I largely agree with you about WD-40 being mostly worthless. It displaces water and little else. I wouldn't even call it a preservative; since it's effects tend to be short-term.Use MAPP gas
Gas will maybe get pulled in through the leaks.
WD40 just plugs the leak long enough too lead down the wrong path.
WD40 is not a diagnostic tool.
It is a preseritive with great PR
There's no such thing as MAPP gas any more--hasn't been made since 2010 or so. What's sold in the yellow cylinders now is "MAP-Pro", a deliberately misleading name for a completely different fuel gas--essentially propane with some hot-sauce mixed in. Not that much hotter than plain propane. The FTC should make them change the name; but America doesn't have functional watchdog agencies. We have lapdog agencies that should receive hearty asp-kickings.
When I look for vacuum leaks, I use aerosol carb cleaner; and NEVER NEVER "brake" cleaner.
"It wasn't getting hot enough"...define "it". The engine? The heater duct temperature? The dash gauge?Temp runs at about 202°F on the scan. Had a 195°F in originally, it wasn't getting hot enough. switched to a 205°F
A 205 thermostat has no business in a truck that works for a living, which I'd expect of a C3500.
What does the scan tool show for coolant temp?I replaced the intake temp sensor, also checked for continuity of wire back to ECM and connections.
Find out what's wrong with the idle speed. You're using too much throttle; or the idle speed is too high. Thus the high TPS voltage at idle.I only recently adjusted the idle set screw. I have it adjusted to 700 rpm in "Drive" for Minimum Idle Air Rate.
I would agree with the TPS. The manual says 0.6v, but also states less than 1.25v during diagnostics.
It is non-adjustable on the 7.4l However, before I replaced it, I slotted the last one with a dremel and was able to get it drop 20 points. But it didn't want to rise above 1.4v anymore either.
Does the spark advance work?
Curious about the "rebuilt" canister. Once upon a time, GM had considerable issues with canister purge valves; the canister would fill-up with fuel and the engine would be rich especially at idle. But that was several years before your truck was built.