terrible mileage...

[98Roamer]

Normally I get 15 during the winter, but my last tank was only 12 = very cold, longer warm up period and a lot of remote starts. Plus over the weekend my CEL came on. I'm guessing an O2 sensor.

 

[Grenvilleter]

5VZFE uses an electronic IACV or Idle Air Control Valve to regulate the idle on cold start ups. The temp of the coolant will determine how long the high idle will run.

Thank-you... I think there is the root of the problem. The coolant sensor probably just drives the gauge and has no bearing on the air/fuel mixture. If the IACV was being affected by outside air, it could delay it from leaning back even though the coolant is at proper temp perhaps?

I stuffed an old flannel rag around the temp sensor but it made no diff that
I could tell . It's not going to catch fire as I pulled out a bunch of dry leaves lol... I'll look at the IACV to see if insulating it somehow is feasible. I'll just stuff a rag in there to block the frigid cold wind from blowing on the temp sensor.
I know the cardboard in front of the rad would help by not only causing a more rapid warm up time but also by help block the wind that blows through. I'll hold off until I check on crudely insulating the IACV even if its just poking a rag in around it to stop the wind from directly blowing on it.

Thanks again for pointing that out.

 

[Drcoffee]

The IAC is only an electric valve. Its not a sensor. The ecu will read the coolant temp via a sensor as well as other sensors like the Intake air temp sensor and MAF, etc. and modulate the IAC valve opening until the engine reaches operating temp. The longer the coolant stays cold, the longer you stay at high rpm. In these temps, you can put your hand on the radiator tank outlet and not burn yourself. That would be the lower radiator hose.

There are two coolant sensors, one for the gauge and one for the ecu. The one for the computer is on top up front by the coolant outlet. The one for the gauge is under the intake runners on the drivers side.

gauge sensor location

ECM coolant sensor location

* Dont forget that our transmissions will stay in a lower gear longer until the engine reaches operating temp as well. So you will pissing away gas in 2nd gear until the gauge is registering warmth.