2000 Volvo S80 2.9 Long Term Fuel Trim

[THAI UNG]

When my car was new there was a rubber cap plugged on that vacuum connector,and 4 years later that cap cracked and CEL flash on and off (I don't remember what code numbers were,but I remembered it say "vacuum leak" when I plug the OBDII tester in).After put a new nylon cap on and cleared the code,since then the code never show up again till present day,over the last 11 years. I think you need to plug that vacuume connector,clear the codes, drive it a few day than check to see if the codes are gone .I think the purpose of that vacuum connector is for the services department to hook up vacuume tester to test or check how much vacuume the engine pull and to find out any vacuum leak around the intake system like Brake booster, check valve,hoses,gaskets,etc.I could be wrong...

[jaru]

Thanks everybody,
Today I put a cap on the second port, but nothing changed. I found the vacuum diagram and checked each hose, but didn't find anything wrong. I used propane like suggested and the only time the RPM's went up is when I sprayed propane directly into the second connector on the manifold (the one I just put a cap on). What I can say with certainty is that the LT FLTRM1 and LT FTRM2 never ever changes regardless of what I do. It always remains at -.08. Does anyone know what the function of the PCV, Purge, Canister and the Shut-off-valve is?