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2007 Black RTL
9 Posts
Discussion Starter #1
This last week at 121,000 miles, I decided to finally replace my spark plugs for the first time. When I did, I found my ignition coil #4 on cylinder #5 (front-center) dirty and fouled up with brown reddish exhaust residue. Ignition coil #2 on cylinder #4 (front-left) also had a little bit of orange exhaust reside on it's tip. All the other ignition coils were clean. The plug tips were old and dirty but nothing unusual. It seems this is strictly an issue of the plugs backing out and allowing exhaust to get to the ignition coils.

Searching the forums here tells me I'm not the only one with this problem.

I have attached a few pictures.

Here's the full long-winded story for additional details:

About five months ago, back on 2019-09-23 (118,000 miles), I had a Check Engine Light + VTM-4 light event with no obvious symptoms. A few days later I put an ODBI adapter on it and got a fault code P0175: Powertrain, "System too rich (bank 2)". I didn't see this CEL event again for about two months, and had not seen it since, so whatever was causing it was very intermittent or just barely able to trigger it. The repair manual tells me bank 2 is the front-side sensor.

Knowing what I know now, I suspect this CEL event may have been related. But at the time I didn't have any other symptoms or problems so I just made a mental note that I should change my spark plugs, which I eventually did this week.

Despite it's dirty appearance, the ignition coil looked structurally sound, though I think I should go take a second look here in a few days and I'll replace it if I find any brittleness. I will also add a calendar reminder that I should go check the plugs twice a year.

The spark plugs themselves looked used but the iridium tips were all in great shape. When I removed them, I did notice that the spark plugs gave a varying degree of resistance, with plug #4 on cylinder #5 (front-center) being finger-tight only. I don't know if it had loosened up on it's own, if it was never properly installed, or how long it's been this way.

On re-installation I cranked them down fairly tight. I'm surprised to read that 13 pounds torque is all you are supposed to use. No doubt I used more than that. Hopefully I didn't deform the threads, and yes I used aluminum anti-size.

Getting the ignition coils and spark plugs out isn't too difficult, especially on the front row. Having a cheap flex ratchet and an extension of the right length is important (a TEKTON 13101 3/8-Inch set is perfect). Having a 45-degree bit driver (Dewalt DWARAFS for example) can make getting the hex bolts in and out much easier. Also, feel free to take some pliers to the radiator fan cover and bend that edge upwards for the 1/2" of clearance you need to get #2/cy4 out, then just bend it back or leave it up when done. #5/cy3 has a coolant pipe in the way but it should be soft and easy to work around. For the rear row, being tall helps, otherwise get something to stand on so you can reach back there.

Here is a list of links to the other threads I found when researching this issue:



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