Hello,

New member here with an unexpected issue. About a year ago my wife bought an immaculate 2006 ES330. It had 47K miles and all maintenance was performed on schedule at the dealership. Everything needed since then has also been done on schedule, just not at the dealership. It's okay for a previous owner to spend that kind of money but I'm certainly not going to. All had been perfect until now. At the same time, it started running quite rough and the check engine light came on. I scanned it and got a P0304 code - Cylinder 4 Misfire.
I popped the plastic engine cover off to have a look at the coil pack and spark plug on #4 and found that there must have been a ton of heat under there at some point because all three of the front ignition coil connector clips had partially melted as well as other signs of heat. The covers to plastic cases that hold the ignition wires had also broken. The clip parts of the connectors are now non-existent. Photos are attached.
I was extremely surprised to see something like this on a vehicle that has been cared for so well. I was able to remove each connector and there was some rubbery substance on each one. Either there was some rubber in the connector that melted or somebody might have put some black permatex on there after the meltdown to keep the connectors in place now that the clip was no longer working. Either way, this must be repaired.
I checked each of the front three ignition coils and got the same readings so they seem alright. I pulled #4 spark plug and it looked fine for its age and history. I cleared the code but it was still running rough and the same code reappeared almost instantly. I suspect a bad connection at the #4 coil is causing this but am not convinced.
Questions:
1. Has anyone else experienced anything similar?
2. I plan to replace all of the front connectors. How far upstream do you have to go to do this? I found some replacement connectors that can be spliced in but would prefer to do the whole thing if it's not terribly complicated.
3. Any theories to what might have caused this?

 

Hello,

It certainly looks bad, but it doesn't seem like a melted connector, since all the other components, like the plastic cover, wiring and a rubber seal on the coil seem intact. Can you submit a photo of how the inside of the connector housing looks like?

Those plastic housings are notorious for becoming brittle after a long exposure to the heat of the engine bay, I would suspect that someone broke all the clips and then used some kind of substance to hold those in place.. Try bending the wiring to make sure that the isolation won't crumble apart in your hands, like it often happens with an overheated wiring. If that is good, then I would suggest to follow this guide on how to replace just the housings. That post also has a chart with Part Numbers for all the connector housings in the car; for my 2000 Lexus ES300, it is 90980–11885.

Hope this helps and best of luck!

 

Hi,

Thanks for the response. I put everything back together for now so can't take any more photos or examine the wires. Maybe my wording wasn't the best but what I meant to say is the outer black plastic housing of the connector was melted, not the actual connections. I was surprised that this is quite common but that is the case. I looked at your linked post and that does explain the process quite well. I also found this video which also shows the process quite clearly.
I found six housings for a good price and will replace the front three and sort out the misfire issue. The very difficult rear three will have to wait for later.

Thanks again for your input.

 

Update, I finally got around to changing out the 3 connectors and put a new ignition coil in #4. Fired it up and running smoothly. I'll check the old coil again and I do suspect it was the issue, still the connectors needed replacing and that is done now.

 

Thanks for the follow up. FYI that kind of damage is due to a bad connection this causes arcing hence high temps in a small space. This is how electrical fires generally start.

 

Also wanted to add that the melting of the connectors is not normal. What Arsenii was talking about is them becoming very brittle and crumbling when working on spark plugs. It’s a good thing you got to them before something worse may have happened.

 

Thanks, I should also have followed up with my observation that they were't melted after all. It was some type of black adhesive like Permatex that someone had put on there after the clips had snapped off. The clips themselves were extremely brittle and could be picked apart by hand, but definitely not melted.