Rpeck

I have the BAC completely disconnected right now.. it does not seem to change things at all .. plugged in, or unplugged. So i have it unplugged right now .. to just eliminate that as a problem.

biorotary

if it's "stuck" open, unplugging it won't matter, because it will still be open. to completely rule out the bac, is to clean it then test it to make sure it closes all the way and opens when "power" is applied...then put it back on...

rob, when you set the initial jumper, does your idle drop at all?

Rpeck

I does drop a little bit it seems. I have taken the BAC off and sprayed it good with cleaner, I redid the connections on the end of it also.. I put in a new BAC gasket, and i hooked aligator clips to my motorcycle battery .. and touched the conections to make sure it clicked & did its thing .. everything looked okay .. I also Ohm'ed it out and its within spec .. So I think my BAC is fine.

biorotary

have you messed with your your afm adjusting screw at all? if it's been tampered with, it could screw things up...
my dad was messing with mine when i couldn't get the idle down and it totally messed up my afm reading at the ecu both at idle and when driving...
just a thought...

Rpeck

No, I havent touched it ... I didn't even know that a S4 had one .. maybe I should check that out .. is there a way to make sure it it set properly? can you ohm it out .. or check the voltage or anything? ... My S-AFC does seem to show a accurate percetage reading on it though ..

Rpeck

It's bugging me that .. it does not go back far enough to hit the throttle stop screw.. I think maybe somthing inside is fugged up. I will be taking the manifold off to install my new 720 primaries I just got ... but I can't do that until I smog it .. so i was hoping to correct this .. smaog it .. then take off the manifold. But it looks like I might have to do it twice It runs great .. and holds a very steady idle .. it doesnt bounce at all .. but its just to damn high ..

biorotary

i don't know how to mess with it properly...and i've heard many people on here including reted, hailers, and keith all insisting on not messing with it, but when my dad messed with it (turning it counter clock wise), my car ran like crap with a very unstable idle with lean reading from my a/f gauge so then i decided to turn it clock wise all the way until it wouldn't turn anymore..and now it's showing a tad bit rich at idle. but until i did that, when i ran it the other day, my a/f gauge would be way off showing lean when there's any boost and now i'm getting stoich and rich depending on the boost level all the way up to about 12-13 psi.
i still don't recommend you messing with the afm, but if you have an extra one (the one from your n/a would work) you can swap it out and see if it helps with the idle...
just a thought

Rpeck

Thats a good point my Idle is rock solid 800 RPM's on my N/A .. i could swap that out and see if anything changes. I will prolly try that before I pull that damn upper intake off again. The pain in the *** of all this .. is. I will have to do it all over again in a coupel of weeks. Right now I have the stock exsaust, intake & ecu chip in the car .. It will all have to be retuned once I put my aftermarket stuff on ... Damn CA! hate the laws love the climate.

biorotary

haha..that's why i'm here...there's other reasons too, but this really isn't the place for it...look at the av and you'll know what i mean

RETed

Be careful, the EGT's are hot enough to give you a reliable O2 reading at idle...


-Ted

HAILERS

To really understand the fast idle cam etc you NEED to take the throttle body off a stare at it.

That said, take the intercooler off. Now you know where the throttle stop screw is, you described it. Short, jamnut of 8mm socket size holding it. You said the linkage is not touching it. Right? Right. Now look 2inches outboard from that screw and you WILL see the head of a screw. That is the CAM ADJUSTING SCREW. What it is NOT, is the fast idle screw.

So, take your finger and get under the flange that the CAM ADJUSTING SCREW is going thru, and LIFT UPWARDS and release. When you did this, did the linkage come closer to the STOP SCREW???? The one with the 8mm jamnut???? If it did, and the engine was hot, then the fast idle cam is not coming off the roller.

Its possible that your not getting enough flow thru the throttle body to heatup the thermowax. If it does not get hot enough, its plunger will not extend enough to drive the cam off the roller. If the cam does not come off the roller, the throttle plates will be cracked open a bit.

I have to admit, that if you did not munky **** with the screws and linkage while doing the rebuild, and the idle was good before the rebuild, that this should not be your problem. Take the throttle body off someday and pour boiling water over the body of the thermowax and you'll see how the darn thing works. Look at the manual and the pictures in the fuel section. Its under INTAKE AIR SYSTEM. Pictures etc.

Don't confuse the fast idle screw with the cam screw and the throttle stop screw.

The new radiator cooling real good with a cold thermostat might be adding to your headaches. Just a thought.

P.S The part above where you lift up on the screw/flange and release it........when you do this, you release the cam off the roll pin. See manual for illustration. Have fun.

HAILERS

Just another thought. If during the reassymbly, you did away with the water hose at the bottom of the throttle body(you know, the one that makes life hell), then the thermowax isn't heating up and extending. That would explain why there is a problem now and not before the reassy, if the hose was there before. Gotta have water flow thru the throttle body for it to work. No crimped hoses allowed either.

Rpeck

Great info ... I am not sure how it was idleing before the rebuild. I bought it with a blow rear apex and trailered it from Oregon to CA. I did leave the thermal hosed for the intake hooked up .. but I DID replace them, I used my own hose and I used a hose with a 90 deg. bend to try to avoid kinking it. I will double check and make sure it is not kinked. The car is running really cool … I am pretty sure if memory serves me .. they had a 165 180 and 190 degree thermostat for this model. I put in the 180. But the temp gauge does not ever exceed about 1/8th .. it does about 2 mm above the C line. I wonder if this thing is my problem. Is there a way to disable it? What are the ramafacations of diabling the high idle gizmo?

Rpeck

Another thought. Now .. when I go for a good hard run … and I let the car sit for 10 mintes or so .. I start it up, it Idles way to low.. it wants to die. But anfter just a couple of minutes its back up to 1400ish. I was thinking if it’s a heat related issue.. do you think when it sits there… no coolanr running through when the car is off .. maybe that thermal high idle thing gets hot enough to trigger … thus the real low idle? But once coolant goes going again it gets to too low a tempature? Would that make any sense? Or am I just pissing in the wind?

HAILERS

Thats a thought. If you knew exactly what and where the fast idle cam and roll pin were, you could get a mirror, small, and with the intercooler off look for the cam and roll pin and see if the cam has come off the roll pin as it should. Or whether it did not come off the roll pin. If it came off, then you need to look elsewhere for the problem.

The low dying idle after a hard run is a sign of a non functioning bac valve. Or if I work at it, it could be a slightly cracked open blowoff valve(forgot the real name) or something else. Just a guesser here.

fcfdfan

Thanks all you guys for this thread. Very interesting reading and relevant to idle problems I'm having on my 87 T2.

Thanks,
Nat

djantlive

I think it could be a lower intake manifold gasket leak. On my FD, the LIM gasket was paper and prone to leaking intake air which causes high idle. Does your idle lower when you are in gear and stays 1000-1500 rpm when you are in neutral? It's probably a vaccum leak some where.

Rpeck

My problem is consistant... in gear or neutral. I don't think its a gasket issue ... at least I sure hope not. It only has about 800 miles on a fresh rebuild .. with all new gaskets. I torqed everything to spec and made sure to clean all the old gasket off completely.


Hailers- That makes sense about the BAC and hot idle .. I have the BAC disconected right now ... trying to narrow this issue down. So you think if my BAC is working right that starting when hot low idle issue should go away? I am going to check that cold cam thing the best I can tommorow nite .. I was to damn tired after work to tear it back down today. I have been driving it daily to work ... trying to get more break in miles on it... run great, other than this bloody idle!

Rpeck

Well im headed out to try to deal with this problem... if anyone has any brilliant ideas of things I should look over while I'm at it .. let me know. I will be checking in periodicly.

Robert

rx-7fc

mine does this too but can it be from the tb mod

Rpeck

For those of you with a similar issue read this post to see how I finally got mine to work correctly;

https://www.rx7club.com/forum/showth...hreadid=124651

rx-7fc

my idle starts out low about 700rpm but goes up to 1500rpm when it gets warm

rx-7fc

bump

Rpeck

Your high Idle thingy may need adjusted the opposite way that mine did .... look at the link above and check out my pictures you will get the idea.

rx-7fc

mine is not a turbo but i think mine is hiting that thing when it is cold so i don't know what it minght be or it might be what you said