it does the usual rotary warm up at 3k rpms jumps down to about 1100 or so stays there but after driven or rev'd a little and warmed up it will not hold an idle... i just got the car for a decent price since it needs some body work but engine runs strong and pulls all the way thru w/ not much hesitation that i notice yet... did notice it has headers on it and an intake but! the o2 sensor is just plugging the hole and not doing anything because its not plugged in... can this cause a bad idle? tried looking for the plug to put it in but i cannot find it... any pictures or point me to diagrams of a 1990 GXL... thing is tho its not throwing any codes either... if the o2 isnt causing the car to not idle than what other things are there to look at.. thanks kinda new to the rotary world... oh and btw yes i did search for about 30 mins and its not fun on 56k

edit...

also noticed this when searching google.com

Rough idle: The idle won't stabilize (varies up and down) unless an orifice is installed in the idle-air bypass valve. (1990)

from... http://auto.consumerguide.com/Auto/U...reviewshowall/

 

bump...? anyone..

 

so i went out and played w/ the car a bit while i was waiting for someone to reply to this post... and i believe it may be because the previous owner had disconnected the hoses on the air pump... and i saw that the other ports were held open with hard wire... my new question is does anyone have any pics of what the air pump is suppose to look like all hooked up and what opens the ports? vaccum on the pump or a cable? as of now nothing is connected to that throttle down there.

 

uh

I'm not that great but try this

Spray WD40 around the engine bay, hoses and such and listen for the engine reving up, if you got a vaccum leak which i think you just discribled it will rev higher, DONT spray it near the intake as that will just rev it up and be a false alarm.

Also if it revs up suddenly spray more then that area and find your problem =]

 

It sounds like the people before you had a blast in the engine bay. The air pump on you S5 used to connect to an ACV (which is probably blocked off now) and power the aux ports that are now wired open/closed. I don't think that would cause your idle problems, but I could be wrong - check for vacuum leaks like cmanns says.

I'm pretty sure the unplugged O2 sensor should be throwing a 15 or 17 diagnostics code on your S5. Did you tap the diagnostics plug properly? Without the O2 sensor, the ECU uses a failsafe value, which could cause rough idle (because it's false), but I think the reason your car dies is different. My first reaction is the idle was set while the car was still warming up (i.e. the fast idle mechanism was still active). Try turning the air adjust screw to see if you can get it to hold idle long enough to properly set the idle and idle AFR (see idle afr how-to – check for a grounded test connector too). If that doesn't help, I believe I've heard people point at the AFM in this situation. In either case you should have the O2 sensor plugged in so the ECU can do its feedback thing, and download the S5 FSM.

My guess with the BAC orifice you quoted is it helps broaden the stability range of the BAC system, but that properly tuned, the orifice isn't needed. Maybe I shouldn't offer guesses though!

edit: also check the TPS!

 

alright guys ill check all that 2morrow in the light... and yes the ACV is
blocked off poorly by what seems to be BOLTS AND SPARK PLUGS... does the ACV need to be hooked back up in order for the 5th and 6 ports to open properly?

 

Blockoff plate held on by spark plugs?! Could they have tapped a spark plug in there to get backfiring? That needs a photo! Unfortunately my S5 experience is limited to what I've seen in the FSM and on the forums, but I know people have routed the air pump to the aux ports without the ACV. Hopefully someone can post the method, but I think the idea is the air pump goes to the stock aux air solenoid, and from there to the aux ports.

 

NO NO NO! lol... even tho that'd be funny. the ACV is still there w/ the hoses hanging out of it and they put a spark plug in the hose and used a hose clamp to seal it off.... i will try to post up pics of what i have 2morrow and see if u guys can help me out any... also! does the little throttle switch on the ACV open the 5th and 6th ports?

edit..
and also the air pump is gone i do not have it.

 

i'm gonna mess w/ the TPS 2morrow as it seems thats what the problem is from the write-up i read... since it is a Fluctuating or oscillating idle...

also if u dont mind... was wondering how i get the 5th and 6th ports to open w/o the air pump or ACV.... as i said before the ACV isnt REMOVED but the all the hoses are plugged w/ spark plugs or bolts and then tightened w/ hose clamps... ( i just ordered the block off plate from mazdatrix.com)

 

Well the bolts in the hoses sound like they might leak, and because the ACV has access to the intake manifold (via the anti afturburn valve), that could mess with idle too. Let us know how it goes!

 

vac leak, tps, afm, timing, bac. check all of that to see that it's working, then put your airpump back on so your 5/6 ports and vdi work again. you'll be a lot happier.

 

with the mess you are describing, i'd say vacuum leak. you definitely need to go through and figure out all they did and then how to block everything off properly. i'd also get pics on here for people to look at.

 

I'm sorry I need to see a pic of this spark plug..... Its blowing my mind

 

lol... yes pics will be posted soon of this horrible job... was also wondering if the ACV and air pump can be removed properly and keep the 5/6th ports functional? since i do not own the air pump any longer and have no intention of keeping it emissions friend in my state.. plus the shooting flames arent so bad...

 

Yes, the auxiliary ports can be made functional without the stock air pump. People use one of two methods:

1. aftermarket air pump
2. solenoid (only been done with VDI so far)

Though it might be best to keep the air pump and just do a little re-routing.

 

thats thing i bought the car like this with everything removed... i do not have the air pump.

i did the idle A/F ratio adjustment today and that helped it out alot... but! it still bogs down lower than 700 after i let off the gas and almost wants to stall... but atleast it doesnt bounce anymore from 200-700

 

my friend has this same exsact problem and i cant figure it out as well. i need to look in to his car more to try and figure things out. his also is retarted. evry time he puts it in to gear it reves higer and then back down. correct me if im wrong but the transmission shouldnt have any thing to do with idle but i donno.

 

could have to do w/ the engine being under a load tho...