engine stalls intermittent when A/c or defrost on... since K&N

This is in the modified tech becuase it has only done this since my K&N and 2.75 in exhaust...
the old air filter was really dirty, and the old CAT was bad...
so I put a new filtercharger in the stock airbox...
and put front to rear 2.75in exhaust + magna flow hi perf CAT and Raven 55series .. sounds sweet and has more power except when the A/c Or defrost is on, then some times it will stall when i put the clutch in at a stop light or somthing.
starts right back up and has no problems after that for a while or some times it will happen at the next light.
110,000 Mi on the 4.0 HO
I got it with 73,000mi on it and i don't know about any of the sensors or anything like that.. so i want to ask before i start changing expensive sensors...
ALSo, AC/def pump makes a loud noise when its on. could that be a bad pump berring? - this has always done this since i got it so i didn't think this would be the problem...
any help would be appreciated.

hmm, two days and not even so much as a guess... i guess that means no one had this problem... Anything simular?
Guesses?
I tuned it up, new plugs, wires, check the O'2 sensors(pulled and looked for soot), every thing seems to be fine.
any ideas would be welcome...
hasta

Can't say I've had this problem or ever heard of it, but...

I'll wildy speculate anyway. I was going to replace my exhaust soon and have been reading up on them. Everything I've seen says you shouldn't go with anthing over 2.5" for the exahust, they all say sticking with the stock 2.25" or maybe going as high as 2.5" is the way to go. I've read this in posts about "back pressure", they all seem to suggest that the engine relies on a certain amount, maybe you are clearing the exhaust so fast, that there are problems from that. I have no idea why it would only happen when the AC/Def is on but maybe the stress of the compressor engaged added with lesser amount of back pressure is causing a momentary problem that is enough to stall the engine.

Like I said, I have no idea but there's a thought. Good luck.

hmm, I gave the back pressure thought before i put it on, but i figured the 55 seris 3 chamber raven should provide the adequate back pressure at idle while still alowing it to flow well at high rpms. it is designed for a v-8 with the same kind of needs.
hmm I will have to check in to it and maybe play with some other stuff maybe stick an old muffalar on or somthing..
thanks

If you have the old filter, put it back on and see what happens. If the problems stops, it was something with the filter.
My guess is it's some kind of vacuum problem. With the A/C off, does it idle high, low or normal? I bet it is compensating for a vacuum leak, but can't do it when there is a load from the A/C compressor.

A/C quit on my fioncee this week, so i had it recharged, and it seemed to fix my problem. strangely enough, it seems the low refigerant made the pump work so hard it was killing my engine. freeky huh?
Thanks for all your input.
-Muduck

OK, there are two things that can cause what you are describing. First, when you make a radical change in the parameters under which the motor runs, it takes a while for the computer to adjust, especially if you do not reset the computer. This can be done by disconnecting the battery for about 10 minutes. It will run funny for the first half dozen starts and couple of hours of running while it learns the new parameters.

Second, there is a pressure sensing switch on the power steering that senses when the PS is turn to a stall position and the pressure spikes. The switch compensates for the extra load on the engine and the computer tells the IAC to up the idle a few hundred rpms. The same thing happens when the AC compressor actuates. These signals go to the ECU which then actuates the IAC. Cleaning the IAC pintle and the throttle body can't hurt, just be careful not to ruin the TPS.