Alright I have searched on this for 4-5 days and come up with nothing. My car will not idle any lower than 1500 rpm. I have adjusted the TPS to specs using the LED method and the multimeter method and I have no vacuum leaks.

The car starts up normally going to 3k, warms up, drops to about 2k and bounces bewteen 2k and 2.5k for a minute or so then idles down to 1500. No matter what I adjust I can not get the idle lower than 1500. If you touch the gas it will bounce between 1500-1800 before it settles back down to 1500.

I thought that maybe it was the BAC, so I disconnected the BAC to see what would happen and its exactly the same, nothing changes. I have new plugs, wires, fuel filter, etc and I'm getting like 10mpg on an UNMODIFIED S4.

I'm all out of ideas.

 

Have you re-adjusted the throttle stops? Checked timing?

 

damn that sucks...

I've had my share of idle problems that stemmed from every random thing imaginable.

First my return line was clogged which caused a bunch of stupid crap problems.

Second my primary butterfly wasn't synced propperly...was open way too far at idle.

Then I suffered from a large vac leak right after the afm.

IIWY, I'd go over the intake tubing from the Afm to the throttle body and make sure there's no leaks there.

 

have you ever pulled the throttle body off? i had the same problem and when i pulled the tb off and put it back on the cruise control cable was tightend too much holding the plates open. also check to make sure the thermowax idle pin is working right.

 

Have no clue on how to go about readjusting the throttle stops. For me the FSM is a little obscure, care to elaberate?

No I have not checked my timing, thats one thing I need to do.

 

Checked my AFM and associated hardware. No leaks. How do I go about syncing the butterfly?

 

Loom at the rotating assembly on the throttle body...turn it by hand to open it. Then, when you close it, you'll see an arm attached to the rotating assembly hit a screw attached to the mount (or the screw may be on the rotating assembly and the stop on the mount, can't remember)...it's basically what the throttle rests on at idle. It's the crudest way to adjust your idle.

However, this won't effect your economy I don't think, unless the TPS is set impropperly...I'm not even sure if that would change anything.

Oh, another thing that was screwing with my economy and idle...VERY VERY leaky injectors.

 

Mine was tweaked from something, shaft was fucked up...I don't think there's actual way to adjust it. I had to replace mine...It as a visual thing to see because looking into my throttle body it was open like 1/4" at no throttle.

That wouldn't really effect your mileage either. I think you have a fuelling or electrical problem...not mechanical.

 

Cool, thanks for the description man. Is this on the front or rear of the throttle body? I've noticed alittle bit of wet around one of my secondary injectors but can't tell if its just the lube from installing them. I doesnt look like its even getting the metal around it wet.

 

I hope it's not mechanical, I 've only had this motor in the car for about 1 week. Getting 70 miles to half a tank of gas sucks, and I shift at 3k.

 

Id be looking at a misadjusted throttle cable or cruise control cable before anything else

 

simplest possible explanation...didn't think to mention it. There should be just a little bit of slack in the throttle cable at idle...just enough to wiggle the cable...same with the cruise cable if you have it.

The idle stop screw is on the backside of the throttle body, IIRC.

There should be no wet around any of your injectors. If it IS wet, use some B12 or scarb cleaner and spray away any residue there. Then drive and check back on it later...if it's oily or wet again, it's time to send those injectors off.

 

Idle with cruise and throttle cables removed is exactly the same.

 

I've got some break clean and I'll spray them tomorrow before the ride to work.

 

I'd first check the thermo injector release sensor. It tends to stick if the BAC,
ACV, thermowax, CAS, and TPS are not alligned. If not, go to the Vaccum thermosensor, by the right side of the battery, its the green female check input, plug your nuero release bypass receptor into, don't cross the leads, and watch what the check engine light does. Thats a clear indication as to the release module.

PEACE THE DOG

 

Sounds like thermowax or something in the accelerated cold-start system is acting funny.
Clogged coolant passages to and from the thermowax on the throttle body can cause this also.
Bad thermoway will cause this also.

Your bad mpg might not be associated with this problem.
Check your O2 sensor or even swap it with a good, new one if you have no idea how old your original O2 sensor is.


-Ted

 

If the car was running right and idling right prior to this problem, and you have not done any work on the engine recently before this problem, then you might suspect the bac valve sticking open. Remove the bac but leave the plug connected.

Get some carb cleaner. Turn the key to ON. The bac will vibrate. Spray into the bac and let the fluid sit there for a minute or so then dump it. Repeat several times then reinstall the bac. Start the engine and see if this helped. NO? Then it's something else.

 

no he said the cold start system was removed...