Pontiac Repair: 95 Pontiac Transport with idlw problem, canister purge valve, vacuum modulator

Question
QUESTION: I have 95 Pontiac Transport with a 3.8L.. The problem is the idle goes up and down at idle and when coming to a stop, you need a ft on brakes and ft on gas to keep it running while driving. Also when driving its seems to miss or sputter sometimes too. I have codes p0341, p1640, & p1670. The 341 is a cam sensor code. I talk to a Pontiac mechanic said to check to make sure the magnet is still on the cam behind the sensor which it is. I was messing around with the vacuum lines and took off the 1 that goes from transmission to the vacuum t. It ran great no stalling, but I know I need that trans line hooked up. Can I have a vacuum problem? Could it be something with the canister purge valve? Can you help me out with what it could be and what I should do?

ANSWER: I'm the guy you asked this about before. the vacuum line is not going to cause the cam or the other codes to set. You could have a vacuum modulator on the trasnmission that is leaking and that could be causing you idle problem. It needs that to control the shift patterns. So your on to something there. did you get to the bottom of the cam code?

---------- FOLLOW-UP ----------

QUESTION: Hello again.
I didn't drive it down the road with the vacuum line disconnect as I know I need this to shift. I can pretty much disconnect any vacuum line and it will run 80% better. So I disconnected the line going down to the canister at the front right underside of the van. I took it for a test drive and It ran alot better, not stalling all the time but did couple times also no spit and sputters a curing. It seems to shifts ok for 175,000 on it. How would I test the trans modulator? I did what you said on the cam deal all was fine unless I need to do something further, not sure why that code is coming up. For the other codes I do not have the a/c compressor hooked up I have a different belt on there to by-pass the compressor as it is tied up. Not sure what else to do I'm at whits end on this. Again do not want to take it to a shop. Oh another thing that has happened is with or with out the vacuum line hooked up when turning a sharp left like turning to back into a spot it will stall on me and I will not get it to re-start, I leave it set awhile then can go start it no problem. Not sure if this has anything to do with the idle problem or if this is something new? Sorry so long but trying to give you all info that I can. I appreciated all the help and advise you've been giving me.  

Answer
you can test the modulatro with a hand vacuum pump put the hose of the vaccum on the modulator and pump up the vacuum with the pump it should hold vacuum If not the modulator is leaking. if not that is not the issue here. souldn like yo uhave a vacuum leak some where with all the lines connected and on a cold engine use a can of carb cleaner and spray around all the vacuum lines and see if the idle picks up or smoothes out you found a leak. I can tell you with a cam code the engine will run gooft the engine is not in sequential injection and it makes a difference in how it will run at idle.