Skypilot68

My RX 300 is stalling. It does this at various times, at all different speeds, temperatures, from after running for a couple hours, to immediately after start-up.
What happens is there is the sound of buzzing relays from behind the dash, this comes at the same time the engine begins to stall. When the buzzing stops, the engine begins to run normally. If the Check Engine Light is on, it will pulse with the vibration of the relays. No other electrical devices seem affected. The radio, lights, etc stay on and don't hesitate at all. If it happens when I am first starting the Lexus, the engine will die completely.
The codes being thrown are: shift solenoid A,B, and D, (753, 758, 768) all the igniter circuits, (1300 - 1330), P1760 - Linear solenoid for line pressure control circuit
PO171 - Bank 1 system too lean
PO420 - catalyst system efficiency below threshold Bank 1*
They don't come on at all until this happens and then they all show up. I am assuming that all of these systems are either controlled by the same component or they are all on the same circuit at some point. I have the schematic, but it is not readily obvious to me What they had in common, as I only have the hard wiring schematic, not the ECU programming or anything deeper than the wiring harness.
I have tracked down the relays that are buzzing and it a group of three one of which is the one that controls fuel pump. The Lexus dealer said that all three relays must have gone bad. I didn't buy that, and they didn't have any to change out, but just to be sure, I replaced two of the three relays, with no change.
Hoping that someone else has dealt with this previously. I am a Master Electrician and I work daily with controls, but this one has me chasing my tail.

salimshah

Was any work done on RX which could have initiated this odd behavior?

Salim

Skypilot68

Not that I'm aware of. I bought it for a great price ($2500) because it was having an issue with the VVT valves. I replaced those, and also the valve cover gaskets, plugs, and filters etc. after that, it ran without issue for about 7,000 miles. I have had an issue with the A/C, it keeps quitting, and the green light flashes, so I have to double-tap the button for a restart and then it's good for a few minutes (sometimes seconds) before it trips out again. I tightened the belt, and added the right amount of Freon, to no avail. I will replace the belt and see if that cures it, but it's Michigan and I hasn't been very warm, so with the sunroof, it really hasn't been an issue.

salimshah

There are a bunch of ground wires between the the firewall and the air intake. Feel in there and see if anything was left unhooked or even if the tiedown is loose.

Salim

Baetke

Was this car, by any chance, ever in a flood? Multiple bizarre electrical failures are often a symptom of a car that spent some time under water.

Skypilot68

I'll check the ground wires, that does make sense! as far as the flooding, it has not been underwater as far as i know and there are no other tell-tale signs of flooding, but its always a possibility.

salimshah

Carfax can tell you if an insurance claim was made due to water-damage. If things are done above board, the title would show it too.

Salim

kevinslexu

I am experiencing the same issue on my 2000 RX with 240 K miles. The buzzing sound comes from the air control unit under the dash toward the passenger side. I found out it comes from the Air conditioning or blower control unit. In a short while I noticed the blower blows only from the front vents even though On the display shows differently. It becomes random and when it buzzes the engine stalls and the gas millage becomes very low. I have seen many recommended the IACV can be an issue to stalling problem. How could the buzzing of air control unit relates to engine stalling? I have to address that the battery was dead at a time and I had to jump started it for a few times until I changed the battery, and there was no issue before that.

Any suggestions please?

salimshah

Welcome to Club Lexus.

We have some sticky threads (top portion of the thread list).
Please go through them. RX300 Mega thread, start here if you have problems ... air servos is most likely the problem.

Modern (if you allow me to use modern for 10+ years), are controlled by sensors and are susceptible to operate under wrong conditions if the battery is poor. I would suggest that you have the electrical system checked (battery & charging) and maybe replace the battery.

Post back if the problems do not go away and remember to post any CEL.

Salim