it's possible that you have a ground issue.....while you're waiting for the ultra gauge...check out all the ground points there's at least a couple under the hood and one behind the drivers side kick panel that seems to be problematic...possibly while you were pushing buttons on the dash..that jarred something into a better connection

 

Replaced the ECM coolant temperature sensor this evening just before the storms rolled in. It was a pretty straight forward process. The old sensor looked relatively new and I considered packing the tools up and calling it a day. But that lunacy passed. The old one came out easily. I had expected some fluid to leak out based on the RAVE manual instructions. But none flowed. When I compared the old sensor to the new one, I became concerned that I had the wrong part as the newer sensor threading seemed narrower and did not appear to extend down as far from the top of the sensor connector. The sensor shaft also seemed narrower. I inserted the new sensor and screwed it in a little just to make sure the treads would catch. It seemed to fit. So, I pulled it out, added the brass ring, some lock tight, screwed the unit in and attached the sensor plug. Climbed into truck, turned the ignition and she fired right up with less of a rumble and seemed to be running smoother. So, I guess it's a waiting game to see if this fixed the warm start issue. I tried picking up a fuel pressure sensor at ORielly's but the only one they had only went up to 15 PSI. The Ultra Gauge came in yesterday and seemed to be working fine. However, today it kept cycling between connecting and disconnecting. I was hoping it would provide the fuel pressure readings but that seems to be unsupported on the 96 Disco. Looks like engine temperature, MAF sensor, oxygen sensors, oil pressure, speed and rpm are about all useful gauges provided.

 

I took the truck for a run through the mountains, roughly 80 miles, and the open/closed loop gauge on my Ultra Gauge unit read zero, open, for the entire journey. I just replaced the ECM coolant temperature sensor and the PO replaced the fuel temperature sensor in the fall of 2015. The 02 sensors appear to be working as the Ultra Gauge shows all four 02 sensors with 1 and the occasional 0 (About 10 pm I reset the gauge to reflect decimal values and started the truck up. The sensor values ranged from 0.10 to 1.25 during the few minutes I let the truck idle. They all seemed to fluctuate about the same.). The MAF sensor went from about 0.05 g/s to up to about 0.76 g/s during the journey. So, what is the next logical step to take in resolving this issue? Any assistance will be greatly appreciated.

 

Any thoughts on how to resolve my open loop problem? New O2 sensors?

 

Open loop/closed loop is predicated by the O2 sensors. What brand and part number 02 did you install? Is your Check Engine Light on and if so what codes does the UG give?

 

Haven't installed any O2 sensors, yet. Replaced the ECM coolant temp sensor to address the warm restart problem. Got the Ultragauge and noticed the open loop which is what I thought the temp sensor problem was causing, i.e. dumping to much fuel on warm start. Read a bunch of posts and those pointed to O2 sensor. Just wanted some feedback if O2s are the most likely culprit or is something else more likely the cause. Appreciate all the help. Last time I work on vehicles the only gauges were speed, tach, temp and fuel.

Forgot to mention - no codes are showing.

 

OK at idle, upstream o2 should jump around, MAF should hold steady at .05 or so, the TPS should be around 12 +/- but steady, warmed up the coolant should be over 175*f and the voltage over 13volt

Upstream o2 replace as a pair ntk on amazon are cheap

 

At idle my
TPS is 12.2
Volt 14.26
Intake temp should read same as engine temp first start of the day
Mass air .08 +/-
Timing 28 +/-
Bank 1 o2 1 and bank 2 o2 1 both fluxuate after closed loop
Rpm is 700 +/-
Engine temp 177 +/- 180* thermostat

 

If you are having issues connecting and you do not have the voltage I said above or close, start cleaning grounds

 

Tom R - Are the 02 values fluctuating enough to indicate the sensors are working? My voltage looks to be in line, between 13.3 and 13.9. TPS is 13 and steady. The Timing is 10-11 which is significantly lower than the 28 your getting. Is that do to my truck running open loop?

At idle before leaving work
O2 B1S1 between 0.01 and 1.22
O2 B2S1 between 0.01 and 1.21
MAF 0.08 g/s
TPS 13 & steady
Timing 11
Volt 13.81 - 13.94
Intake (68) = Coolant at Start
Coolant (115)
RPM =780

At idle 10 minutes / 4 miles later at home
O2 B1S1 between 0.01 and 1.22 (same)
O2 B2S1 between 0.01 and 1.21 (same)
MAF 0.05 g/s
TPS 13 & steady (same)
Timing 10
Volt 13.36 - 13.66
Intake (68)
Coolant (178)
RPM 695

I'll track down some sensors on Amazon and swap them out. Appreciate the feedback from all.