Quote:
Originally Posted by Chateau_Nomad
I can't think of any car I've ever had - even in the early 1970s - that needed a sparkplug change before 60,000+ miles. What prompted you to change coils/plugs?
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This is a long story but somewhat relevant to your comment.....
I have a 2002 Lexus ES300 that only has 50,000 miles on it. The car has been babied and still in almost showroom condition. It uses Iridium plugs good for 100,000 miles.
Back in March the CEL started flashing and it started running very rough. Thought it might have been bad gas at first. I have a higher end OBDII scanner and the code was for a Cylinder 3 Misfire. Unfortunately cylinder 3 is the hardest to reach. Since it is FWD and engineris sideways cylinder 3 is in the middle next to the firewall.
After doing some research it seemed like the coil pack was the culprit. Toyota uses indivisual coil packs that sit on top of the spark plugs. Everything I read said I had to remove the intake plenum to get to it, which was a fair amount of work. After watching a dozen videos I decided to try and replace the coil pack without removing the plenum.
It wasn't easy but I managed to do it. I was also going to change the plug while I was in there but I was worried about breaking it off and then having trouble getting it out because it was so tight to work in there with the plenum still installed. Plus.... I figured the plugs should be fine for another 50,000 miles at least.
I reset the code.... fired it up.... two minutes later the CEL was back.
I then thought it could be a bad fuel injector after doing more research. I watched some more videos on how to use my scanner to determine if a misfire is fuel or spark related using some of the advanced functions.
Long story short the advanced functions of my scanner led me back to a spark issue. I ordered another coil pack (in case the first one I got was bad one)... two new spark plugs.... and a special socket to get back into tight spaces.
The second time around was a little easier knowing how to work back in the tight space. I managed to get the plug out so I installed the new one, second new coil pack and got things back together.
I reset the code.... fired it up.... and no CEL! I took it for a test drive and it was back to normal.
Of course I wanted to know if it was the coil pack or plug. The plug looked fine. So I first took the coil pack and the other new spark plug, connected it to the Cylinder 2 wiring since it was easy to get to and then grounded the plug against the engine block. The new plug fired fine with the coil pack.
Then I put the original spark plug into the coil pack and grounded it to the engine block...... and nothing. No spark.... not even an intermittent spark.
The insulator wasn't cracked. The tip wasn't broken. The plug looked fairly normal for a fuel injected car with 50K on it.
In 40 years of doing a lot of my own engine work across cars, snowmobiles, lawn equipment, etc., I have never seen a spark plug just die like this one did.... especially one rated for 100,000 miles
As they say.... you learn something new every day.
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