Trouble with Engine Code P0300 P0301 P0304
 

I have replaced coils, wires, spark plugs and even timing belt. I even did a compression test and the compression is right around 160 psi. My next option is to replace the Mass Air Flow. I don't know what else to do with this car???? Any help will be good!

RE: Trouble with Engine Code P0300 P0301 P0304
 

Are there any driveability issues, or is it just the codes? If you just changed that stuff out, I think it might take a while for the codes to go away.

RE: Trouble with Engine Code P0300 P0301 P0304
 

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Technical Service Bulletin
Group


36 - Engine Electrical


Number


99-36-014


Subject

Date


MISFIRE CODE DIAGNOSIS

09-1999


Model





Accent1996-2000, Elantra1996-2000, Sonata1996-2000 and Tiburon1997-2000
[/align]



Misfire code diagnosis[/align]
This Technical Service Bulletin supersedes 97-90-012. Please discard the old TSB and replace it with this new one. [/align]

A Guide To Repairing Misfire Codes [/align]
Please read through this entire bulletin before using any portion of this repair guide. All terms, components and specific procedures are described in the main body of this TSB.[/align][/align]
On the 1st repair attempt:[/align]
Record misfire codes. Choose the most appropriate category from the four (4) selections below:[/align]

One cylinder has a misfire code (see procedure A) [/ol]

Paired misfire codes as described below (see procedure B)


Cylinders 1 and 4 or
cylinders 2 and 3 (4 cylinder engines)[/align]
Cylinders 1 and 4 or
cylinders 2 and 5, or
cylinders 3 and 6 (V6 engines)[/align][/ul][/ol]

Multiple cylinders have misfire codes, and/or there is a random misfire code (see procedure C) [/ol]

Misfire code (one or more) occurs only on cold startup (see procedure D) [/ol][/align]
Procedure A[/align]
(One cylinder misfire code)[/align]

Mist spark plug wires and check for arcing. [/ol]

Remove spark plugs and check for evidence of carbon tracking. [/ol]

Perform cylinder leakage (leak-down) test.


If leakage is less than 10%, continue to step 4.[/align][/ol]


If leakage is 10% or greater, remove the head to perform valve job. (See specifics in cylinder head section). [/align][/ol][/ol]

Replace spark plugs. Lightly apply dielectric grease to the spark plug wire tip/boot base. [/ol]

If misfire is in cylinder #4 (P0304) on Elantra or Tiburon, loosen and retorque the M12 cylinder head bolts to 26 ft-lbs + 60° angle + 60° angle. [/ol]

In the misfiring cylinder, swap injector with another cylinder. [/ol][/align]
Procedure B[/align]
(Two misfire codes that are coil paired; Cylinders 1 and 4 or
cylinders 2 and 3 (4 cylinder engines); Cylinders 1 and 4 or
cylinders 2 and 5, or
cylinders 3 and 6 (V6 engines))[/align]

Mist spark plug wires and check for arcing. [/ol]

Remove plugs and check for evidence of carbon tracking. [/ol]

Perform cylinder leakage (leak-down) test. [/ol]

If leakage is less than 10%, continue to step 4. [/ol]

If leakage is 10% or greater, remove the head to perform valve job. (See specifics in cylinder head section). [/ol]

Replace the coil. [/ol][/align]
Procedure C[/align]
(Multiple cylinders misfire codes, and/or a random misfire code)[/align]

Check LT (Long Term) fuel trim. If over 10%, check fuel pressure. [/ol]

Check AFS calibration against known good value. [/ol]

Check for proper operation of EGR and purge control valve. [/ol]

Mist spark wires and check for arcing. [/ol]

Remove spark plugs and check for evidence of carbon tracking. [/ol]

Perform cylinder leakage (leak-down) test.


If leakage is less than 10%, continue to step 7.[/align][/ol]


If leakage is 10% or greater, remove the head to perform valve job. (See specifics in cylinder head section).[/align][/ol][/ol]

Check fuel sample from the inlet (bottom side) of the filter to check for the presence of water or contamination. [/ol]

Check intake air supply for evidence of oil in the air cleaner or on the AFS. [/ol]

Tweak pins on