Help with temp and idle problems

[jakegator]

Hello, I have a 98 explorer with 198K miles, its a standard if that matters with the OHV engine. So I have two questions, first, The guy I bought it from stuck a piece of cardboard between the radiator and the grill so that the temp gauge will rise to about a quarter inch below the N in NORMAL. I suspect he put the wrong thermostat in but thought I would get your opinions? Is there any way to test the sending unit/temp sensor?

My second question has to do with the idle. In cold weather when I start the car it will rev to 1500 maybe less and then go down to 300 rpm (I have a computer that reads the real rpms). Sometimes it will stay there for about a minute or more then go up to 900-950 and then work fine. Other times if I rev it to 2 grand and let off the gas it will drop to 100 or less and dies. Sometimes it will start and die right away. Eventually it does work just fine. Any thoughts as to what it could be? I saw a thread about the IAC so I will clean it tomorrow. I also saw a bunch of threads dealing with o rings but they were with different engines so wanted to check first?

Thanks in advanced!

 

[1992fordgreen]

Addressing the temp issue, could just be a thermostat that is stuck open or closed. Cardboard definitely doesn't belong in an engine bay...lol

And to the idle, CEL? Clean the IACV and go from there.

 

[jakegator]

The thermostat is what I suspect as well. It throws CEL for a bad o2 sensor once in a while, but hasn't since October. Im going to clean the IAC tomorrow and see if that makes a difference. Will let you know.

thanks
jake

 

[JimMadsen]

To test the thermostat:
1- drain coolant below level of the housing.
2- remove housing and thermostat.
3- bring inside and put into a pot of water on stove.
4- turn stove on and using a cooking thermometer see what temp it opens at.
5- remove from heat and allow to cool.
6- after removing from the pot, place thermostat into nearest trash can.
7- drive to parts store in another vehicle and buy a new one.
8- install and clean the pot before your wife finds out.


Seriously though, if I had questions about the function or age of a thermostat, I replace at first opportunity. Rather take the time then have it fail big time.

 

[jakegator]

Ok well I cleaned the IAC and it didnt make much difference although its -15 here so I guess I should wait till we get more normal temps next week? I agree with replacing the thermostat, im going to replace it this weekend. Could a thermostat stuck open cause the idle issue, beings as the engine never really gets to operating temp (according to the gauge) unless im doing some serious climbing?

 

[JimMadsen]

Not sure if it would, only had stuck closed myself once. Have you thought about a throttle position sensor? When mine went I got high idle sounding like a race car but who knows...

I bet some warmer temps and nice long drive will let you know how it is doing.

 

[jakegator]

I was also thinking a vacuum leak somewhere, I've had similar issues and it was a vacuum leak. Tried to put water on the lines and see if there is any sucking but it just froze right away so ill try that in warmer weather. Any idea how to test the sensors? Just rather not spend the money on a new one if its not bad. I do a 320 mile drive about twice a month on my way home from school, it works ok but something seems off (mostly suspension but occasionally the engine will surge). I suspect this is completely unrelated, I'll start a thread on it some time.

 

[JimMadsen]

http://www.ehow.com/how_5832553_check-throttle-position-sensor.html

http://www.ehow.com/how_5560848_check-idle-air-control-valve.html