TEST 5: You Got Spark From All Boots
If all of the spark plug boots fired off spark in TEST 1 and yet the vehicle is experiencing a misfire condition, then the most likely causes are: 1) the spark plug boots spark plugs have developed carbon tracks or 2) the plastic ignition coil cover has developed cracks or carbon tracks or 3) the spark plugs and spark plug boots are swimming in engine oil or 4) all three of the aforementioned conditions. All of these conditions are a very common occurrence in the Quad 4 ignition system.
If the spark plug boots spark plugs are swimming in engine oil, it's usually due to the 'valve cover' gasket that GM uses on the cylinder head leaking engine oil or the engine oil pressure switch leaking oil. This oil will cause the ignition system to misfire and/or cause carbon tracks to form as the spark cooks the oil.
In the image below (in section: What If No Carbon Tracks Or Cracks Exist?) you'll see what a carbon track looks like on the spark plug boot, on the spark plugs. In the image above you can see an example of carbon tracks on the ignition coil housing cover. In the photo of the ignition coil cover (above) you'll notice the arrows are numbered, number 1 points to the carbon track and number 2 to the crack in the ignition coil cover. The next step is to remove the spark plugs and spark plug boots and coil cover to visually inspect them for carbon tracks and/or to see if the are all oil-soaked.
If the spark plugs are oil-soaked and/or with carbon tracks, you'll need to replace them all along with the spark plug boots. Failure to replace one without the other will only make the carbon track return and/or continue to misfire still.
What If No Carbon Tracks Or Cracks Exist?
Now, if no carbon tracks are visible on any of the spark plugs, or spark plug boots, or on the ignition coil cover AND the ignition coil cover is not cracked, then the ignition system is not the cause of your misfire condition. I would check engine compression and the fuel injectors among several things. I have written another article that will help you with these tests at: Diagnosing A Bad Ignition Coil Quad 4 Case Study.
Reader's Real Life Case Studies And Solutions
In this section, is input and feedback from all of the folks who have had a similar issue with their vehicle and found a solution. If you're one of them, thank you for sharing your experience with all of us! If you want to share your repair and/or diagnostic experience, you can use the contact form below.
Real Life Case Study 1
Vehicle: 1998 Chevy Malibu, 2.4 quad 4
Trouble Codes: None
Complaint: Cylinder #3 dead.
Repair: 'Thanks for your articles on this motor. I have worked on cars for 25 plus year (weekend mechanic, not professionally) and this had me baffled. My problem turned out being the coil cover. No cracks or carbon trace was visible, but after testing injector harness, swapping injectors, changing plug boots, swapping coils, swapping plugs, a compression test and cylinder 3 was still dead, the cover was all that was left. Really surprised me. I have seen carbon trace on plenty of other vehicles I have worked on and this showed no signs of it. Wanted to pass that along, no carbon trace doesn't mean it's not defective. ”
Courtesy of: Gary Lem
If this info saved the day, buy me a beer!
