# 2004 Sonata 4cyl - missing and codes listed



## dbk4297 (May 19, 2008)

Hello,

I sure thought I posted this, but don't see it listed ...

I have a 2004 Hyundai Sonata 4cyl w/auto transmission and 108K miles.
During driving the car started missing badly and losing power. The check engine light came on steady.

I borrowed a code tester and found four codes stored. P0300, P0303, P0302, and P0250.
I tested the two coils and found that the coil feeding cyls 2 and 3 had no continuity between both outputs. The spec lists 20K ohms is normal and the second coil tested OK. I replaced the coil with a new one and reset the codes.

During the test drive the car ran very well for 10 miles before the problem started again. Again the check engine light came on.
I tested for codes and found one code stored. P0350

I checked all connections and visually checked all wires finding no problems. I tested both coil connectors and both have correct voltage and ground. I went ahead and replaced the spark plugs, and spayed the area with water in a dark garage looking for any arching and found none.

Does anyone know what to check next, or what the problem might be?

Thanks in advance,
Darrell


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## qldit (Mar 26, 2007)

Good Morning dbk4297, as you are aware the coilpacks deliver substantially high voltage.

The normal path for that voltage to disipate is through a finite path of the spark plug lead and a preset gap in the sparkplug where the arc is used to fire the fuel.

If a circumstance occurs where that "finite path" is not within the designed load, it is possible for the high voltage to arc between windings inside the coilpack, which can have effect as to cause failure of driver or internal circuit components including windings.

You troubleshooting appears excellent and you have obviously determined a "hard fault". (where the problem is permanent)

In many cases it is recommended to replace sparkplug leads at intervals to ensure the path is proper and odd generated problems do not occur.

Although you mention you have replaced the coilpack you do not mention if you have replaced the sparkplug leads and in that you mention that 2 secondary circuits were affected it circumstantially may be caused by a lead problem.

Even running an engine with a lead disconnected from a sparkplug can have detrimental effect on a coilpack.

I don't have a readout on that code you mention but it obviously appears to relate to ignition.

Have you replaced the sparkplug leads?

These kind of problems can easily create a "domino" kind of problem.

Your mention of the fault clearing for a period also is strange, have you checked the battery voltage is not exceeding 14.4 volts approximately, if it were much above this kind of voltage, a higher energy effect could appear in various circuits and may not be easily recognisable and have odd effect.

Excessively gapped and incorrect type sparkplugs may also have adverse loading effect in some of these critical designed areas.

Others will have different ideas.

Cheers, qldit.


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## hashil (May 22, 2008)

hi

first i would ask you some equastions

when did you replace the timimg belt?

if you did not do. i can sure it is that. the procedure of replacing timing belt is long and i can send to you by email.


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## dbk4297 (May 19, 2008)

qldit said:


> ...Clipped
> Have you replaced the sparkplug leads?
> 
> These kind of problems can easily create a "domino" kind of problem.
> ...


Hi and thanks for your response,
I have not replaced the spark plug leads. I did test their resistance checked their contacts, and tested their insulation with a hi-pot.
The plugs are the correct type and gap.

Thanks,
Darrell


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## dbk4297 (May 19, 2008)

hashil said:


> hi
> 
> first i would ask you some equastions
> 
> ...


Hi and thanks for answering,
The timing belt was replaced by the dealer about 12K miles ago. They also replaced many other related parts at the same time.

If the belt was the cause of this problem would the car throw another code other than P0350?

Darrell


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## qldit (Mar 26, 2007)

Good Morning dbk4297, at this point in time it may be an idea to do a compression check to confirm the cylinder pressures are relatively balanced.

The reasoning here is simply to ensure you are not being distracted by a possible different problem with cylinders 2 and 3 and a possible head gasket type problem.
It is not all that uncommon for a head gasket problem between cylinders 2 and 3.

Another simple trick is to get a small portable radio and tune it to the low end of the AM band and hold it near the running engine and simply listen to the "clack clack" sound which will be received as radiated noise, the regularity of the "clacking" will give a fair idea as to whether the ignition is regular and even or erratic. This can sometimes be very helpful for analysis information.

Can't think of any other idea to assist you, sorry.

Others will have different ideas.

Cheers, qldit.


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## hashil (May 22, 2008)

i have sonata 2006 repair manual. i don't know if it will help you or not. if you like where i can upload it.


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## Wrench97 (May 10, 2008)

P0350 is a code for a defective coil did you recheck the new coil?
New parts do fail at times but I would change the plugs and plug wires
as well as the coil.


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