foild

hey guys

everytime i take my foot off the gas, and let the RPM drop, it goes below 750, right to the little line on the bottom of the tach, and then bounces up to 750 again, and holds fine. This happens mostly all the time, sometimes it goes lower than others.. and sometime it seems pretty good (i.e. nothing to worry about)... but it gets a little annoying.. especially if you are revving your car for fun (i like my car alot.. ok... lol) and everytime it drops off and makes you feel like you are gona stall the car..


thanks alot guys.. any input is appreciated.

cam

HAILERS

Warm the engine up FULLY. Then while it idles, pull the electrical plug off the bac. If the engine dies or almost dies, then I'd suggest the idle needs to be set properly to the free online fsm. Fuel Section.

foild

sorry guys... i cant find a online manual... iluvmyrx7.com is out of order...

can someone explain the procedure for the above???

hugues

This MAY help you:

http://www.geocities.com/huguesdc1/faqidle.html

For online manuals,
look at my links page on my web page in sig.

hugues-

Street Racer

your car's fine, everyone i talk to, their cars do the same, nothing to worry about dude, it's normal....

Bob_The_Normal

I would make a guess as to a not stuck but dirty BAC valve.

Would explain the delay, but wouldn't show up as not working when you unplug it.

Anyway, I'm just guessing 'cause of how things are put together... never taken the BAC apart myself anyway.

--Gary

ilike2eatricers

You should its super easy. You dont even have to remove the coolant lines from the passage if you can undo those screws. Mine werent rusted or anything so it was a snap.

http://1300cc.com/howto/how2/bac.htm

therotaryrocket

What does the bypass air control valve do? And hey street racer, you think these cars did this brand new? So why should it do it now? Maybe it's fine in your sense, but obviously not his, I don't mean to be a dick.

Street Racer

my car does it, it drops to 650rpm sometimes 600rpm and creeps back up, it's nothing completely serious to worry about, if it bothers you, fix it, if it gets really bad, fix it, if you could care less i'm sure it's nothing to worry about, if it's an easy clean-up/fix, then fix it....

uRizen

iTrader: (2)

I cleaned my bac, injectors, ACV, and alot of the electrical connectors in that area first. Then I went about readjusting the TPS, and opening the secondary throttle plates ever so slightly to keep my idle at 700rpm, and mine doesn't do that after all that stuff (did it at the same time, so I couldn't tell you what changed it, probably the plate adjustment).

Now when I rev and let go, it'll drop to ~800rpm, hold for a split second, and drop to 700 rpm. The only time it dips now is if I have my headlights on and then step on the brake while pushing in the clutch.

HAILERS

There's NOTHING normal about the description given. Fix the car.

Bob_The_Normal

I just wasn't being that harsh.

--Gary

endless551

I unplugged my BAC valve during idle and nothing happens, no rev drop nothing, so I clamped the hose below, nothing too.. what am I facing here..

twistedriver

THe dash pot system is suppose to slow the throttle plate closeing. So there is no rpm dips on decel. Sometimes the dash pot would get stuck if is too old and dry. Try sparying some lube on it and checking the vacume hose that the dash pot is connected to.

ilike2eatricers

dashpot adjustment

http://1300cc.com/howto/how2/dashpot.htm

Thanks again to scott89tII for the write ups.

hugues

Put some "heavy" elec load on the engine and then unplug the BAC, the rpm should drop.

if it does not, the BAC system is not working and has no effect because the idle is not set correctly.

About the dashpot, I don't have any and I don't see any rpm dipping at all. So I doubt the dashpot is the root of your problem although it could certainly help to have it adjusted to come into contact above 1,500 rpm (I think FSM says 2,100 rpm).

The above is just my 2 cents and should be taken at face value especially if not an s4 NA.

hugues-

Crionics

ya, dashpot i more of an afterburn device helping to prevent backfires and stuff. Sounds more like BAC.

hugues

I meant to say:

if it does not, the BAC system is not working OR has no effect because the idle is not set correctly.

another possible problem is the TPS, btw.

hugues-

foild

unfortunatly.. that write up for the BACV removal/cleaning is for a turbo..

is it the same for a NA???

do i need to purchase a new asket from mazda, or can i just high temp gasket it?

hondahater

iTrader: (2)

Well I am having the same problem and I have no emissions and no secondary throttle. I'm thinking it is either the charging system or mine is worse when the car is colder. Usually I let it warm up to operating temps before driving it like 5 to 10mins of warm up however the other day I didn't have time so I just let it warm up about 3 or 4 minutes and the first time I came to a stop it actually stalled but after that it didn't happen again. I'm thinking charging system because my idle stays around 740-748rpm however when my lights are on when I rev the engine more the lights get brighter??? Anyways just thought I would mention what I've seen so far on the problem.

MAX-IMAL

Just get a SAFC, mine did that but because I disconnected the BAC need to block it up, any way with the SAFC you'll have a very stable idle.

hondahater

iTrader: (2)

I've got all that

Bob_The_Normal

If your alternator was pulling too much resistance it'd do that hondahater.

Wish I paid more attention in class on rebuilding alternators... only auto class I took and I can't remember jack. ;D

But yeah, I don't know where else to start on that except that maybe somehow the alternator or the belts to it are getting too much extra friction, or the alternator is just going bad.

--Gary

ilike2eatricers

If you have to use the SAFC to get a stable idle I think you have more things to worry about that spending more money on go fast goodies. A car should have a stable idle without an SAFC unless you have some crazy port job.

hondahater

iTrader: (2)

thanks bob! I have a dual alternator pully I wonder if that is what is causing it? Or at least causing the lights to brighten when I rev it. huh? I may just go get my alternator tested but damnit it's such a bitch getting that thing back on. I have to use a big *** hammer to knock the alternator onto the spacer at the same time trying to line up the holes right Anyways I don't think I'm going to worry myself with the issue to much because as soon as my car warms up it works fine (of course this may change if the alternator is going out).