Flyby116

When I start my car like normal goes to the 3000RPM then drops to about 1500-1000RPM and will sometimes start to bounce between them two...And then once warmed will go to normal about 750-800RPM and sounds great but once I say put on the air or even the lights, anything taht uses power will make the car start to die and I have to hit the gas... But it will drop to like 200RPm and then I can save it so I think it shouldnt be a big prob.

But what would this be??? Everthing else in the car is perfect my engine only has 21,000 miles on it.
So maybe a tune up will help?

Thanks guys.....

clarkrx7

Well, sounds like you have some sort of BAC Problem no I have not had your problem but from what I have read the BAC speeds up and slows down do to Draw on the engine. Such as A/C or shifting in to gear to Alternator. This may be your ECU not sending it to the BAC do to the fact that your car runs without surging up and down on Idle. What do you think HAILERS?

SpeedRacer

Sounds like BAC to me. To temporarily fix the problem, just raise your idle a bit. In the meantime pull out the old Haynes manual(or Mazda Service Manual if your lucky) and read up the BAC valve. There is a REAL easy way to check to make sure it is working, but I can't think of it off the top of my head, and my Haynes manual is at home and I'm at work.

doklen

i do have the same problems, i have pulled, cleaned and checked my BAC, everything seems ok. What is the voltage supposed to be at the BAC? the test says to apply 12vdc and listen for a click. Well i checked my voltage going to my BAC and is was 10.3vdc w/o ac on and 10.5 w/ ac on, the voltage is constant. So im thinking that my ECU may be bad. Can anyone give me the voltage they have? i got a 91 n/a vert. thanks

HAILERS

DOKLEN... I think your right. I remember checking the voltage at the bac before and after the a/c was turned on and there should, I believe be a voltage drop. There is a site on the web, maybe fc3s.org that has a fix by a Paul Stoaks for fixing an ECU that does not put out to the bac. I've done it myself and the part from Radio Shack cost maybe a buck fifty. Need soldering iron and should buy soldering wick from them also, maybe a buck.Its a transistor that gets burnt up. Thats if that is the problem. I'll look around for the test and web site. I'm at work now. FLYBY116 sounds like his bac is disconnected or not working. I'd suggest going to http://www.iluvmyrx7.com and download section 4a or 4b of the factory manual and read about the bac. Dave Gibson who writes on this site own the site fc3s.org and on his site you can down load the factory manual also. You might go the SEARCH on this site and put in the name Dave Gibson. Look at on of his posts and I believe you can click on the fc3s.org logo.. not real sure about that, think so.At work.

HAILERS

I just looked....http://www.teamfc3s.org/main.shtml is the site. I open it and it has some writing on the opening page that says if you have problems with this site go to the old one. I clicked where it said go to old site. On that page it has a listing for ARTICLES. I clicked that. Then there is a listing that says DIAGNOSING AND CORRECTING TURBOII IDLE PROBLEMS do not let that scare you n/a folk off. Now near the bottom of the article it tells how to determine if the ECU signal to the BAC is good or not. Also if bad, how to repair. Cost about three bucks if you have a soldering iron already. Not hard to do. I did. Living proof.