I have a 88 F-150 with a 351w. I'm in the process of gettings things running all nice and powerful. I've heard somewhere that if the thermostat isn't working correctly it can make the EFI think funny things and cause the mixture to be off. Is that true? And, if so any recommendations as to what temperature I should install in place of the factory one.


Thanks,

~Jeremy

 

I would stay with the recommended t-stat (prob 195) b/c the PCM uses the coolant temp sensor signal to switch to closed loop and adjust the A/F ratio based on the O2 sensors. If the engine runs too cold it will stay in open loop and run on a predetermined A/F mix which may hurt gas mileage. Also a cold running engin is more likely to sludge up.

 

Thanks for the input longbed! Gas milage is something I"m definatly not getting. I haven't checked it in a while cause it always makes me sick. But last time I knew it was below 10 MPG. My foots not that heavy!!

~Jeremy

 

>I would stay with the recommended t-stat (prob 195) b/c the
>PCM uses the coolant temp sensor signal to switch to closed
>loop and adjust the A/F ratio based on the O2 sensors. If
>the engine runs too cold it will stay in open loop and run
>on a predetermined A/F mix which may hurt gas mileage. Also
>a cold running engin is more likely to sludge up.

http://www.windworker.us/

Auto Zone sold me a Wells SU201 Temperature sensor for $16.99. I got a 1" deep well socket for $7.74 at Lowe's. I got a 3/8" to 1/2" drive adapter at Tractor & Supply Co. I unscrewed the clamps on the pair of air intake hoses, pulled the cable with the assistance of a couple of small screw drivers to pry up the plug locks, and wrenched out the old SU201. With the new one correctly in place the engine now idles without stalling. It was a profitable Saturday afternoon and I'll bet I'll no longer have to fill up the gas tank so much.

One question: The engine coolant gauge isn't working. Any ideas?

 

There is a separate sender for the gauge. It screws into the intake and has a single wire hooked to it. I'm not sure exactly where it is but it is prob close to the t-stat. Unhook the wire and ground it with the key on. If the gauge is good the needle will peg past H. Have someone sitting in the seat looking at it so you don't leave the wire grounded too long (can damage the gauge). If it moves replace the sender, if it don't, replace the gauge. If you get a new sender with the gauge, replace them both (that bit me in the *** once ). Hope this helps.

 

http://www.windworker.us/
Thanks, Longbed.