Hard Start 2002 Lexus ES300 engine temp says it 169 degrees cold on 30 degree da

Hard Start 2002 Lexus ES300 engine temp says it 169 degrees cold on 30 degrees day.

I think this sensor is my problem but not sure which one to go after. I look up the part on NAPA it shows 2 sensors. I know one is for the Gauge and one is for the computer. But there was also something on the NAPA website about a temp sensor for the fuel system. Does this year have that in the fuel system and is that the one the computer is reading. The computer readings compared to my gun readings are way off. when running after I change the stat because it was running really hot and the hose to the bottom tank was only showing about 140 degrees. I notice the fans were not on. But they are working when the AC switch is pushed. The bottom tank was getting hot enough to trip the fan switch. After looking at it I decided to let it cool off till the next day and check the computer and see what the temp was.

When I checked it said 169 and it was 34 degrees out. So I think it causing the system not to go into cold start mode and not enriching the fuel to start. You have to fight it to start it. You have to push the pedal to the floor and hold it and keep letting up and pushing down till it starts. At first, I thought the pump was bad but once it running and warms up it runs great with no problems. Then you can start it just fine after you shut it off.

So my question is which sensor works the ECM if it has both a System temp and a fuel system temp?

Unplugging each sensor while watching the ECT PID should identify which sensor is which.

Look for another coolant temp. sensor on the engine block, -head or close to the thermostat housing. The ECM coolant temp. sensor for the engine, will not be the same as, the fuel temp sensor.

Maybe you can tell me, I am not up on Lexus systems? I not sure what this sensor does in the system it's called a Fuel Injection Temperature Sensor. Does this temp sensor control the cold start and fuel delivery? It is the one on the Scanner, that says it was 169 degrees and the engine was about 34 degrees that day and I check again after that it still said 140 on that day. When I unplugged it, it went to -30. It acts like it not getting fuel when it cold. When it's warm it runs perfect.

That sounds like a two wire Engine Coolant Temperature sensor to me. The hard start symptoms you're describing make sense given that the sensor signal is skewed high. Cold air is denser and requires a proportional amount of fuel for combustion, and it definitely sounds like your Lexus is starving for fuel when cold. :silly:

With the sensor unplugged, key on engine off, measure voltage on both wires. Should be 5.0V and 0V. Then short the two wires together and recheck for voltage. Should be 0V. You can also look at your temperature PID again - should be 250 degrees or higher. If those tests pass, you're good to install a new ECT.

I need to start making videos of this stuff for you guys. if it's weird or off the wall it seems to end up at my place because no one can figure it out or they won't time the time too. So, they try and throw parts at the problem hoping they fixed it.

I've been doing this for 35 years and learn most of it from the school of hard knocks because back then there was nowhere to learn it from. So, I had to think about how to test things. The places I've worked have been paid by Ford and GM for finding the problem they couldn't at the dealerships. The last place I work last Sygma was a test center for Cummings engine our fleet of 110 tractors. You've probably seen our trucks we deliver food to places like Wendy's. It's what I call high-pressure mechanics we have to have 100 trucks a day running to make the runs every day.

Minor wrote: I need to start making videos of this stuff for you guys. if it's weird or off the wall it seems to end up at my place because no one can figure it out or they won't time the time too. So, they try and throw parts at the problem hoping they fixed it.

You're definitely in the right forum. :lol:

Case in point, I had an '08 Wrangler come to me after other techs had tried to fix repeated overheating and thermostat codes. Coolant had leaked through the ECT into the connector, causing the ECT signal to max out at 150 degrees. :silly: Naturally, the PCM flagged a failed thermostat. It also never saw the engine overheating at idle, and thus never turned the fans on. Oops!

OK, it was the fuel temp sensor. Just so you'll know I checked the wires and did the test you suggested. The 5.0 Volts was there but when I jump the 2 wires together it didn't change anything. I think maybe there had to be resistance to get a reading. So, I got the new sensor and plugged it in. It read 67 degrees which was the room temp where it was. After installing it, it went to 37 degrees. Hint the key and it started perfectly.