It started with a P0325 knock sensor code. We thought maybe it was just a faulty sensor, however, we noticed that we had a crack in our radiator after smelling some burnt coolant. After replacing the radiator, and the thermostat (as we found it was damaged as well while we were replacing the radiator), we still got the code.

Afterwards we thought it may be the spark plugs. After taking them out, we noticed white deposits on it. I have read this is caused from using a low grade fuel (I was using regular for quite some time, but a few months have been putting in only premium). Could the spark plugs be causing a misfire, and setting off the knock sensor?

Also, I made the mistake of attempting to clean the spark plugs, and ended up getting a P1305 code for ignition coil 2. I found out that iridium spark plugs should not be cleaned, and I therefore most likely damaged them even further.

I will obviously now need to replace the spark plugs. Does anyone think the buildup on them could have caused a misfire, and therefore set off the engine knock sensor?

 

1st - Clean and check for good coil plug connection...
2nd - Swap coil to see if fault follows

 

Since you are able to check the plugs I would obviously change them ....and switch to premium gas only. I'm sure lexus engineers put that label inside your gas door for a reason. Try and clear the code after a few hiundred miles and see if that works

 

I would also check for head gasket issues while your pulling the plugs. I have seen white deposits on plugs from coolant getting into the combustion chamber. Since you had some coolant and cooling system issues this might be prudent. Just do a compression check when you have the plugs pulled out. I've heard of a sniffer that checks for combustion gasses in the coolant but I'm not familiar with the test.

 

Although lean fuel/air ratio sets the knock sensor code P0325, I believe the code was triggered from your coolant system malfunctioning / engine running hotter than normal.

Possible causes for fault code P1305
- Ignition Coil No. 2 harness is open or shorted
- Ignition Coil No. 2 circuit poor electrical connection
- Faulty Ignition Coil No. 2
- Faulty Engine Control Module (ECM)

Yes, change plugs as you already stated in your post. If you still have the fault, I bet you have a faulty connection. Inspect, clean and insure properly connected. If you are close to St Simons Island, bring it over and I'll assist you