I have a 99 rx300 and have replaced 2 sets of coils now at 1000 each time the first time was when I bought the car it was supposed to be the only issue but then they failed again like 5 of them mechanic says the first set was just a dud set of coils but I find it hard to believe I feel like I'm just waiting for this new set to fail I'm sick of dropping money on this same problem my mechanic seems to have no idea what's happening if it's not just a dud set of coils what could it be ? Is there a common issue that could cause ignition coils to fail repeatedly with this model?

 

I've never replaced all coils. Just whichever one failed, and they never fail all at once. Only replaced with Denso coils.

Are you using Denso coils, and how do you know they are all bad?

 

Not a common problem but few things can reduce the life.

1. Bad plugs. Use OEM only. [You can experiment but then the life of the coil-pack may be different]. The plugs are suggested to be replaced around 110K miles.
2. Oil in the plug tubes. Bad seals in the valve cover will introduce oil in the tubes.
3. Bad or inferior coil packs. Stay OEM and only buy from reputable sellers. Knockoffs and inferior products are available.

Salim

 

Cylinder misfire first one then another until I had a total of 5 misfires in different cylinders infact in every cylinder except the one my mechanic initially replaced that's why he thinks they were duds I'm not sure the exact brand of coils he said that the ones he took out he couldn't find the brand on them but he said the new ones are supposed to be pretty much original stock so idk

 

When you get multiple codes usually the right answer is clear all codes and then address the first one that happens.
With coils, swap the one from the first reported misfire cylinder with one from another cylinder. Clear the codes and see if the problem moves.

 

I have similar issues but now that you have a whole bunch of coils keep them also notice the genuine ones weigh 3 x the weight get what you pay for,

 

I did not know that ... it very well could be aluminum wires instead of copper. [unsubstantiated]

Salim