2003 diahatsu terios misfiring on one cylinder, tested the coil pack with blue point tester, showed faulty coil, renewed coil with genuine part, motor still misfires ??

Question edited for clarity.
Question moved from 'Speed Computers', to Pontiac G5.

The way to find which item is faulty is easy.

Clear the code

Move the plug from cylinder 2 and put it in cylinder 4. Run the car. Is the misfire still on 2 or has it moved to 4. Yes? the plug is faulty. No? Next test.

Clear the code
Move the coil pack from cylinder 2 and put it in cylinder 4. Run the car. Is the misfire still on 2 or has it moved to 4. Yes? the coil pack is faulty. No? Next test.

Same test for the injector.

If the misfire remains on 2 you need an auto-electrician with a pro grade scan tool computer which analyses every sensor and every module.

What codes P0304 & P0308 ? This just means the PCM detected a misfire on those cylinders .an could be a few different things !
What ignition type does your vehicle have coil on plug or a coil pack with 8 plug wire towers ? If you have coil on plug ignition there are two wires going to the coils , one has battery + an the other is control from PCM . Check power first with volt meter or test light . Or use a spark tester on those two cylinders . No Spark Testing control testing

The code 300 is a Random/Multiple Cylinder Misfire....a 302 is Cylinder # 2 misfire detected. ..and the same for 304 and 306..being 304 is cylinder 4 misfire and 306 is cylinder 6 misfire...All these at the same time normally is a faulty coil pack..,and or faulty coils...spark plugs.,plug wires.....It should be running horribly or barely ....However it could be internal losing compression.....It could just need a good tune up.....Disconnect battery before changing coils,wires..,or plugs in order to clear the fault codes.....

you have a bad spark plug wire on cylinder 4 or your ignition coil
(coil pack) is bad.

here is a good guide to testing coils and wires if you need it
How to Test the Coil Pack Ford 3 0L 3 8L 4 0L 4 2L

Try swapping the coil packs around - like swap #1 with #2, and swap #6 with #5, see if the misfires MOVE with the coil packs swapped to the new cylinders or if they stay with the cylinders. If they move with the coil packs, the new coil packs are bad. If they stay with the cylinders, there's a problem with those cylinders. You DID replace that camshaft sensor, right?

Have you checked your #1 and #6 injectors?

May be coil pack or plug

Hi there:

A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.


A code P0300 may mean that one or more of the following has happened:
Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer


Possible Solutions: If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.


If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.


Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.




Now, about P0660, check diagnostic test HERE.


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I believe that both 2 and 6 cylinder show up as cyl 2 on the diagnostics tester. so you will need to check the wire and plug for both cylinders.

I would check the sparkplug first, then the timing. Do you get any spark at all at # 3 ?

have you changed the ignition wires? perhaps firing order crossed? if not coil pack or ignition wires faulty how do you know it is not "FIREING" on 1 & 4 have you tested it with a spark tester tool???