A few weeks ago a slightly older 4.0 pathfinder came in with a CEL on for a lean condition. Watching the Alpha values (Nissan fuel trims) it was clear that there was a vacuum leak. I got my propane out and went after all if the usual suspects. I could not find it. No changes at all on my graph. For the hell of it I switched to some shop solve, and found the leak At one of the intake valve actuators. I got back out my propane and checked that part again and it still didn't show any changes on my scantool where the shop solve did.
Just trying to get an idea of why that would be? It seems like if the solve could make it through, a gas would too. The only thing I can think of is that the fluid made sort of a brief seal at the leak, and that's what I was seeing on the scantool.
I wonder if it has do with the concentration (and volatility) of combustible liquid applied directly to the leak compared to the amount of gas vapor that can be sucked in through a relatively small leak.
In theory you need to disable the idle speed control and the 02 sensor then monitor the rpm, you would then likely see an rpm increase and notice smoother idle with propane. (not possible or practical on some engines)
My thoughts are like what the moderator said it has more to do with the volatility and how easily the substance is drawn into the leak.
My thoughts are propane gets sucked in and its enough to idle smooth but thats it and you do not notice it because it balances it out the mixture plus the vehicle adjusts the rpm and overall fuel mixture.
Where as your cleaner gets sucked in fairly easy as a liquid but but does not
burn so easily or as nicely in the engine so you notice that affecting the
performance of the engine because it is in excess compared to the propane.
IMHO just my 2 cents worth and definatley something to keep in mind that
the sprays that make an engine run rough, that flood an engine tend to work better for such applications.
