on my way to work yesterday my car started overheating..i was almost home...'bout 2 miles. the gauge was going up everytime i the car was idling. when i rev up it drops down. this morning i tried starting the car..it won't unless i put my foot on the gas..and as soon as i take it off it shuts off...
help!!!

 

sensor problem?

 

which sensor?

 

Did you notice the SES light on when you noticed the overheating. Did you hear the cooling fans coming on or running? If the Coolant Temp. Sensor actually fails you should get the SES light on and the system goes into Fail Safe. The Fail Safe mode might also explain the engine no idle/no run that you have. The "overheating" if it occured because the cooling fans never came on, might also indicate failure of the ECT because it controls the cooling fan operation.

 

i did have the ses light on before it happened (02 sensor) the fans do come on...and the engine will stay on as long as i step on the gas a little bit.

 

Firstly, is your car a Gen.5 or Gen5.5? So the overheating was indicated by the temp. gauge as "near the top".........when sitting stationary at idle for a period of time, or moving, or both? And the cooling fans are coming on with the AC selected OFF? And the SES light was already lit (continuously) because of an O2 sensor code at the time that you noticed the overheating? Can you rev the engine past about 2500 RPM?

 

sounds like the idle control sensor is going bad or already bad, not sure about the over heating, thermostat?

 

5th gen...the overheating started as stationary. when i'm moving it would drop to normal temp.. the fans do come ON. ses light was already lit because of the o2 sensor (cattman Y and straight pipe)...Engine rev fine.

 

Any chance you can just pull the codes, which might get us away from any more guessing?

 

I've had a IACV problem so I might be able to help. If your just coasting, or idling will the RPM's stay abnormally high? (1000-1500 or so)

 

p0420

 

Yeah, thats the sensor code

 

The O2 sensor code is N/A here. That is at present the only stored code?? It just seems like a fluke of coincidence that you had the apparent overheating and now you have the no idle issue. As far as the overheating goes, with the fans operating normally, that seems to eliminate an airflow (or lack of it) issue through the rad. being the cause. Coolant flow obviously is a function of the engine RPM (assuming the thermostat is at least partially open) so right now at idle the coolant flow may not be enough to dissipate the heat, but above idle RPMs when you get moving at speed, the increased coolant flow can dissipate the heat and the temp returns to normal. That could indicate a thermostat not opening fully or a coolant blockage in the rad. As someone mentioned above the idle speed is controlled by the ECM commanding the Idle Air Control Valve. There have been issues with both. With the hood up, when you move the Ign. sw. from OFF to ON and then from OFF to ON, can you hear a weird grinding or buzzing sound from the TB?

 

Not saying it's necessarily the case here but I had the exact same symptoms when my radiator was busted on my old car - it may not even leak the coolant if the hole is small and/or towards the top of the radiator - the coolant then just evaporates and eventually there is not enough coolant to cool the engine. When you are moving, the air flow helps the cooling, but as soon as you stop...
Did you check the coolant level?

 

Good point Whiggy.......I "assumed" he would have checked coolant level first. I screwed up on the audible IACV check.......Ign. Sw. OFF to ON and then ON to OFF with a few seconds in between. This at least will tell you if the IACV is moving.

 

i had to add a gallon to top it off...like u said i think it evaporating somehow...cuz 5 days later i have to top it off.

 

The loss of about 1/2 of the coolant explains the overheat......but what's the idle doing now? After you sort everything out, do an oil change as well.

 

you should be able to see some coolant... unless you have a busted headgasket.. then you're screwed
check the exhaust to see if it's a sweet smell. i forget what color, but i think if u have burning coolant, it'll be white

 

yea i may be your MAF or IACV.

 

is the cooling fan working?

 

Stop responding to everyones post just to get your 15 post count. If you've actually read this thread, you will see that the poster said the fans are coming on.

 

I think its the maf if its idling rough one way to find out is dissconect it when its running if it runs the same its the maf if it shuts of its not

 

will that send a code to the ecu ?