Hey guys..Happy New Year...
Ok.heres my problem; i have 88 vert.n/a;stock except header,cai and catback.....whenever i set the time; leading and trail marks lined, i can not get it to idle at 750-800.
its at 1-1.5k.The only way i can get it to idle is to retard the timing..i set tps, mixture, all to no avail...is it possible my bac took a dump? thanks for any and all suggestions.
GREAT forum bytheway...

 

how are you reading the rpms? the stock gauge is off about 200 rpms or so, have you installed the intial set coupler before adjusting the timing/idle? another possibility is a vaccum leak, buy some carb cleaner at the store and spray it all over the engine if the idle fluxuates when you spray it on certian hoses/areas you've found a leak

 

Well, if you suspect the bac ......pull its plug off. That might make a difference. IF not...then remove the bac. Buy some gasket paper from PepBoys and cut out a gasket but don't cutout for the large hole. Just the two holes for the studs that hold the bac on. What you have now is, is a blockoff plate of sorts. Install the bac with its old gasket and the new one you made(no big hole, remember). Now start the car up. Does it act the same or not?????? If it acts the same.....it ain't the bac. If the thing idles lower now than before....remove the bac and let it set in some fuel injector cleaner overnight then blow it out and reinstall it and see if things get better. You should connect 12v and a ground to the bac before reinstalllation to operate it when it still has some fluid in it. Just touch the positve 12v for a split second or so while you do that. OR.....invert the bac with fluid in it. Connect the bac plug to it. Turn the key to the car on. Most likely the bac will vibrate and that will give it some cleaning action (bac is not attached to the engine doing this. Just lay it on a towel with the elec plug attached to it.)

Your problem could also be other things like the fast idle cam/thermowax out of kilter. How long has it had this rampaging *idle*?????

 

isuspected the bac.because when i unplug it it doesnt change anything...idle at 750 w/ timing retarded..havent checked thermowax for proper operation.....thanks for input...will reply w/ results

 

well it started about 3 mos. ago i never paid it any mind til i gave it a tune up and stumbled across this problem.
ill try the bac trick.see what happens..thanks for the advise....no my plug wires arent crossed...just thought i mention that

 

If the idle is as high as you state...then removing the bac plug will have no effect. That is a normal thing. What can happen with a bac is that it *seems* to not close all the way during its cycles and that causes a high idle. Cleaning it will let it return to its normal operation.

Then again there's no reason to think its just your bac. It could be the things described by BLACKR7. Give 'em a try if the bac does not work out.

I had a dirty bac once and it acted similar to what you describe. What happens ....if the engine speed gets up around the 1100 range....is that the timing advances and the speed will jump up a couple of hundred rpm seemingly all by itself. I remember doing a little trick at that time. I'd turn the key off real quick...let the rpms drop down then flick the ignition back on before the engine died. When I did that the idle would go close to normal and stay there. Then I judiciously applied throttle and notice how the rpms jumped at approx 1100 rpm to something higher. At that time the rpms would not return to a normal idle unless I repeated the process...turn key off....let rpms drop...flick key to on...then it'd idle around normal 750. Cleaning the bac fixed this problem to date, about six months now.

Normally I would not mention the bac and just say get a can of starter fluid and spray around the hoses looking for a vac leak. Also if that did not help, take a look at the rigging of the fast idle cam/thermowax.

 

i will check all the above, beginning w/bac as soon as i get a break in the weather...its like 25-30 here in Delaware..thanks for the input guys.