Armchair mechanic challenge: Help diagnose this!

[pfb]

Vehicle:
'94 Disco V8i 5-speed
90K miles

Symptom:
Intermittant problem. Sometimes is runs great. Pulls strong, idles perfectly, smooth as silk. Then I'll park it, and the next day it will run like crap. Running roughly, like all cylinders aren't firing. Then I'll shut it off again to go run an errand, and when I come back its back to running perfectly. Also very hard to start when cold, clearly flooding.

Other info:
Nice strong spark coming from the coil.
Cap & rotor look good. No arcing or visible damage.
Spark plug wires are maybe 10K miles old, no visible problems.
Fuel filter changbed about 10K miles ago.
Fuel cleaner run through (BG 44K), no diff.
NO codes! (OBDC I)
No check engine light!

Thoughs:
Could it be a bad fuel temp or coolant temp sensor? Do these things go bad often? What are the symptoms when they go bad?

O2 Sensors? I've heard about these failing, and mine are still original, but I've heard they effect idle smoothness, not 2-3K rpm smoothness.

Could it be a bad ECU? (dealer suggested it might be... ugh!)

Could it be an intermittant bad injector?

Any other thoughts or diagnoses?

 

[joey]

I would start with injectors, they can cause similar issues.

 

[Ares]

I would start by ruling out fuel pump. Check fuel pressure at the rail. What do the plugs look like right after the problem. Fouled? Gas soaked? Clean? Is it smoking when idling bad? Ive seen a blown head gasket cause small amounts of coolant to leak into a cylinder when not running and cause poor idling until its burned off.

 

[discomike]

Well for sure, it is not the O2sensors, they just slowly wear down leaving you with less and less power, no intermitent problems.
Thats my only thoughts.
Good luck,
MikeJ.