How do you test a coil pack?
It's distributerless, single coil pack ignition system.
I don't know how to check it's working 100%, it's coming down to this or the o2 sensor for rough running / misfiring.
The o2 sensor has caused a code to be thrown (compensation out of upper range limit) but no check engine light. When i hook it up to vagcom / vcds on the laptop, the o2 sensor is still switching ~8 times in 10 seconds when the engine's all warmed up.
The car runs slightly rough when first started. A little accelerator clears it for a few seconds. When the car's warm it's running terribly, revs up and down like a yoyo at idle, almost stalling.
This all just confirms it's the o2 sensor doesn't it... still i'd prefer to know a way to test the coil pack. Plugs and HT leads are new.
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Try testing all the coil packs with an ohm meter to see if one is faulty.
Primary winding: disconnect each coil pack's connector and touch the multimeter's 2 terminals on the 2 pins of a coilpack, and make a note of the reading you get on the digital display. repeat for all 4 coils.
Secondary winding: remove the coil and measure resistance from the spring that the plug touches to one of the pins (try both, only 1 will give a reading)
A result of "0" or "err" or infinite or open circuit means the coil is faulty, if one is significantly different ot the others it means it is worn and should be replaced.
As a rough guide, the primary winding on a coil usually has a resistance of 2 ohms and the secondary winding on a coil usually has a resistance of 3-5k ohms (note the K)
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The coil pack on these is not easy to test as it incorporates an ignition amplifier and there is no direct connection to the primary and secondary windings.However from your fault description and the fact that vag com shows and out of range lambda sensor,I would be looking for a possible air leak on the inlet or breather system.Also make sure the throttle plate is clean and reset adaptions.Check the data from the coolant temp sensor to verify it is reading accurately.Lastly check the engine oil level.Overfilled sump can cause this problem.hth
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Thanks for these replies guys.
Carmalade i can hear a suction noise which wasn't there before, around the area of the throttle body but i cant find the leak yet. Will investigate further in daylight tomorrow.
Just noticed the sump gasket's leaking... great, another job to do! I love it really...
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Turned out to be a split in the breather pipe that hosts the PCV valve and joins onto the main air intake between the MAF and throttle body.
Thought about duct tape to seal the split but the PCV valve seems to be knackered too. Thought about just venting to atmosphere and taping up the breather but i've been a good guy and ordered a new part... £28!
Hope the parts man wears a balaclava.
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Volkswagen Golf IV - 98 1.6 Testing a coil pack - Dog
