2001 Kia Optima Engine Stuttering when engine is cold and a

MYSTYFYDZZ

MEMBER
2001 KIA OPTIMA
4 CYL
FWD
AUTOMATIC
58,450 MILES

I had maintenance done on my car at 50,000 miles and ever since, whenever it is humid outside and my car has been sitting all day or all night, it stutters and almost stops running when I start it. It does smooth out after it warms up - usually about 10 to 15 minutes if I just sit & let it run. If I try to drive while it is still stuttering, I have one heck of a time getting it to move. Generally, if I can keep the RPM's at 2k, it runs smoothly.

I have taken it to the dealer (who did the maintenance) 3 different times, but they have not been able to find the problem.

Can you give any suggestiosn as to what could be causing this? My friend thinks it may be the spark plug wires and I'm inclined to agree but without knowing a lot about cars, I just don't know.

Thanks for any info you can provide.

3 Replies

DAVE H

MECHANIC
13,383 POSTS

There could numerous reasons for the fault you are describing. Spark plug wires is one of them. Does the CEL (check engine light) on the dash ever come on?

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Thursday, February 19th, 2009 AT 6:55 PM

MYSTYFYDZZ

MEMBER
2 POSTS

Dave H - thanks for the reply. Yes, the Check Engine Light has been staying on for about a month, then goes off until the problem happens again. I've taken it to the dealer when the light is on - they check & tell me that the code indicates a 'random mis-fire" and that it could be anything from bad gas to bad timing that would cause it.
To me, a "mis-fire" indicates the plugs &/or wires have a problem.

Thanks again for any input you can provide.

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Friday, February 20th, 2009 AT 6:01 AM

DAVE H

MECHANIC
13,383 POSTS

Because the diagnosis is random misfire I would be checking the wiring to and removing and cleaning the CKP (crankshaft position sensor)

DISTRIBUTORLESS IGNITION SYSTEM (DIS)

DIS system consists of a Crankshaft Position (CKP) sensor, Camshaft Position (CMP) sensor and 2 coils. CKP sensor is located on transaxle/transmission case near flywheel. CMP sensor is located in rear of head. On 4 cylinder engines coils are located directly on top of No. 2 and No. 4 spark plugs. On V6 coil pack is mounted on rear of cylinder head. Each coil is connected to companion cylinder spark plug by plug wire. System uses waste spark method. Each coil fires 2 spark plugs simultaneously. Sensors signal ECM which cylinder is ready to fire. The ECM then triggers appropriate coil.

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Friday, February 20th, 2009 AT 7:09 AM