LS430430

Hello, I have a 2003 LS430 with the UL, Ultra premium Luxury package. It has 115000 miles on it. I bought it in December of 2016. Never had any issues with it, Just about 2 months ago, my check engine light came on. I have a fairly good code reader. I checked it and it was a P0456, a very small vacuum leak. I replaced the gas cap with a new one and cleared the code. Everything back to normal and no problems until just last week. The check engine light came on again, and this time, random misfire, on all cylinders. It was giving me all kinds of P0300s, P0301, P0302. etc. The car was still running fine for a few more days, no hesitations, or nothing that I could feel while driving it, all the while, the check engine light was on. Starting 2 days ago, the RPM goes up and down a lot when I first start it, once it warms up, that goes away, it drives fine still, but at times, it feels like it is mifiring, and I can tell that by a sudden jolt of the car while on the highway. I have only done one thing after doing a lot of research, and that is replacing the Mass Air Flow sensor, which didn't change anything. I would appreciate any thoughts or suggestions.

rkw77080

Here's what the repair manual says about your symptoms. Hope the chart below and the attachment are useful...

LS430430

Thanks rkw. I will check as many as I can.

LS430inDE.

Stating the obvious, but the fault seems common to all cylinders.

A very easy DIY is the engine coolant temp sensor. It has an affect on all cylinders indirectly. I'd even go out on a limb and say it should be replaced as preventive maintenance at 100k. It's an easy DIY since it's only a harness with 2 wires and easy to access/disconnect, easy location near the front to work on it, and the sensor is inexpensive, especially aftermarket. Beck/Arnley on RockAuto is about $10, but amazingly, Toyota/Lexus everywhere online is about $55-60! The p/n for your 2003 is 89422-30030.

Here is RockAuto's page... http://www.rockauto.com/en/catalog/l...+/+sensor,4748

I recall about a teaspoon of coolant leaking out when I removed my old temp sensor. I did mine as a preventive measure. I did Beck/Arnley.

While you're there, make sure your coolant is at the proper level by looking at the the overflow tank!

LS430430

Thanks a lot LS430inDE, I will certainly do that. It is simple enough. Where exactly is the location?

LS430inDE.

On my 2005, at the front of the engine, slightly offset to the driver's side I think? Can't recall if I took the plastic decorative cover off or not to gain access.

LS430430

Got it, thanks.

LS430inDE.

Here's a great thread showing the coolant temp sensor...

https://www.clublexus.com/forums/ls-...re-sensor.html

LS430430

Perfect, thanks.