Background: 2000 Disco II 139,000
Valve job @ 97,000
HG & head bolts
Valley gasket
Cleaned Injectors
New O2 sensors (4)
New coil
New wires 7 mm
New plugs
New MAF and air filter @ 102k: p0734, p0171, p0173
New CPS @ 116k
New Cats @ 130k for cracked housing : p1170

DII used as DD by my son. Recent CEL = p0134, p0305. The truck runs with a noticeable
Misfire. Cleared the codes, returned after about 300 miles. Degreased the engine in preparation for work...bad idea. After degreasing, codes expanded to include p0300, p0301,
p0303, p0307, p01300. Obviously cleaning related. After 2 days of driving approximately
100 miles and clearing the codes, p0134, p0305 reappeared. This p0134 and p0305 would
appear and disappear. Short city driving would tend to bring the CEL. Decided to put new
air filter and low and behold the codes goes out and stays out. I have to say with the new
AF the truck runs smother & with noticably more power. Codes p0134 and p0305 has not
shown up as it usually does several times in one weeks time.

Problem band aided for now.

New toy comes in Ultra Gauge EM. Came in yesterday, of course I had to try it out
@ 8 PM, boys will be boys.

Info gathered from new toy.

Truck runs at 194 deg F. Probably needs to be calibrated with my IR hand sensor.
But what's this!!! Trouble code p0134, p0305, p0301, p0303, p0307, p300, p1300
WITHOUT the truck CEL on. This only shows up after starting. The truck runs very
smooth at operating temp. Ultra Gauge even shows a 15 MPG average in the 6 mile
Run that I took it in. Still no CEL on with the Disco II.

Dx: from all this, I'll probably need a new O2 sensor, need to check wire to plug # 5
for arcing. Something tells me my heater circuit to my O2 sensor is not working.
The lack of CEL, and the it's smoothness at running temp suggest this.
The trouble code from UG is no doubt an in cycle code. Since it runs smoothly
after the initial "rough" run, the code cancels out and never makes the mandatory
2 in a row show that will trigger a hard code.

Lesson learned: Don't introduce new problems that can confound the original
Problem making diagnoses harder e.g. Cleaning the engine bay.
Should have check plug wire #5 early on.

Oxygen Sensor Trial and Error is helpful shedding some insight into this.

Will post follow up.

Ed

 

Love that Ultra Gauge.

 

Whos wires did you install, sounds like cheap ones that might be leaking especially after you tried to clean the engine.

 

IIRC it is Magnecor.
Getting back on to diagnostics, I configured the UG to display the voltages of the O2
sensors side by side for comparison. I'm getting voltage, re o2 sensor in question.
Hope I don't have a manifold leak vs crack causing a faulty lean O2 reading.
Need to look at the voltages a bit more.

Thanks For the come back.
Ed

 

UG is AWESOME!!!
Your front O2's should change volts rapidly, up and down and should be just about opposite of one another, i.e., left bank is .940v and right bank is .250v.
Then they switch, left bank is low volts and right bank is high volts.
Rear O2's should be pretty steady on the volts and not change as rapidly as they have zero to do with engine fueling.