LMSeal

Need help here, all else has failed including $150 trip to the stealer.

2009 Lexus RX350 3.5L throwing codes P0300 (multiple random misfires), P0302 (misfire on cylinder 2), P0304 (misfire on cylinder 4).

Changed all spark plugs; replaced injectors on 2 and 4; replaced coils on 2, 4 and 6; changed camshaft position sensor in middle of bank 2.

When the vehicle is warmed up for 20 minutes it won’t throw the light but tester is still showing codes.

Oil consumption has increased slightly and there is excessive crankcase smoke when the oil cap is removed.

Stealership tested engine and vacuum test indicated internal engine failure. They are telling me either broke ring or bent valve. This engine has NEVER been overheated. I find it highly unlikely that two piston rings would break in cylinders side by side, or the same for valve stems bending.

Considered blown head gasket, but there is no water or coolant in the oil.

When the CE light is on steady it runs fine, when it blinks it runs bad. VSC light also blinks.

Sorry for the lengthy post, I’ve tried everything I could think of. Now I need somebody in the know to think for me. Advance thanks for your help!

Larry

bgalarpe

Do a leak down and compression test to find out where it is leaking from....you can have a blown head gasket with no water or coolant in the oil if the leak is between cylinders.

smassey321

Is there any oil in the coolant? Is there any pink crust running down the side of the engine?

Audiqv8

Agreed, do a leak down and compression test. Also, verify that your PCV valve is good working order. The PCV valve is a control device which sends partially burned gases that come from the engine's crankcase to the combustion chamber.

LMSeal

Leak down and compression check is next on the agenda. No, there is no coolant loss or evidence of any coolant leakage. I did change the PCV valve when I changed the rear spark plugs, so it is brand new. Thank you for your feedback! It confirms that my thoughts are on track.

jmu2004

I had misfire issues in the rear bank related to a bad ECU. The ECU was telling the injectors to stay open, rather than pulse. and the cylinders were flooding.

If your engine runs smoothly AT ALL, I doubt you have hardware issues.

LMSeal

Thanks for this info. Just curious, were you getting a specific CE code for the bad ECU? Were you getting the P0300 codes as well?

jmu2004

Yes. Codes were for a misfire in the rear. First check was plug, then coil. Both were fine.

I think think there may gave been an issue for awhile, as my MPG has increased about 5-7% since the ECU was replaced.

LMSeal

THANK YOU! This could very well be my problem. I've already changed plugs, injectors, coils and camshaft position sensor to no avail. I found a used (with warranty) brain box/ECU on eBay for $50. I think I am going to try this. Notes are telling me that dealer needs to install with certain codes and so forth.

I've tried everything else, may as well give this a spin. Thanks for your help!

jmu2004

It's worth a shot, for sure. Like I said earlier, I have a hard time believing internal failure if your problem is intermittent.