sensor is a fairly common problem with KIAs...I'm not sure where it's located on a manual 2.4L but it is an easy fix. One bolt,one connector, done.
Dave
 

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Discussion Starter #7
I have tried and unplugged the MAF sensor before and it didnt seem to help. That is why it had turned me away from that being the problem. That and I am a GM LS guy sooo....LOL
 

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2004 Optima, 2009 G8, 1986 Capri
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See if this helps:

A code P0171 may mean that one or more of the following has happened:

•The MAF (Mass Air Flow) Sensor is dirty or faulty
Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak downstream of the MAF sensor
•Possible cracked vacuum or PCV line/connection
•Faulty or stuck open PCV valve
•Failed or faulty oxygen sensor (bank 1, sensor 1)
•Sticking/plugged or failed fuel injector
•Low fuel pressure (possible plugged/dirty fuel filter!)
•Exhaust leak between engine and first oxygen sensor
Possible SolutionsA lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include:

•Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
•Inspect all vacuum and PCV hoses, replace/repair as required
•Inspect all hoses and connections in the air intake system
•Inspect and/or test the intake manifold gaskets for leakage
•Check for a dirty fuel filter and proper fuel pressure
•Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool
•If you have access, you may want to run a smoke test

As for the P0500 (speed sensor)

should be right on top of the transmission housing.
 
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