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coil pack test - 99 Chevy Malibu

This is a discussion on coil pack test - 99 Chevy Malibu within the Automotive Support forums, part of the Tech Support Forum category. My brother in law has a 1999 chevy malibu with a 3.1 engine,it starts very weakly and runs very low

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Old 01-03-2009, 12:12 PM   #1
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My brother in law has a 1999 chevy malibu with a 3.1 engine,it starts very weakly and runs very low as if if it is only running a 1-2 cylinders. I thank that maybe the coil pack(s) maybe bad. Is there a way to test these without just replacing them? Pulled the front 3 plugs out all gas fouled. It has 3 separate packs on it. Thanks in advance for any help.
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Old 01-03-2009, 01:19 PM   #2
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First - is the "Check Engine" light on? It'd be a good idea to check codes before replacing anything.
Also, obtain a spark tester and try it in each plug wire to see the quantity and quality of spark you're getting - if any.

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Old 01-04-2009, 08:32 AM   #3
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No reportedly no check engine lights. Stated it died at a stop sign, was able to start it back up then it died sometime later with no luck to sart it again, had to be towed at that point. I haven't been able to get it to run long enough to see if the check engine light is on or not. Was looking at renting a scanner just in case though and doing a compression test as well, thanks for the reply.
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Old 01-04-2009, 09:52 PM   #4
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Hi toolboy1,

Pulled the front 3 plugs out all gas fouled. It has 3 separate packs on it.
You are not getting ignition. Get a cheap volt/ohm meter. ($10 to $15) Measure the resistance of the ignition wires from the coil packs to each plug. A good wire will measure about 600 ohms per foot or less. Two foot wire should measure 1200 ohms or less. If you've never used a volt/ohm meter, just turn it on. Switch it to OHMs and put one probe to one end of the plug wire and the other probe to the other end of the wire. The reading should be equal to or less than 600 ohms per foot. (sorry if I talk in such simple terms, but many folks are unsure about how to use a meter) Also note that the plugs should be gapped to 60 thousands of an inch. (you might also have to invest in a feeler gauge) Get one at a parts store, they are cheap also. The malibu uses thin fuel mixture and the spark has to jump further to get ignition. Good idea, but not understood by everyone.

At the ignition pack and with the ignition switch to ON, check the voltage on the Pink wire at the ignition pack. Just unplug the connector and put the red probe of the volt meter to the pink terminal and the black probe to the negative battery post with the meter switched to Volts DC. The reading should be 12 to 12.7 volts. If the voltage is lower than that, put the voltage probes across the battery and see if the battery is fully charged (12 to 12.7 volts).

The old fashon way to test for ignition, is to get a spare plug, or take one out of the engine and lay it on the engine block with a spark wire pluged to it. Get someone to turn the engine over while you look for a spark across the plug gap. A nice blue spark is what you want to see. A red non-continuous spark is like no spark at all. You are looking for a good blue spark each time that engine turns over twice. Do this for each plug wire.

One more check you can make on the coil pack is the secondary resistance of each coil. It should be 5000 to 7000 ohms. Unplug each plug wire and put one meter probe into it's hole. The other probe to one of the two terminals comming out of that coil. (meter on and switched to ohms)

The PCM (computer) tells the coil pack when to fire the plugs. Note that two plugs are connected to each coil. One cylinder is on it's power stroke and fires and the other cylinder is not. That lets the car run with three coils instead of six.

The crankshaft position sensor tells the PCM when to fire a cylinder. If it tells the wrong time, the spark is not at the right time and you get no ignition (even with spark). To test the crankshaft position sensor, use the voltmeter again. Set the meter to read AC volts. Unplug the connector to the sensor and measure the volts from the sensor while the engine is cranking over (black probe and red probe on the two sensor terminal points) the sensor should put out 200 millivolts or more while the engine is turning over.

Hope all this helps and don't be reluctant to use the meter.

It would help to get a maintenance manual on the malibu.
Lot cheaper than getting it fixed at a repair shop.

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Old 01-05-2009, 02:49 AM   #5
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A way to check the coilpacks is the remove 1 at a time, if the engine bogs down or sounds different, then the coilpack is working ok. When there is no change in engine note or it doesnt bog down, the coilpack is at fault.

Oh and be pretty careful when doing it too, they produce a hell of a lot of volts.

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Old 01-05-2009, 07:03 AM   #6
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All, thanks for all of the information it is great to be able to discuss issues with people. Did a compression test on each of the cylinders, well not good news for the brother in law. 3 out of the 6 failed the compression test with 2 reading below 60 and 1 reading 0.Again thanks for all the help.

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