RPMs drop: Idle Problem

**eksz** · 10-20-2011, 11:14 PM

My idle is screwed up on my 94ES. Car starts fine. It runs fine as long as I am driving (i.e., giving it some gas) but when I have to stop for a light or traffic, the RPMs start to drop and unless I catch it and give it some gas, the car dies. Ironically the car tends to idle fine when first started (cold engine). When it first starts it idles rock solid at 700-800 RPM. As soon as I start driving it no longer wants to idle. Even with the engine throughly warmed up, it still has the idle issues. When I stop the idle drops and usually kills the engine unless I catch it and most times when I shift into park (auto trans), the engine just dies.

This started happening about two week ago. Prior to this, the car was running fine and I had no idle problems. The idle problem started after I twice left my lights on and drained the battery until it was dead. I know the car is suppose to re-learns its operating settings after experiencing a dead battery but its been two weeks now and is showing no sign of improving.

1. What do what I need to check/fix?
2. Anything I can do to help the car re-learn its operating settings faster?
Thanks in advance

**Galanttuner10** · 10-20-2011, 11:33 PM

alternator could be on its way out or the idle needs to be raised by the biss screw on the throttle body. what is the idle at in drive?

**g-ridda** · 10-21-2011, 04:01 AM

sounds like a vacuum leak or idle air control valve ....it doesnt matter if you wait a year if you dont drive the car over about 40 miles it wont relearn itself

**eksz** · 10-21-2011, 07:33 AM

Battery died because I managed twice in a week to leave the lights on. Since then the battery has been fine (because I haven't managed to leave the light on) which makes me think the alternator is okay. Car was running great untill I managed to kill the battery twice. I'll have to check the idle in drive right after start up. While driving the car idles down to 500 RPM and then dies unless I give it gas.

As far as needing to drive 40 miles to make it re-learn its settings. Is that 40 miles in one go? I ask because I drive about 20 to 30 miles a day so have logged probably 150 to 200 miles since this started. I'll check for disconnected hosed/plugs.

**Galanttuner10** · 10-21-2011, 09:32 AM

I'm leaning towards raising the idle via the bias screw and seeing what happens. Raise the idle 200 rpms in park and see how the car acts

**g-ridda** · 10-21-2011, 10:58 AM

if you havent messed with anything besides the battery do not mess with anything now like the idle screw or throttle cable or anything like that if the car has be running fine theres somthing wrong and its not the idle screw.....when i say 40 miles thats in any type of order doesnt have to be in one go....check you battery conections for corrosion or loose terminals if either is the case it would case to car to always reset the ECU

**Galanttuner10** · 10-21-2011, 04:23 PM

messing with the biss screw wont cause anything to go wrong, it will allow us to see if the higher idle keeps it running or the same issue. when my IAC went i had a check engine light and had to hold the throttle to keep it idling when cold and once it was warm there was no more issue, i want to attribute it to a super low idle as on my 325xi the idle in drive started dropping that low and the car kept stalling. raised the idle and no problem since

**Goku** · 10-21-2011, 05:29 PM

LOL.... disconnect the battery, leave it for about 10-20 min, reconnect the battery. Turn the car on and slowly increase the revs up to about 2000-2500rpm and then slowly drop it off again. do that about 4-5 times, this lets the ECU relearn where the idle is.

If that doesn't work, you're on ya own =D

**eksz** · 10-23-2011, 10:13 PM

So far I have not done anything but the car is starting to stay running when I have to stop for lights or traffic. The idle still drops but now staying between 500-600 instead of 500 and below, I assume the slightly higher RPM is whay it is no longer dying. I'm tempted to adjust the BISS screw to bump it up to 700 or so but before doing that I would probably try GOKU's suggestion of "disconnect battery, leave let it sit 10-20 min, reconnect battery and then turn the car on and slowly increase the revs up to about 2000-2500rpm and then slowly drop it off again. do that about 4-5 times, to see if it relearn where the idle is." Meanwhile as long as it stops dying I'll just watch it and see what happens next. Thanks for the suggestions/help.

**eksz** · 10-27-2011, 11:28 PM

Still haven't done a thing to my car but now it is idling perfectly at 700-800 RPMs and the the dying when I come to a stop has completely ceased. I guess my car is just a slow learner.

**justin** · 10-28-2011, 12:40 AM

Maybe throttle body itself EGR valve or TBS sensor most likely go to the junkyard get another throttle body like 15-20bucks or less.. Clean it and then switch them and c what happens.....

**Goku** · 10-28-2011, 05:51 AM

If it happens again, try what I said.

Every time you disconnect the battery, you should do this.

**stayer** · 10-28-2011, 06:20 AM

Doesn't work for you stepper motor idling. Any screws touch don't, it doesn't affect idle. You need to wash the throttle body. Tell model of the engine.

**Galanttuner10** · 10-28-2011, 07:09 AM

Originally Posted by stayer

Doesn't work for you stepper motor idling. Any screws touch don't, it doesn't affect idle. You need to wash the throttle body. Tell model of the engine.

On our throttle bodies there is an idle adjustment screw you can use to raise or lower the idle. That car is fine now so there is no need to mess with anything at this point

**eksz** · 10-28-2011, 07:36 AM

Originally Posted by Galanttuner10

car is fine now so there is no need to mess with anything at this point

Wiser words were never spoken.

Took over three weeks for it to get back to normal but she is back and running rock solid. Amazing how annoying something like a little idle problem can make you rethink the wisdom of continuing to drive a car you've had for 18 years. Bought her new in 1993 and just went over 269K miles. Other cars have come and gone in that time but the 7g keeps hanging in there.