Jeep Cherokee XJ 97 Crank no start sometimes it sputters

[Lenny6]

Ya would believe what I done on the weekend. Replaced some of the parts that I replaced with new ones and the car still works so I'll be putting all the parts I have in a ziplock bag and storing them under the rear seat too...

I was just curious as to whether the were dicky..

Len

[Mudgee hunter]

The coolant sensor also plays a BIG role with pcm on fuel injection etc.
Upon It failing, it can tell the pcm the motor is cold as!... permanently...
Making fuel mixture way out of whack!
Excessive fuel consumption too!

[alexbrown64]

Your right Mudgee. I have two coolant sensors. The one on the back of the head is purely for the temp gauge on the dash cluster.

The one on the thermostat housing sends signals to the computer. If it sending the wrong info, your computer may think your still warming up and keep you in open loop, or in warm up mode.

I have been using my OBD1 scanner alot, and i notice that my Jeep comes out of open loop and into close loop when the engine is only just warm. about 30-40C. But using my OBD1 touch screen fuel economy gauge, i only get full economy when the Jeep gets to about 86-88C. This is because i have my gauge set to show me my hot idle fuel burn. At warm up, even in closed loop, i am still burning fuel at 2.5-3.5lt/hour. When the engine is fully hot (86-88C), my hot idle drops to 1.7-1.8lt/hr.

I did have a faulty coolant sensor, but it was reading the opposite way, so it was probably helping me out by sending info to the computer saying that my engine was hotter than it was.

I can compare temp settings because i have an Engine Watchdog with sensors connected directly to the engine and transmission. I can then compare readings with my scanner and gauge cluster.

Cheers,