So my car has a rough idle.. and i was doing some reading

and i was wondering if i remove the bac valve and then adjust the idle if that would fix the problem..
because when i first start the car it runs pretty good. then when it warms up its a low idle.. and sorta is ruff and low?
didnt know if this would be a temp fix untill i got a new bac valve andput some new hoses on it.. because i think its leaking air or somthing??
idk for sure!?!?!?

 

I just finished removing all emissions/EGR/BAC/TB mod. My car ran good before, but it runs absolutly wicked now. If you can i would remove all this useless stuff and do a 60k tune up then it should idle solid unless you have a stuck seal or something.

-Ben

 

removing the BAC and putting it back on shouldn't do much...the idle can only be adjusted through the BAC on turbo models as far as I know. You can raise the idle from the screw on top of the throttle body until you figure out the problem.

 

yeah well i know where to adjust the idle and stuff.. and i was reading some people didnt think it was a good idea to get rid of the bac, but i figure it wouldnt hurt... so ill prolly keep it off..

lol yeah i hope it isnt a seal...

if it is how much those usualy cost to replace and is it alot of work?

 

The BAC valve is not useless, nor will removing it make your engine run any better. The only way removing emission controls will make the engine run better is if something was broken before and making it run badly and/or you removed clogged cats.

 

so say if there is a leak from a hose or somthing on the bac valve? would that cause a rough idle? because i saw some hoses for sale like 10 bucks... and didnt know if i should just do that?

 

Rough idles have two main causes: TPS out of adjustment, or vacuum leaks. 9 times out of 10, it's both.

 

Aaron is right. More often then not it's because the TPS is out of adjustment or you have a vacuum leak. This is when you're talking about a rotary. On most engines, the IAC valve is to blame most often. I've got all the same things removed too. My car won't idle correctly when it's cold, but after it warms it idles very smoothly at 700 RPM after I made some adjustments to the intake screw, idle AFR sensor, and TPS.

 

Don't rule out the possibility of low compression on one or the other rotors. Also read this writeup:

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/rx7-rough-idle-diagnosis-simplified-645051/

 

I don't agree with all the people that remove their thermowax and BAC valves. They are there for good reason.....stable idling under all conditions. No power increase can be obtained by removing them, and it doesn't take up much room, so why bother?

 

sweet.. thanks for the link ill have to try that out. if it is compression then that means ill have to replace a rotor right?

 

If it's low compression, a teardown and proper inspection of parts will be in order.

 

dang.....
well lets just hope its a vac leak or somthing..
or the idle needs adjusted

 

Honestly, don't take this the hard way, but even if you don't agree with people removing them, don't bother speaking up about it. All it will start is another thread on what is "streetable" and what isn't. Yes, there are gains to be had with removing it, such as more space in the engine bay and less weight, along with less things that could go wrong in the engine. I agree with you though, more often than not they are best left in there to produce a stable idle and an easier cold start, but keep in mind that the car can run perfectly well without them. I have them removed and though it is a pain in the *** for the first couple minutes driving the car in stop and go traffic, after the car is warmed up it idles and runs like a stripe-assed ape.

 

lol cool.. i wasnt trying to start contraversy.. lol i just didnt know and i wanted to know what people thought.. so i could take the best action..
but i think im gonna tamper with the idle controle and if not then im gonna go with removing the bac valve.. if there isnt a vac leak!!!

 

No, no, I was talking about what scrip7 said. Removing the BAC will cause the car to idle funny or not at all until you tune the idle a bit. Like Aaron said, it's most likely the TPS bad/out of adjustment or a vacuum leak.

 

lol alright cool..

well hopefully the TPS just needs adjusted..

 

Yes... I am having problems with these silicone hoses I bought... They are shrinking and coming off and causing my idle to be ****... Or they get squishy and collapse under a vacuum... Either way my car idles like crap when it happens... I plan to replace them all this weekend with normal rubber line...

If it is that silicone crap... Absolutely not... If it is good old rubber hose, absolutely... : )
And like Aaron said... Adjust your TPS... Mines bad and I am waiting for the replacement to come in... I adjusted it the best I could for it being broke and noticed a major difference...


I hate to say it but people in here are way to quick to jump to the "REBUILD" theory... If it does not run right it must be low compression and we need a rebuild...
If I rebuilt everytime I came in here asking for advice and was told to rebuild, I would not put a full 1k miles on it before rebuilding again... Listen to Aaron... You probably should replace all vacuum lines and adjust the TPS...

Can this be put in the FAQ...? I mean it would have helped me more than once...

 

what do you mean Low idle? stock Idle , A/C off should be at 750 RPM's I've had my BAC up until I went to a E6K, & now, when I add A/C again. Check for a vacuum leak, it wouldn't kill you to just replace old crusty lines anyway. TPS out of wack, is bit more involved, but really not impossible. Plenty of write up on how to build a tester. I would really try these before anything else.

 

yeah deff.. i been reading the sweetest manual on rotary, but im gonna check out for vac leak.. next pay check im just gonna replace on the lines anyways.. see how that helps.. if it doesnt fix then might play with the TPS.. guy before me took it to a race track in Circleville so he might of played with it..
Just gotta see how it works out!

thanks for the help guys... this really answered my question thoroughly

 

Amazingly, it's already there. Has been for years.

 

We have a FAQ? since when?

 

its like right in the at the top of the rx7 second gen forms.. i believe!?

 

December 2005...