Hey All,

I have it in mind to put new spark plugs in my RX400H, and do a compression test if I can figure out how.

This vehicle has about 248K miles, and might still have the original spark plugs.

I haven't changed them in the time we've owned the car, and there is no record of them ever being changed at the dealership.

Recently mileage has fallen off, and a rough idle has developed at start-up - probably time,

I have the Repair Manual instructions for making a compression test, but some steps are a little vague, so any tips or insights from those of you who know would be appreciated.

For instance, just how is the engine cranked during the compression test, from the key while in Maintenance Mode - or from one of the Active Test modes?

Can a compression test be done without Techstream (or an Intelligent Tester)?

Thanks in advance!

-M

 

OK, so I made a try at the spark plugs and compression test.

First, much thanks to Alchemist and 5W40 for the helpful DIY instructions and great pictures.

rx-second-generation/689263-rx330-rear-spark-plug-change-diy-with-pics
rx-2nd-gen-2004-2009/788610-2006-rx330-awd-rear-spark-plug-replacement.html#post9083036

Here's what I learned.

1) Unclipping the wiring harness from the firewall was essential for me to get at that 14 mm surge tank support bracket bolt. It gave me just a bit more room to get my hand in there.



2) The plugs were very old, and in bad shape. #6 has a cracked insulator, carbon and ash buildup on on all - except number #5 (ominous foreshadowing).




3) I eventually figured out how to crank the engine for the compression test.
a) First need to reconnect the MAF and the Coils
b) With IGN ON, and not READY
b) Using the bidirectional scan tool (I used an XTool A30M), enter the ECU Compression Test mode under HV ECU.
c) Request cranking and then Turn the key to start, and immediately press and hold accelerator pedal full down
d) Keep the accelerator pedal down and the engine will crank for 3-4 revs
e) turn off engine and repeat for each cylinder

The precise sequence may vary based on your tool.

4) Here is the most important part about the compression test - Start with a full charge on the HV Battery!!

I started with one bar over half - after monkeying around with the scan tool, and trying to figure out why the compression gage was a flat line 0 psi (gage is defunt) - I soon was down to just 2 bars!

So I stopped the compression test.

Now I'm hoping there is enough left in the HV Battery to start the engine when I get it all back together.

5) Oh yeah, and there is coolant in cylinder #5. So now I know where the missing coolant went (see earlier post on overheating).




6) Also, the PCV valve is stuck open. Surge tank is coated with oil.

Went to the dealership for a new PCV among other things.

While I was there I sat in a new RX 450h F-Sport, I do like that red interior.

Now to put it back together - maybe clean the Oil Control Valve and filter screen.

-M

 

#5 plug does look like it gets a regular washing but I don't see coolant staining. What colour is your coolant?

 

The coolant is pink - though a bit thin. After the recent overheating, I topped of the radiator with about 3 qts. of water.

I had already decided to change the plugs, and knew I would need to drain the coolant.

Anyway, the ratio is probably more like 20/80 coolant/water than 50/50.

In daylight there is a slight pink cast to the insulator of #5 plug, and on the ground electrode - but my eyes might be playing tricks.