Ignition Coil: Replace 1 Vs. Replace All?

[homemechanic]

Had a couple of codes and determined it was #4 ignition coil went bad. autozone had only 1 in stock, $60. cheaper than Kragen ($110) or the dealer. . .

anyway, replaced the bad one and problem solved. does anyone recommend replace the other coils too since 1 coil went bad? 99 ES300, 156K miles.

i was thinking no one would just replace 1 spark plugs. either all or none.

[motoroil]

I wondered the same thing on my wife's grand cherokee.

I say replace one. Thats what my mechanic told me.

Spark plugs are designed to fail/be replaced, and are fairly cheap.

Ignition coils are designed to be a lifelong component, never needing replacement. They are not wear n tear components, they only fail if something breaks in them. So, I'd leave em in since thats what they are designed for. Failing ignition coils should be an anomaly, not something that happens normally over time.

My 2 cents.

[yeskay]

i had #2 failed and within months #4 failed. now i carry a spare ignition coil. i purchased from toyota for 70.

[homemechanic]

i had #2 failed and within months #4 failed. now i carry a spare ignition coil. i purchased from toyota for 70.

i decided to just buy another 5 coils to replace the rest. no point in just waiting for the coils to fail since i am going to drive this car a few more years. . .100K more miles.

as i was taking out coil #1 and #3, oil was dripping out of the coil. the spark plug tube gaskets are leaking oil. i have to use paper towel to soak up the oil and have a valve gasket and spark plug seal job waiting for me next weekend.

i guess it's a good decision to go change the other coils and found out this problem. otherwise, coil #1 and #3 might short out eventually due to oil.

[lenore]

Make sure you have good electrical contact between the plug and coil...I add dielectric grease around the cap to keep moisture out. Corrosion is death to electronics...If it starts to build up resistance the coil has to work harder and may fail...Good luck,

[motoroil]

If you found oil on them/spark plug tube seals are bad, then they probably are time bombs for failure.

Good call!

[homemechanic]

can't take any chances since driving 30K miles a year on this car.

i guess i have half day's work next weekend to replace valve cover gaskets and tube seals.

now the costs for 6 coils and gaskets: $60 x 6 + $50 + tax = $450. i guess paying this now rather than getting stuck on the road later with a bomb going off.