Awkward AC issue
 

i posted about this before and thought i had solved the issue. But those were just dreams. my 240d will feel sluggish and accelerate super slow while normal driving. only after i turn the AC knob from the off position to 50% on, will i suddenly regain all my power back. it is so sudden and apparent that i thought it might be something with the compressor. so i cut off the belt to see if it would help it but still the same. i bought the car knowing the AC was not working and i dont need it to work at all. i am ready to disconect whatever i need to get my power back

what in the world can cause this. what else gets turned on with the AC knob? any vacuum elements. could my lost power somehow be connected to my Vacuum leak?

I beleive your 240D has an electronic ac switch correct? The switchover valve on the firewall has a vacuum line running to it. My guess is that you are losing vacuum some how at the switch and the only thing related to power and the vacuum with the engine is the EGR valve. I would plug the EGR valve and make sure it is closed all the way. They can get gummed up and even with the lack of vacuum to close it, they may not close all the way. Just my .02 worth!

my 240D has a round dial as a switch. i dont think it is electronic as you said, but i could be wrong. when i turn the switch in the off position, i can hear a slight hissing. i was thinking vacuum, but i did not know what vacuum devices other than the IP can be affected by it. i forgot about the EGR tho, and i need to look where it is. i though EGR were only found on turbo models. i disabled my EGR in my 300D, but not yet in my 240D.

If you can hear hissing, then there is definitely vacuum moving around. The only thing it really could be, if you cut the correct belt of the AC compressor, is the EGR valve, i believe. I know alot of people put BB's in the vac line but if the EGR valve is sludged up, it wont close. I would bet that is what it is. BrianCarlton makes an EGR block off plate "for testing purposes only" of course, but I am not sure if it will fit the 240d. I have his kit on my 300CD. You could always pull the EGR valve off and clean it to make sure it is closing, then block the vacuum to it so it won't open. Try that and see what happens. Good luck!

i have one of Brian's kits, but seriously did not know my 240D had a EGR:o
i though i was pretty sure that the vacuum lines did not go much past the IP in the engine compartment.

how long did it take you to install that kit on your CD?

I may be wrong on the EGR, I am assuming it has an EGR. I saw you posted earlier about this issue and I noted a sense of desperation. Just trying to throw out some ideas.

Took me about an hour cause I was going slow. I wanted to make sure the copper washer was on there good and sealed. I did not have a torch or heat source as suggested per the instructions but mine has been on there 2 or 3 months and I have no leaks. Just follow the instructions on tightening the ring back around the copper/brass washer and make sure you let your car set 24 hours after install so that the silicone has time to harden.

It could very well be the other way around. Your gaining power due to a vacuum leak. I could only think about the shutoff valve. Maybe vacuum is leaking through the switch and actuating the shutoff valve. If your using vacuum for the ac .....my 2c

I looked on a diagram and it does appear 240d's do have an EGR. I would check that and the switchover valve the previous member posted. A good once over of all lines probably would not hurt anything.

ya i will get out there and check it out. thanks for hte replies so far, will get back you guys soon.

ya so my 240D does not have an EGR. i have the engine block, with the exhaust and intake manifold and the air filter housing above it and that is it for the passenger side of the engine compartment(well the battery).

the only vacuum appliances that need vacuum lines are:
1. the back of the IP which is the fuel cutoff vavle.
2. the top of the IP which is hte ALDA.
3. the cruise control, which i know is busted, and i will disconnect it.

the rest of the vacuum lines go into the car cabin, and are the doors (2 yellow lines), a brown line and a green line (which i though go only to the ignition switch)

i will take my magic boost switch out of the console and see what all is connected and how.

could that switch possibly have anything to do with my blower motor, on the passenger side. i am trying to find every possible part that could be connected to this switch.

green line is ac, brown is cutoff switch. whats a magic boost switch?

art,
your 240D doesn't have an ALDA (no turbo, no ALDA). you have an ADA. Can't imagine how vacuum plays any part of that.

You have a stick, so no tran vacuum modulation.

You say there is no EGR on your engine.

Given the above, I can't see any part that vacuum could play in power for your situation; but I could be missing something.

Just to humor me, pull the heater/A/C blower motor fuse, test drive and give us a report. ;)

i will try that in the morning. i need to know what ALDA and ADA stand for. soo since the vacuum line going to the AC is not needed, i think i will plug that up for the time being. tomorrow i will also use my Mityvac to find out where my vacuum leak is comming from. i suspect one of the doors. i will let you all know what i find out tomorrow.

My bad, looks like the 240d's had EGR starting in 81, you lucked out by one year. Basically, the ALDA is an over boost protection device only on turbo cars.