P0307 Code

[ScottB1]

I brought my 2001 LS430 with 200k miles on it into the shop I have been going to for years (not an authorized Lexus mechanic) with a check engine light and VSC system light on.  They error code was P0307, which indicated the 7th cylinder is misfiring.  The shop recommended replacing all 8 ignition coils and spark plugs ($1,650).  The cost of the coils is the largest component of the cost (labor was only $250).  I asked them why replace all 8 coils if the code says only 1 is misfiring.  The response I was given is that they have seen this many times before and if 1 coil goes bad, they will all go bad quickly thereafter, and they wanted to save me on repeat labor costs.  My online research leads me to believe that may not be the case, that changing the coil might not even be the cause of the error, and the shop is just trying to make some extra money.  Hoping someone might have some thoughts on whether I am being taken for a ride?  Thanks.

[Lexus Owners Club]

That's a tough one....worthy of taking to another mechanic who can check all other eventualities without committing to replace expensive parts:

A quick Google search does suggest other issue including engine faults (is the oil level low, is the engine clogged up with carbon) all of which are valid and worth checking first

 

[ScottB1]

Thank you.  That's what my google search revealed too.  I will definitely take it to another mechanic.

[RX400h]

With 200k miles on the original coils, I would imagine that some maintenance is due but you did not mention how many miles are on your existing sparkplugs. I had to have ours replaced at 120,000 miles. Were yours replaced at 100,000 miles or so? If they were, then they are due for replacement.

Rockauto,com sells OEM coils for $48 each. That's $288 for 6. OEM sparkplugs are a whopping $2.33 each or about $14 for a set of 6.

So $302 for all the parts and $250 for labor - any halfway decent auto repair garage can do this, and they may let you supply the parts.

Regarding engine oil sludge. You probably know more than anyone one if your driving habits and oil change frequency would make this assumption realistic. If this were my car, I know that it is not possible, since I use synthetic oil and do not drive for very short distances.

 

[ScottB1]

Thank you for your thoughts.  My father owned this up until 16k miles ago and took meticulous care of it.  From the service records it looks like he had the valve cover gaskets replaced 25k miles ago and they replaced all 8 spark plugs at that time.

[RX400h]

You're welcome, Scott. Okay, so the spark plugs are probably just fine if they are OEM plugs. My guess is that the coil is bad. If it is easily accessible, replacing one should be a 10 minute job.

I don't think changing all coils will save you any money vs changing one. It's mostly a peace of mind type of thing.

[ScottB1]

Thank you Dave.  I think that's the route I'll take...actually I'll have my son take once our Covid numbers go down and they re-open his auto shop class in school.