Multiple Ignition Coil Failures

hillom14 · January 4, 2012

I have a 1999 RX300 with approx. 125k miles. I've have a number of different issues with ignition coils blowing. Over the course of the last three years, I have now replaced four coils on three different cylinders. One of those replacement coils could have been defective, as it blew nearly a year after being installed. Each time a coil failed, all six platinum plugs have been replaced, yet a few days ago,my mechanic pulled one of the plugs and we noticed some corrosion on it (which appeared crusty, almost like battery acid build up). I'm wondering if there's a different underlying issue that could be causing the coils to fail? or if the plugs are part of the issue that's causing the coils to fail? Anyone else having similar issues? Any insight would be greatly appreciated.

Filehorse · January 5, 2012

I had two coils fail within about 1 year at nearly the same mileage as yours. I replaced the other 4 coils preemptively since I could see a pattern developing. I think the general consensus is that the coils on this vintage RX300 are not particularly robust and failure is not that uncommon. Since each coil is independent of the others I would not suspect any kind of external influence aside from age and heat. I hope you enjoyed the ride your mechanic took you on when he replaced all the plugs twice..!! A set of plugs should easily be good for 100,000+ miles unless there is something seriously wrong with the combustion process and anything that bad is almost certain to light up the Check Engine light. Caveat emptor.

lenore · January 5, 2012

I have a 1999 RX300 with approx. 125k miles. I've have a number of different issues with ignition coils blowing. Over the course of the last three years, I have now replaced four coils on three different cylinders. One of those replacement coils could have been defective, as it blew nearly a year after being installed. Each time a coil failed, all six platinum plugs have been replaced, yet a few days ago,my mechanic pulled one of the plugs and we noticed some corrosion on it (which appeared crusty, almost like battery acid build up). I'm wondering if there's a different underlying issue that could be causing the coils to fail? or if the plugs are part of the issue that's causing the coils to fail? Anyone else having similar issues? Any insight would be greatly appreciated.

The issue may be that you are using platinum plugs, hopefully not Bosch...they are crap....The correct plug is either Ngk or denso iridium plugs which will last an easy 125k miles....The other thing that can be happeningis that moisture is getting in the plug hole...I would use dielectric grease on the rubber boot that contacts the plug. i have pulled my plugs at 125k and have zero corrosion and the [plugs looked like new. The coils will fail if there is corrosion which can cause arcing.

Domenico Nelli · January 5, 2012

I have a 1999 RX300 with approx. 125k miles. I've have a number of different issues with ignition coils blowing. Over the course of the last three years, I have now replaced four coils on three different cylinders. One of those replacement coils could have been defective, as it blew nearly a year after being installed. Each time a coil failed, all six platinum plugs have been replaced, yet a few days ago,my mechanic pulled one of the plugs and we noticed some corrosion on it (which appeared crusty, almost like battery acid build up). I'm wondering if there's a different underlying issue that could be causing the coils to fail? or if the plugs are part of the issue that's causing the coils to fail? Anyone else having similar issues? Any insight would be greatly appreciated.

The issue may be that you are using platinum plugs, hopefully not Bosch...they are crap....The correct plug is either Ngk or denso iridium plugs which will last an easy 125k miles....The other thing that can be happeningis that moisture is getting in the plug hole...I would use dielectric grease on the rubber boot that contacts the plug. i have pulled my plugs at 125k and have zero corrosion and the [plugs looked like new. The coils will fail if there is corrosion which can cause arcing.

After 120,000 miles I replaced my plugs. They were the original NGK Iridium plugs that looked like they had NO wear!!! I couldn't believe it. I think your problem also is the fact you didn't use an OE type of plug despite the fact that the fittment is the same, e.g. plug length and thread size. I replaced my plugs with the Denso's and have had no problems. Also, I thought as a general rule of thumb to replace ALL the ignition coils at once as a PM type of thing.

CaliforniaKim · October 29, 2013

I am having the same problem, and my car has less than 50,000 miles on it! I replaced an ignition coil in the past 6 months and now another one has gone out so I am replacing all the rest to hopefully prevent future problems. It is frustrating on an expensive car with such few miles!