While AC on, Engine Bogs Down

[Bitsyncmaster]

The readings I got when the compressor kicks off was 25 for the low side and 120 for the high. So I suppose those readings just point towards adding more refrigerant. However, I know I have a leak simply due to the fact I need to keep topping it off occasionally. And the fact that I am using original hoses with 134A. But when I do have enough refrigerant in the system, the AC blows cold. Right now it is blowing cold.

My problem is the sudden RPM drop when the compressor kicks on. Before the new DPI fans I would idle at 775rpm and when the compressor would kick on it would drop to like 550rpm. Big dip! Now with the new fans I would say its only dropping about 100 rpm but still noticeable when at an idle since the engine labors and vibrates. I have tested the ISM, and it is compensating about a second after the rpm dip, and then the rpm returns to 775 like it should. So my idle system seems to be working as it should.

I guess I was hoping I could do something so that I wouldn’t even feel the initial 100 rpm drop at all. Does everyone else feel the engine vibrate the car when the AC compressor kicks on? Is it just the normal operation of the Delorean?

Try turning the curb idle screw clockwise about a 1/4 to 1/2 a turn. The curb idle screw is the lower screw on the throttle arm.

[MrChocky]

The readings I got when the compressor kicks off was 25 for the low side and 120 for the high. So I suppose those readings just point towards adding more refrigerant. However, I know I have a leak simply due to the fact I need to keep topping it off occasionally. And the fact that I am using original hoses with 134A. But when I do have enough refrigerant in the system, the AC blows cold. Right now it is blowing cold.

My problem is the sudden RPM drop when the compressor kicks on. Before the new DPI fans I would idle at 775rpm and when the compressor would kick on it would drop to like 550rpm. Big dip! Now with the new fans I would say its only dropping about 100 rpm but still noticeable when at an idle since the engine labors and vibrates. I have tested the ISM, and it is compensating about a second after the rpm dip, and then the rpm returns to 775 like it should. So my idle system seems to be working as it should.

I guess I was hoping I could do something so that I wouldn’t even feel the initial 100 rpm drop at all. Does everyone else feel the engine vibrate the car when the AC compressor kicks on? Is it just the normal operation of the Delorean?

My car does shake a bit at idle, A/C or no - although less so after changing plugs etc. My problems are different, but I'm reading this with interest just to see how everything is interconnected. My next task is to change
vacuum hoses, but you might be interested in the commentary:

http://dmctalk.org/showthread.php?18...rt-up-behavior

[Trstno1]

Try turning the curb idle screw clockwise about a 1/4 to 1/2 a turn. The curb idle screw is the lower screw on the throttle arm.

all 3 brass screws are closed.

[Trstno1]

My car does shake a bit at idle, A/C or no - although less so after changing plugs etc. My problems are different, but I'm reading this with interest just to see how everything is interconnected. My next task is to change
vacuum hoses, but you might be interested in the commentary:

http://dmctalk.org/showthread.php?18...rt-up-behavior

I appreciate the reply. I've definitely been down the vacuum line rabbit hole. good luck!

[Trstno1]

Try turning the curb idle screw clockwise about a 1/4 to 1/2 a turn. The curb idle screw is the lower screw on the throttle arm.

My apologies......I misunderstood what you meant. Before, the only way I messed with the idle was when I was messing around with the brass screws. I'll attempt turning the curb idle screw when I get home. That will just raise the idle ever so slightly so I don't notice the 100rpm dip? Essentially idling at 875, then dipping down to 775 for a slight second when the AC compressor kicks on? If so, your ECU will essentially do the same thing right?

[Bitsyncmaster]

My apologies......I misunderstood what you meant. Before, the only way I messed with the idle was when I was messing around with the brass screws. I'll attempt turning the curb idle screw when I get home. That will just raise the idle ever so slightly so I don't notice the 100rpm dip? Essentially idling at 875, then dipping down to 775 for a slight second when the AC compressor kicks on? If so, your ECU will essentially do the same thing right?

No it will not change the idle from 775 unless you adjust it to far. What it will do is make the idle motor run more closed but you want to have that adjusted closer to where it will still hold 775 on a hot engine with the idle motor almost closed. I adjust it on a hot engine by turning it clockwise until the idle RPM goes above the 775 then back it off a little.

My ECU you can set the idle RPM from 775 to 1000 RPM.