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Many Failed Coils On My 2000



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onlydrive5speedcorolla

Hello all, I am a past member who has been off line for a while. I now could use some advice, so here we go. I have a 2000 CE model that i have owner for about 4 years. I bought it with 85K now has 149K. I do not have the oil burning issue yet. I am having a problem with coils going bad. Number 1 went bad at 125K. #3 at 131K, #4 at 134K, #2 at 144k, and now #3 again at 149K. I have a scan tool and get the specific cylinder misfire code. I replace the coil and clear the code and the car runs fine. I run NGK plugs, non-iridium. I am thinking that the coils are getting too much voltage? ECU? any suggestions would be great because I am afraid to drive the car. I have been using aftermarket coils. I will buy OEM however I would hate to have the car kill big money OEM coils.

Hard to say, does sound like a possible overvoltage condition running to the input side. Could also be a sparkplug impedance mismatch on the firing end as well.

The condition you are describing is not unheard of one some of the coil igniter systems - there is a Matrix owner that has gone through 6 OEM igniters. Unfortunately, he was not able to diagnose what killed those igniters, even after extensive data logging. Aftermarket should be fine, you could grab a set of OEM igniters from a salvage yard - that would give you some spare igniters for relatively low cost.

Using non-iridium plugs should not be an issue, as long as the plugs do not foul. There is a RF suppressor coil that is attached to the side of the valve cover that helps suppress electrical noise from the ignition system. If that is working intermittently, that would cause a number of issues, including burning out the coils (ECM gets confused, igniters could fire continuously, etc.)

Faulty chassis grounds and bad voltage regulation are other possibilities. Unfortunately, with electrical issues like this - hard to really pinpoint the exact cause, as there could be multiple issues running concurrently. I suggest making sure the charging system is good to go, then tracing back the wires to the igniters. Also take a look at the igniter casing and see if there is any physical damage to it - sections that are loose, leaking oil, etc.

onlydrive5speedcorolla

Thanks for the reply. As a side note, I read your tutorial about mass airflow/PCV and throttle body cleaning. That was back in 2010 and I do that service regularly. Your advice has lasting value. With regard to the ground, all 4 coils ground to the side of the head via brown wires. I removed the bolt and cleaned the terminal and head. May not matter, but worth a try. I will check the voltage at the coil pack harness and alternator output. With regard to spare coils, I was at a U-pull salvage yard of I-81 in PA last week. I grabbed two coils. I should have grabbed all 4. The car in the yard had 4 coils marked "Toyota Denso". They were covered in dust and dirt. Appears the car made it from factory to junkyard on all 4 original coils. Wish I could brag about that. I also found the old Matrix post I believe you were referring to. At least I have some options now. Thanks again.