Major freakin idle problem

[e30fr3@k]

Okay so here's the rundown: Idle is fluctuating between 5 and 9 hundred RPM on startup only. Rev it a little, drive it a little, no problem. However, if you just let it sit and don't rev or move the car, the "check engine" light comes on. The light also comes on when I go down a hill in a low gear (compression braking). The problem started occuring when my muffler went to hell. That's all the leads I have. I do know that I ripped off my muffler. I replaced my AFM boot (elbow) and cleaned my idle control vavle and TB with intake cleaner. All of my computer leads are connected to where they should be. Nothing is lose and there are no vacuum leaks. When I ran a diagnostics computer on it, the computer says "emission control (lambada)." I have no idea what that means.


I also get this strange rattling noise when I let the clutch out in nuetral. It's quiet, but quite clearly coming from the transmission.

 

[jrt67ss350]

The computer code is saying you have a bad oxygen sensor. They used to call them lambda sensors. Replacing that would be a good place to start, especially since the computer is telling you it is bad. But, before you do that, make sure the electrical connections to the O2 sensor are still connected and clean.

The rattling noise in neutral is most likely your throwout bearing. Could also be worn bearings in the transmission itself.

 

[xLibelle]

the Getrag tranny (if you have an iS) is known to rattle once the fluids heat up.
Mine rattles and my throw-out is brand new.

 

[epj3]

the Getrag tranny (if you have an iS) is known to rattle once the fluids heat up.
Mine rattles and my throw-out is brand new.

Where did you ever hear that? This is the first I've heard about it in the past 2 years I've been reading about e30's.

My tranny itself makes absolutely no noise. If i turn on the car without pressing in the clutch (in neutral), there is pretty nice silence.... if i Pressin the clutch allowing the clutch plate to not spin and then back out, the TOB made noise.

I HIGHLY doubt its the tranny. Likely culprit is your throwout bearing. It should be okay for now, but it's eventaully going to get louder and louder until you can actually feel it rattling around in the pedal. Thats when you know its time to replace the clutch (As I'm about to do to my car in a few hours...woohoo!)

 

[jrt67ss350]

My "tranny" used to rattle when it was in neutral and idling. I was always concerned that a bearing was going to fail. However, when I had my clutch replaced, the rattling went away - and it's no wonder, considering what my throwout bearing looked like. It's most likely the throwout bearing being noisy.

By the way, he doesn't have an iS, xLibelle.

 

[e30fr3@k]

Well, sounds like it's the clutch then...How often are they supposed to be replaced on average? The sound is quite loud and I can hear it through the floor and feel it in the clutch pedal.

Regarding the o2 sensor though, why does the "check engine" light only come on when I'm not accelerating. It's consistent in compression braking and idling. But as soon as I start to move, the light goes out. I'm so puzzled, and I'm gonna hope that my mechanic can figure it out.

 

[Ben]

I have the same rattling you guys are talking about, and i just replaced my clutch and TO bearing, so it has to be in the tranny. Im not too worried about it. when it goes, it goes and ill put another one in.

 

[jrt67ss350]

The sound is quite loud and I can hear it through the floor and feel it in the clutch pedal.

Ahh, you left out a critical piece of information in your first post. If you feel it in the clutch pedal, then it's your clutch. Period.

My original clutch lasted about 260,000 miles.

 

[e30fr3@k]

Holy crap....I only have 213k on mine...I guess if it's time for it t go, it's time for it to go. Anyway, off to the mechanic's now. Thanks for the help.

 

[jrt67ss350]

Hey, to get over 200,000 miles out of a clutch is quite an accomplishment. The clutches in most cars out there don't last 100,000 miles.

 

[e30fr3@k]

so...hung...over..ow. anyway, my mechanic thinks i need a new idle control valve. i went to the parts store and they said it's unlikely that it's the idle control valve and rather the 02 sensor. is this hard to replace? i know it's expensive, but can i do it myself? ow my head........

 

[Ben]

they are easy to replace, ask epj3, he knows all about them.

 

[e30fr3@k]

alright thanks. also, sometime the idle problem fixes itself while i'm driving. ie., if i'm at a traffic light, sometimes it might be a steady 650 an sometimes it might be from 500 to 800, it really all depends and i can't tell what on. If it's not consistant, what do you guys think is more likely to be the problem? idle control valve or o2 sensor?

 

[e30fr3@k]

Update (Improving but still a problem)

Okay, so the rough idle subsided...Why? Don't ask me. I'm glad it did though. However, my car does one of two things upon startup.

1) Revs to 1700 RPMs and stays there until I engage the transmission. Whereupon, it will rise to near 1700 RPM when in neutral and slowly drop as the engine warms to running temperature.It never drops below 900 RPM.

2)Revs to 900 and sometimes is at 650 where it should be and sometimes stays at 900 when idling.

Known problems are as follows (might help you diagnose)
*No muffler (that's right..none)
*High Idle
*symptoms of worn clutch (although I really can't feel anything in the pedal anymore, just feels like it's not gripping the flywheel right away.
*Something rattling in the back (probably has nothing to do with anything but damn is it annoying..has something to do with speakers or is just near that area)

Recent work includes
*New AFM boot
*Cleaned AFM, TB and ICV using air intake cleaner
*Tightened Accelerator Cable (going to loosen this a bit to see if I can get the idle to drop to 650 or 700 or something around there.


That's all the info I have off the top of my head at the moment.

Bottom line is "Is the Idle control valve the source of my high idle or is it something else?"
What can I do to test to be sure (besides just replacing the parts)

Any input (so long as it's not negative is welcome and appreciated)

 

[bichmgnt]

You're ugly. Wait, you said no negative input. Sorry.

Check your wiring. I had a broken wire on my 325es that caused a similar problem. Bentley has about eight pages of idle and electrical troubleshooting procedures that should help determine where the problem is. You might also check for fuel supply issues like your cold start valve and such. BTW, your idle should be a little higher - spec is 700 +/- 50.

Good luck.

Steve

 

[baby6]

did you find problem?????

Okay so here's the rundown: Idle is fluctuating between 5 and 9 hundred RPM on startup only. Rev it a little, drive it a little, no problem. However, if you just let it sit and don't rev or move the car, the "check engine" light comes on. The light also comes on when I go down a hill in a low gear (compression braking). The problem started occuring when my muffler went to hell. That's all the leads I have. I do know that I ripped off my muffler. I replaced my AFM boot (elbow) and cleaned my idle control vavle and TB with intake cleaner. All of my computer leads are connected to where they should be. Nothing is lose and there are no vacuum leaks. When I ran a diagnostics computer on it, the computer says "emission control (lambada)." I have no idea what that means.


I also get this strange rattling noise when I let the clutch out in nuetral. It's quiet, but quite clearly coming from the transmission.

Hi I just want know if you find problem with rpm because my car doing exacly same thing.thank you

 

[scrood]

Okay so here's the rundown: Idle is fluctuating between 5 and 9 hundred RPM on startup only. Rev it a little, drive it a little, no problem. However, if you just let it sit and don't rev or move the car, the "check engine" light comes on. The light also comes on when I go down a hill in a low gear (compression braking). The problem started occuring when my muffler went to hell. That's all the leads I have. I do know that I ripped off my muffler. I replaced my AFM boot (elbow) and cleaned my idle control vavle and TB with intake cleaner. All of my computer leads are connected to where they should be. Nothing is lose and there are no vacuum leaks. When I ran a diagnostics computer on it, the computer says "emission control (lambada)." I have no idea what that means.


I also get this strange rattling noise when I let the clutch out in nuetral. It's quiet, but quite clearly coming from the transmission.

Idle speed actuator by the sounds of it

 

[scrood]

Okay so here's the rundown: Idle is fluctuating between 5 and 9 hundred RPM on startup only. Rev it a little, drive it a little, no problem. However, if you just let it sit and don't rev or move the car, the "check engine" light comes on. The light also comes on when I go down a hill in a low gear (compression braking). The problem started occuring when my muffler went to hell. That's all the leads I have. I do know that I ripped off my muffler. I replaced my AFM boot (elbow) and cleaned my idle control vavle and TB with intake cleaner. All of my computer leads are connected to where they should be. Nothing is lose and there are no vacuum leaks. When I ran a diagnostics computer on it, the computer says "emission control (lambada)." I have no idea what that means.


I also get this strange rattling noise when I let the clutch out in nuetral. It's quiet, but quite clearly coming from the transmission.

Idle speed actuator by the sounds of it
Getrag boxes always rattle, even our Super Tourer equiped with a getrag box rattled its guts out. with the E30's I think its just the imput shaft bearing...

 

[epj3]

E30's idle poorly when cold, simple as that. I have never in my life seen an M20 eqipped car that idles 100% when cold. Even if it idles perfectly, it'll still DRIVE like crap.

 

[JimHow]

Had the exact same idle problem on my '87 325i. Pulled the rubber boot off and sprayed the throttle housing & idle control valve with throttle body cleaner. The engine now idles perfectly at 750rpm. I'd try this potentially easy fix before anything else.