I have read all the information for rough idle and checked and applied what should be the case. The BAC is working, I can disconnect and jumper to battery and engine increases to around 1100 from 800 idle. The side screw will change the RPM from a high of 1200 down, not sure if it will go below 800 or not if that's important.

1) Timing is set correctly 5 and 20 degrees.
2) Tried two plug sets BR8EQ-14 and BR9EQ-14, little if any difference.
3) Master Blaster 2 coils. I am starting to wonder about this as some say they don't work well with stock ignitors because they are 0.5 ohms instead of 1.5 ohms for stock coils on primary wind. Just reading that some have good luck and some have stumbles.
4) As I said, BAC seems to be working. It runs just perfectly when I jumper out the solenoid. But add the A/C while keeping the coil energized and it falls and stumbles.
5) If I disconnect the vacuum line (small) going to the BAC the engine revs up I believe. I'll double check that, getting kinda confused tried so many things. Either way it changes.
6) Just turning on the lights and radio and moving the electric windows has no affect on the idle.
7) Oddly, some times the idle sits at 1100 with the A/C on then drops back to 800. If I just punch the throttle it goes back to 1100.
8) I have checked to make sure the throttles are not sticking.
9) TPS is set correctly.

The car drives great in every way. Keep the A/C off and it runs fine stop light to stop light. Idle is smooth and consistent. Turn the A/C on and rough idle at times and smooth idle at other times. I'm thining that the smooth idle is when the compressor is on and rough is when it's off, but that's just a guess.

Thanks for reading this far in detail.

a) How do I further test the BAC? Does it seem to be working? I have taken the solenoid off and also removed the BAC. Could not split easily so didn't disassemble the BAC. Sprayed cleaner in and it's operating as long as (I assume) rubber diaphragm is intact.
b) Could the A/C be overcharged causing this?

Thanks for any help. Welcome any questions.

Jim

 

Here's a very short video of the drive to work showing how it drops at a light and punch the throttle and it jumps up and stays.


https://www.yousendit.com/download/Q...Zy81bmowZXNUQw

 

the BACV may be working but may be dirty. its worth ordering a new gasket and ensuring that its clean internally and that all vacuum ports are properly cleaned.

 

That screw that you are talking about is for A/C purposes. When the A/C compressor clutch engages, your idle should not drop below normal idle. I always adjusted mine so that the idle is about 900-1000 with the A/C compressor clutch engaged. Can't remember what the manual says.

 

I'll get the BAC separated, maybe a knife between the two pieces will cut apart the old gasket, it's stuck hard. I'll report back on the results and will also set adjustment in the 900 RPM range.

 

Decided to swap coils leading to trailing to see if the leading was the problem and the leading is leaking oil. This can't be good. These were added by a local shop back when the car was flooding so badly. Bad move on their part as they maintained the horizontal mounting completely against the MDS site instructions.

Bought 2 Mazda coils NOS and the stumble is gone. I won't call it "brand new smooth" but hardly a rumble at 800-850 RPM. Runs much better now on A/C also, I adjusted the BAC to 900. Still going to recharge the A/C to see if it's overcharged.

 

glad you were able to figure the issue out!

 

Now have the idle more refined at 800+. Tried several plug configurations from stock 9's to 8's and settled on the B8EVG at 30 thousands gap. Tried 25 and 35, 30 being the smoothest idle. Here's a video showing the current status with AC off, on, off.

https://www.yousendit.com/download/Q...U1BCSWRvSWNUQw

I also checked the AC charge. 70 on the low side, which is high. Now have that at 30 which is borderline low. Lowering the pressure helped the idle very much also. Vent temp after a drive is 41 degrees so that's not horrible, of course, it's PA and not Texas. I will be completely evacuating and refilling with Freeze-12. Charge was R134A by previous owner so I safely vented.