I think my car is running too cold. Suggestions? Might be the O2 sensor, help?

[TERRA Operative]

Ok, so the silvertop 4AGE engine in my AE101 Levin is about 450km old from rebuild, but I've noticed something that might be a problem. It seems that the engine is running cold...
I have a thick alloy radiator, new water pump and thermostat, new hoses, oil cooler with thermostat bypass and a transmission cooler (not cooled by the engine coolant).

I have noticed that the temp gauge sits a little low and I'm wondering if that might be the reason it's running rather rich. Everything else on the engine is new, and there are no ECU codes at all.


Here's a pic of the temp gauge under normal operating conditions (driven about 50km), I know it's subjective to the unmarked gauge, but I don't have an actual reading of the temperature though..




Can a fellow Levin owner compare this to their gauge?
If it is too low, would installing a higher temp thermostat fix the issue?

[dnegative]

Put a sheet of paper infront of the radiator and go for another drive?

[TERRA Operative]

Once the battery is charged, I'll try blocking the front air dam in the front bar.

Another Levin owner is getting similar temps, so it might be ok. Maybe it's time to crack open the MAF...

[Dan_k36]

Factory temp gauge shud be at half, so if u have increased the coolant capacity it will take longer to get to said temp due to the heat soak, maybe block half the radiator as dneg said and go from there,

[JustenGT8]

Pretty common to see this with a street car using an oil cooler. Folk greatly underestimate the engine cooling properties of their oil. I used to put a cover over my oil cooler for street use and take it off for track work. It still did a good job on the street with the cover.

The issue you should be worried about is that oil not up to operating temp, is oil that is not lubricating as well as it should, with greater engine wear as a result. Do you have an oil temp gauge?

[TERRA Operative]

No oil temp gauge as yet, but the oil adapter block is a Greddy thermostatic one, so it should bypass the oil cooler until it warms up.


Two other AE101 silvertop Levin owners have confirmed that their cars rarely reach half way (no oil coolers etc, one is running the same alloy radiator as me), so maybe the rich running is caused by something else. I've recalibrated my throttle position sensor and shifted the AFM by two clicks towards lean, so I'll see how it goes.

[dnegative]

Err I wouldn't be touching the AFM personally.

[TERRA Operative]

I've marked where it was, so I can always return it to stock. Toyota always run their cars rich, so two clicks isn't going to hurt for testing.

I also checked the oxygen sensor and it seems to be working fine. I'll take it for a drive tomorrow and see what the Jaycar kit tells me.

[roadsailing]

did you use the right thermostat?

are the radiator hoses etc "hot" after driving?

[TERRA Operative]

Yeah, the thermostat is correct as per the Toyota EPC.
I'll check the hoses today when I take it for a spin. If I can find a thermometer, I'll pull the thermostat out and test it in in a pot of water on the stove.

[TERRA Operative]

Top radiator hose gets nice and toasty.

However, I think I have tracked down the problem....
I stuck a new oxygen sensor in when I did the rebuild, and use a universal zirconia type. From what I've read, I need a titania type sensor for the silvertop instead, which changes resistance with oxygen content instead of outputting a voltage like the zirconia type. (The ECU pinouts seem to confirm this).

Can anyone confirm this? I'll have to look at getting a zirconia type oxygen sensor to test with.

[thechuckster]

If it's a narrowband O2 sensor, then they will all work the same way (voltage varies from 0-1V depending on O2 content in exhaust gas). Things that change resistance in the exhaust will be temp sensors.

I'd be looking elsewhere as the sensor is only going to come into play for fuel enrichment at warm idle or cruise.

[knightrous]

Sounds like 'racing' or 'hi flow' thermostat that opens at 80'c instead of 88'c. I know with the hi flow one I have on my 20V AW11, I'll be cruising down the high way in the evening and the water temp will slowly creep down to 1/4 temp.
The ECU runs off a separate sensor to the dash, and mine shows that despite sitting on 1/4 temp, the motor is at 84-88'c most of the time. The other thing, do your thermo fans run all the time? If so, I found this also makes the temps drop quickly when you pull up and idle.

As per Chuck, I doubt it's the O2 sensor, to get the motor temp to come down this much with fuel enrichment, you'd have a cloud of black smoke behind you for several km

[TERRA Operative]

It's got the stock thermostat, as stock as you can get, same part number it rolled out of the factory with (but brand new).
I don't think my rich running is from the cold engine any more, it seems that the Levins sit about where it is shown in my OP pic as normal operation.



I tested the oxygen sensor on the bench with a butane torch and it tests ok, I then tested it all hooked up with my Jaycar A/F kit hooked up to the ox terminal in the diagnostic port and with a butane torch again and it tested ok, but when I have it all hooked up properly and driving, it reads waaaay lean, like off the scale lean until I'm belting along the freeway where it comes good.

This leads me to believe it's not getting hot enough until I get the exhaust flowing so it's not reading right at lower RPM/engine load. I tested the heater wires, and they read 10 ohms (the spec for this sensor is 7 ohms) so it's either a stuffed heater in the O2 sensor, or maybe the ECU isn't switching it on.
I hooked the heater straight to 12 volts and it didn't seem to heat up, but I'm not sure how long it takes, I only had it on the 12v for half a minute or so. But even when I left it connected for a few minutes and tried it with the engine idling, no dice.


If you check out this link, you'll see the three types of oxygen sensor. First is the most common Zirconia style (which I currently have fitted), then there's the wideband style, and lastly there is the Titania style which operates differently. I'm not sure what one I need , but from what I've been reading, I *think* it might be the Titania style?
http://www.autoshop101.com/forms/h37.pdf



I might grab a new OEM one from Toyota and see what happens. It is running *really* rich, I can smell it in the cabin while I'm driving.....

[dnegative]

Hope your sitting down when they quote you

I dont think the O2 sensor is related to your issues at all though