ok here is the problem:
when I first turn the jeep on the temp gauge raises as normal for about 30 seconds. then it falls off like it is recieving no signal. In of it self I really wouldn't care but I am assuming that the ecm is getting the same lack of signal. My mum swore she averaged 23 to 25 mpg, we are lucky if we can baby the thing to 20 and usually get around 15 in town even with driving like there is a egg under foot.
I am wondering if the two are related, might the ecm be running the engine over rich as if it is in choke mode all the time.
I have tried using a different sensor when I was replacing the head but to no avail, mind you both were used.

So is there any way i can test it?
is there a way i can trick the ECM to see if this is the culprit?
If the sensor is not at fault does any one know where to start looking for what is?

Thanks ahead

1998 4.0

 

23-25 mpg sounds high to me....low 20s hwy - mid teens city mpg is about right. CEL or codes??????? Did u try the correct sensor ('98 model), loose/broken wire, etc.?

 

so I go out and start messing with it, it seems a little loose in the plug, but wait plug is secure the plastic body itself is cracked. I give it a wiggle to reseat it then break out the high temp super glue and fire it up, bingo I now have a gauge. now as for the fuel econ, tomorrow I have a little trip that should bring the temp up enough to let everything do what it should so that should give me some insight as to if I will get any improvement.

I should note that they were both off a 98, the one on there now is from the junkyard head, the other was from the original, I wonder if it was damaged when my mum cracked the head and over heated the hell out of it