sumolexus

I had several things go wrong at once and need advice.

My Rx300 started running real bad and I thought it was bad gas. It wasn't. I also developed an exhaust leak the same day. The exhaust leak turned out to be a gasket and is fixed. I had the codes checked and had several.

1. Misfires.
2. P0125
3. P1135.

I have replaced all the plugs and 1 coil pack. After this the P0125 and P1135 remain. I have also cleaned the Mass Air Flow sensor as explained on the forum DIY

I have the android app called Torque Scan and it shows my engine temp to be 170 - 174 degrees.

The Rx300 has $160,000 miles. I just bought it a few months ago. The dealer said all major maintenance was done.

Where should I start? It seems to run fine right now. No rough idle or loss of power.

Should I buy the Denso 234-9009 Oxygen Sensor from Amazon and start there?

Thanks.

carguy07

Assuming you have cleared the code and it keeps coming back, then yes I would replace the B1S1 with the Denso 234-9009.

sumolexus

Thanks. That is what I will do.

sumolexus

What should I do about the temperature problem? What is the correct operating temperature

Baetke

Minimum temp spec is 176. I use Torque Scan and it reports 177-179 on my 1999 RX when warmed up. Could be a bad temp sensor or thermostat. Where does your temp needle sit when your car is warmed up? Mine sits right on the center tick mark +/- 1 needle width.

sumolexus

It sits at the second hash mark. This is new. It used to be in the middle. Do you think I should start with the sensor or the thermostat?

Baetke

That's the challenge. The temperature gauge gets its signal from the ECU so we can't immediately tell if the THW sensor is sending bad data to the ECU or whether the thermostat is bad and the THW sensor is sending a correct, but low value because the thermostat is stuck partially open. I've attached a paper I wrote up for troubleshooting this system. It requires that you have and know how to use a voltmeter, no-touch or thermocouple thermometer, and a scan tool. Read the attached paper and let me know if you have any questions.

salimshah

fwiw ... my RX shows temp a tad above the second mark ... it is not positioned half way between the marks.

Salim

sumolexus

Thanks. I will get on this and let you know.

sumolexus

I do have one question. Does the sensor effect the actual temperature? Also is my Torque Scan app using the sensor data or something else?

Baetke

The temperature sensor just measures the temperature of the coolant, it doesn't control it. The thermostat controls the temperature by routing coolant through the radiator. The sensor is a variable resistor that changes resistance with temperature. The ECU reads this value and converts it into a temperature that you can read with your scan tool. Look for the "engine coolant temperature" PID on your scan tool.

sumolexus

According to this if my Torque Scan tells me that my coolant temp is 170 then wouldn't my problem be the thermostat?

Again thanks for the help.

Baetke

That's what I would conclude.

sumolexus

Ok. Thanks.

sumolexus

Would it be ok to get a thermostat at Oreilly's or should I get original equipment?