Engine bogs down and stalls with A/C on

[jorde]

Recently replaced the old piston a/c compressor with a new rotary compressor. my z runs fine and idles at around 900-1000rpms with the a/c off. after running the a/c for about 15-20 minutes and i stop at a light or the car is left idle rpm drops to about 4-500 and eventually stalls out. don't know if this changes anything but the fuel pump was also replaced and had an electronic ignition installed as well. had the problem before I changed them but it still doing it now. any ideas, please help.

[ezzzzzzz]

On my 240z there is a bracket on the carb linkage to install a simple solenoid. It is energized with the a/c compressor to step up the rpm to overcome the additional load. It has been the same on every carb or early FI I've owned. The later FI's use the ECU to control idle rpm. Since you didn't mention what car we're talking about it hard to assess.

[psdenno]

My solution has always been to just set the idle RPM a couple hundred higher. This worked with both the old York compressor as well as the current rotary unit. Not very high tech, but solves the problem nicely. There's probably some rational reason I shouldn't do that, but it's worked well for 37 years.

Dennis

[jorde]

ezzzzzzz, i'm sorry i forgot that part. its a 1973 240z. i'm not a mechanic by any means,but i just replaced the front fuel pump and filter the other day. is there a chance that it could be the rear fuel filter or pump. initially i thought it was a problem related to the new a/c since i have it on when's happened in the past, being in florida i usually drive with a/c turned on. but today i turned the car on and left it running without the a/c on. i had the same results, it just took a longer time to get to that point when it stalls.

[ozconnection]

Check your timing at 750-800 rpm. Why does your car idle at 1000rpm? Is there an air leak somewhere to cause the engine to run lean and spike the revs to 1000rpm?

If you have purposely set it up this way, the mixtures could be too lean at idle and the timing setup too retarded if base idle timing was adjusted at 1000rpm's. Of course, let the car sit and idle for a while or add the extra load from an AC compressor and the thing dies on you.

Weak idle mixtures and/or retarded ignition +/- air leak. Check your plugs..black rich, white lean, grey spot on.

Good luck with it.

Cheers.

[jorde]

the past few days i have been turning the car on and checking when exactly it begins to sputter and stall. it seems to always happen right at about the time the temp. gauge reads dead center. thats with nothing turned on other than radio. if i turn on a/c or even the headlights, it tends to speed up when it sputters and stalls. it seems that when the engine gets added stain it speeds up the process of when it sputters and stalls.taking it in to a z specialist this week so hopefully he can figure it out.thx for all those who tried.i will keep u informed of what it is.