OK here is what is going on, We had our first snow last night and of course this morning i go out to start my car and It just turns over. I try and try again and finally it sputtered and came to life, the check engine light is now on with a Code 6 (coolant temp sensor). I got it warmed up and it ran fine, then i left school 3 hours later and had the same problem again then later on yet again that night with a no cold start. But if its warmed up and i shut it off it will start and run fine


Also when i drive the engine temp gauge is way to the left of cold when i am moving but when i stop it will move up to a little below half only when im sitting still

Now 2 days ago i was running test on my o2 sensor and i found out that it was running rich at idle which stumped me a little bit, but i did notice that my gas mileage was really starting to suck. could the temp sensor not reading right cause my computer to think that it is in open loop all the time which might be the cause of crappy gas mileage and the rich reading of my o2 sensor??

please someone help me out or guide me in the right direction
thanks alot .......oh yea its a 91 integra

 

Sounds like its just your o2 sensor causing your car to run like crap and cause crappy fuel mileage. The coolant temp sensor would have nothing to do with bad gas mileage. I would replace the temp sensor, o2 sensor and go ahead and put a new thermostat in. It should run fine after that.

 

i had to replace my heater core and after i did the gauge would go to bout half way with car at idle and heat worked good til i started to move then gauge dropped and it started to get cold air. so i replaced the thermostat and added some antifreeze car was pumpin heat then and been workin fine since

 

a bad engine coolant sensor can make you run rich. that is why the oxygen sensor henses rich condition. keep in mind that when runnig properly the coolant sensor sense a cold engine upon start up and enrichens fuel ratio, that why the car idles high. now when the car or coolant warm up the coolant sensor leans out the fuel ratio, that is why idle speed stabilizes at 800 rpm. if the sensoer is bad it doesn't know when the engine is cold or hot.

 

Thank you! I was about to go off on someone for posting complete bullshit ignorant information. Why do people even post if they don't know what they're talking about?

 

You're welcome

 

Hey 99Geezer, does your car have a FITV?

 

Is this a trick question? not familiar with FITV. Please ellaborate.

 

I figured out what you were asking.

Fast
Idle
Thermal
Valve

And yes I have one on my motor.
The function of that valve is to increase rpm(not a/f ratio) so that normal operation temps can come on quickly so the computer can go into closed loop to gain control of a/f ratios.

During cold starts, the ect sensor sense a cold engine and richen mixture. during this the o2 sensor voltage is high but the computer ignores the values because it is in open loop operation.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 99Geeezer &raquo;</TD></TR><TR><TD CLASS="quote">...keep in mind that when runnig properly the coolant sensor sense a cold engine upon start up and enrichens fuel ratio, that why the car idles high.</TD></TR></TABLE>

When the car is cold, the FITV allows a controlled vacuum leak to occur, allowing more air into the cylinders, which raises the rpms of the engine. As the coolant temps rise, the valve closes off the vacuum leak which brings the idle back to 750 plus or minus 50 rpms.

Yes, the Engine Coolant Temp Sensor causes the ECU to run in open loop when it senses cold temps. This open loop mode reads off predetermined fuel/ignition maps that are rich by design to safeguard the engine (but also kills gas mileage). Open loop also kicks in when a certain percentage of throttle or engine load is detected on a warm engine. When the ECTS reads enough temp and the O2 sensor is up to temp, the engine will switch to closed loop, using the O2 sensor to fine tune the engine, giving optimum fuel mileage.

 

I was getting poor gas mileage, I mean poor gas mileage, and it ended up being my main fuel relay

 

The temp sender should be changed as well, if the connection is loose or damged ,the gauge will say its cold or jump around below op temp and cold, but engine is at normal temp. Fan should still be coming on.

 

Check the simple/cheap things first, I would replace the thermostat, it sounds like it is stuck open, make sure you bleed the coolant system properly after swapping out the thermostat, even if it is not the problem, it can't hurt to repalce the thermostat, more so the older it is.

Then I would definatly check the ECT sensor, one of the symptoms of a bad ECT sensor is poor gas milage, although cold starting is not one of them, unless the sensor is indicating a warm engine, shorted ECT sensor wiring, between sensor and ECU/ECM. 94

 

Does the O2 sensor is used along with the MAF/MAP sensor to fine tune the engine? I just want to make sure if I understand the process correctly.

Thanks in advance.

 

^this. Had the same shitty gas mileage and temp gauge was always super cold when driving and my heat wasnt hot, I replaced the thermostat and it fixed everything.