This 99 Camry will start and idle fine when engine is dead cold or hot from driving, but won't idle when engine is just barely warm. Typical sitution would be to start the car in the morning cold, no problem and has perfect high idle. Then drive to operating temperature, and get normal idle. Then let the car sit for a few hours, and if the temperature guage is just a little above cold, get a too low idle speed and engine stalls.

I've read the forum about starting/idle problems being solved with replacing the pcv valve and spray cleaning the throttle body, but this seems different because of the connection to temperature. Could this be a thermostat or temperature sensor issue? Thanks for reading.

 

The items controlled by the temp sensor are either on or off depending on temp. Can you keep the engine running by pressing on the throttle or does it die?

The throttle body is heated by the coolant as such the IAC valve may be effected by the coolant temp. Would try cleaning the IAC valve as this is an easy first try at solving the problem.

 

I get somewhat of a similar condition but it producesan idle that is just a little low and clears quickly. I suspect the IAT sensor or ECT. Both vary the resistance depending on temperature. The link below (you'll need to scroll to find) shows the temp to resistance values. Testing is easy but requires more effort than spraying the IAC valve with cleaner. If cleaning IAC does not resolve then I would suggest testing both the IAT and ECT as per the link.

http://camrystuff.com/manuals/Gen4/SFI.pdf

 

I can keep the engine running with light pressure on the throttle, am able to drive that way, and after a few minutes of warmup everything is fine. I'll try cleaning the throttle body and then check the temp. sensors as you suggest, and I'll post the results. Thanks much for the responses.

 

Hi guys,

Cleaned the throttle body with spray cleaner, lotta brown gunk removed, lotta white smoke afterwards and an error code P0115, which I cleared with my code scanner. Seems better about idleing when lukewarm, but it's an intermittent problem at a certain temperature, so we'll see... Many thanks for your help!

FYI, I also measured the water temperature sensor ohms ( I think I have the correct sensor - the one that also feeds the dashboard gauge, yes? ). Measured slightly out of range when cold, about .25 ohms, while the book says expect about 1 ohm. While warming up the ohms drop smoothly to .1, which is correct according to the chart. I'd say the sensor is reporting a temperature slightly higher than actual temperature when cold, so maybe a new sensor is in order if the problem continues.

 

P0115 Engine coolant temp circuit malfuction

Open or short in engine coolant sensor circuit or sensor. The ECU is picking up either a too high temp or too low.

 

No. Thegauge sender has one wire, the ECT sensor has two wires.

 

Runs better now after the throttle body cleaning. Last question - is the ETC sensor near the dashboard guage sensor? Seems like there's sensors near both radiator connections to the engine. The page in the manual Pedro sent doesn't look like my car exactly. Thanks.

 

You don't mean the ECT SWITCH do you? I prefer fan switch for the name then there is no confusion. http://camrystuff.com/manuals/Gen4/Coolant.pdfSee page 31. If you provide us with a pic of what you're confused about we could help better. I suspect the gauge sender and ECT sensor are in the same relative location on the engine outlet. The gauge sender will have one wire, theECT two wires. There may also be avacuum switching valve with vac lines to it.

 

The car runs better now, so measuring the ECT sensor is probably a matter of satisfying my curiosity, but thanks for your interest.

The manual says there's an ECT SENSOR that drops in resistence as the coolant warms up. There looks to be two sensors quite near each other on the passenger side, one I've identified as the temp. gauge ( yes, a 1 wire connection ), plus another sensor on the driver's side where the other engine/radiator connection is. My question was - is the ECT sensor near the guage sensor on the passenger side, or is it on the driver's side, near the throttle body? The car belongs to my GF, so I can't take a photo today...