P303, P353 codes - how much to fix?

[noblerare]

Hi guys, I am new here.  I have a 2004 Lexus ES330.  I am the second owner and have owned it since 2012.  It is currently at 64000 miles and I am based on Hawaii. 

For the past few days, the engine has been running quite rough and shaking as well.  When the check engine light first came on, it was blinking for a while and then remained solid.  The codes are P0303 and P0353.  

I took it to a local mechanic and he said that there are two cylinders misfiring.  He said there were oil leakage inside the valves and quoted me $1200 to fix it as well as the ignition coil.  He said that the cylinders are underneath the engine.  

I want to ask is this reasonable or is he ripping me off?

 

[gbhrps]

noblerare,

First off, the codes say #3 cylinder (center one at the firewall) is missing, which could be the plug, the ignition wire to the coil on the plug, the ignition coil on the plug, an oxygen sensor, or a fuel injector. The 353 code suggests that you can eliminate the 02 sensor and the fuel injector to #3 cylinder as the issue.

The 353 code says there isn't sufficient circuit voltage to #3 coil (coil on plug). Basically the ignition coil is part of the spark plug boot that goes over the spark plug.

The codes don't say anything about a 2nd cylinder.

Unfortunately the 3 plugs at the firewall are located under the intake manifold, which has to come off to get at them. Its not hard to do, just time consuming = dollars. The front 3 are easy to get at.

As for oil leaking into the cylinders (if this is actually happening), it could be leaky valve stem guide seals, which means pulling the valve train from the heads to replace them. This is time consuming = dollars. The only other way for oil to get in there is a leaky head gasket, and your guy isn't suggesting enough money for that to be done.

Regardless, if you're going to pull the manifold to get at back 3 plugs, change all of the plugs to the factory iridiums at the same time for all 6 cylinders, because they are due to be changed at 100 000 miles and you're over half way there. (You'd have to pull that manifold again in 35 000 miles, so do it now and you're good for another 100 000 mi.)

If you have any thoughts as to whether you're getting scammed, get a 2nd opinion from another mechanic, before you make a decision to go ahead. Good Luck!