a/c causes engine to stumble
05-11-2011, 08:37 AM
#21
If the compressor seems to be locking each time, it might be slugging liquid refrigerant. There is the possibility of an overcharged A/C system, air in the system, a plugged orifice tube, or all three. The only way to check is to evacuate the system and weigh in the correct amount of R134a.
05-11-2011, 07:52 PM
#22
The tuning could very well be an issue, but I don't know enough about it to tell you where to start. I can't imagine installing the blower would require any changes to the AC tables, but again, I have no idea. Personally, I would look at the AC first. what you are describing sounds alot like a compressor thats going bad (clutch partially locking up) and/or there is too much/not enough freon in the system. With the car OFF, you should have about 65 psi on BOTH the high and low side. With it operational, you should have about 30 on the low side, and 90-110 on the high. If there is too much in the system, the compressor will be drawing extra power, trying to compress it for cold air, and it will feel like what you are describing.
If there was too little R-134a in the system, the compressor would either cycle on and off constantly, or not at all. If overfilled, the compressor may get slugged like Mike suggested. If way over-filled, the high pressure switch will not allow compressor operation at all, or may quickly shut it off.
In our shop which is generally around 70*F, I usually see 30-35psi on the low side and 200-225psi on the high side with the engine running at 1500 RPM.
05-15-2011, 04:48 AM
#23
Well it appears that there are multiple possibilities, but the first thing that I would look at is the tune. LS1TRUCKGUY, it may be possible that your throttle body and IAC are dirty, and the throttle body isn't getting the true amount of air as it should. If you haven't cleaned your tb in a while, I'd give it a shot. If it doesn't help, all you lost was a little throttle body cleaner, and you got a little preventive maintenance done 
05-15-2011, 11:38 AM
#24
When you weigh-in the correct amount of freeze gas, according to the label on the truck, the pressures will tell you if the orifice is clogged. If it's clogged the pressure on the suction side will be way too low, maybe even in a vacuum. That is when Mr. Goodwrench replaces the orifice tube and starts over, and Mr. Shadetree keeps dumping in more refrigerant until the suction pressure looks reasonable.
05-16-2011, 01:17 PM
#25
When you weigh-in the correct amount of freeze gas, according to the label on the truck, the pressures will tell you if the orifice is clogged. If it's clogged the pressure on the suction side will be way too low, maybe even in a vacuum. That is when Mr. Goodwrench replaces the orifice tube and starts over, and Mr. Shadetree keeps dumping in more refrigerant until the suction pressure looks reasonable.
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