New Guy to E32 - Picked up 1992 735IL - Some small issues - Looking for input

[ARZ540i]

Hello All
Wanted to drop by and introduce myself and the new car, Well new to me,

I am normally over in the E34 forum as we have A 94 540I but I Just picked up a 92 735IL with 192XXX. White over parchment. Overall for the age and miles exterior and interior are in very decent shape and for the most part with the exception of a rear window most of the electrics works and I will be troubleshooting the rest. Have a full book of records dating back from new and the original window sticker. Overall I am happy with it for the $1600 I paid but paying such a low amount comes with issues so here goes.

When I test drove it had a rough idle and vibration, Anything about 2000 RPM and it was smooth as butter but low RPM and idle is horrible. Figured motor mounts which are on order. Looking and feeling the old one on Pass side of engine bay they look original and the maintenance history does not show them done before. I changed the plugs too which seems to have improved cold cranking time to start up, Was taking 3 or so seconds before now its more like 1 second to fire. But engine idle still seems off. As I have never owned a M30B35 before I wasn’t sure exactly how it should sound. It doesn’t drop RPM’S at all during idle but it almost sounds like it does. Does the M30 tend to sound that way? Also I have noticed that when braking from any speed over 30 MPH that the cars idle seems to surge a little. I guess I am looking at pointers on this. My next stop was going to be the ICV boot and give that a cleaning but looking at it looks like its been replaced.

Rotor and Cap are about 50K old or 6 years. I presume Wires too.

I have to get the car emission here in AZ prior to getting it tagged. I want to try and get the idle and surged fixed before then, My fear is it might fail emissions if the air/fuel is off or even worse if the CAT is bad.

Apart from the above I drove it 40 miles to work, all highway this morning and was pleased. The engine is something I will have to get used too. The 540I does a solid 70 at 1900 RPM but the little 3.5 hauling this big boat hovers around 3000 RPM and is louder. I like it though, Was showing an average 24.8 MPG which was pretty decent I though, especially running 87 Octane.

Any input and advice appreciated

Thanks All
Lee

[E32FAN]

For the idle, you may want to pull off the ICV - it comes off easily - and turn the rotor by hand.

They get sticky and then they do not rotate freely.

In operation it is full closed and then full open, and the duty cycle varies to control the idle. You can feel the vibration of the ICV body.

Clean the rotor with carb cleaner, etc.

[ARZ540i]

Quick Question - Take it easy never done this before !!!!. I have attached a picture of the ICV. I take it i spray carb cleaner in both ends of the metal sections at the front and clean out any crap inside if any. link attached, Response #6 by BMW SLANGEN?

I found a great write up by shogun but unfortunatelt the pics are no longer available.

http://www.bimmerboard.com/forums/posts/516747

Thanks

[E32FAN]

He says a muppet can do it.

You won't hurt it. Just spray cleaner in and then prod at the rotor until it turns freely.

[ARZ540i]

Thanks E32FAN - I might be outa luck on this one. Just pulled the latest recipt from the file. Thats been replaced about 2 months ago.. Not good. I will pull it anyway just to make sure and give it a clean. I guess vacume lines next

Another question - Would lack of valve adjustment cause this issue too? I found two recipts for adjustment in the files. One back in 1997 @ 61k and the 2nd @ 2003 @ 141K. I dont show another since then and car is at 192K and 9 years later. Obvious signs would be ticking i presume but would it also effect idle?

[shogun]

picks are unofrtunately gone, I just copied the write up and the link to the pics. Not my own write up.
Anyway, easy to understand from the description.

Valve adjustment IS necessary, also check the Banjo bolts. Go to my website, there to other DIY links, private DIY sites>>>Gale, he has all what you need for that including pics and even sells the drilled banjo bolts with wires

[ARZ540i]

Well i passed emissions. HC was 0.33 CO 7.56 and NOX 1.39 so pretty decent. Also took the ICV off last night, Its new and wasnt very dirty so now its onto the next step for this idle issue. Also got my indy set to do the valve adjustment this week along with the Banjo bolts. Hopefully he doesnt find anything terrible while in there

[ARZ540i]

Well ICV removed and cleaned tonight along with the throttle body. Also unplugged the battery hoping it would reset the ECU on how much fuel/air the car has been used too. No Luck, Still idles like crap. I have created this video with the hopes somone had or has the same issue and can point me in the right direction. New Plugs installed too. [ame]http://youtu.be/adajdNMegPY[/ame]


What should i be hitting up next? Dizzy cap? Car seems to operate fine once moving. Even the surge issue has gone after the ICV cleaning and plugs but this start up idle is super annoying. Motor mounts being done this weekend. Im sure this will help too

Any ideas?

Thanks All

also not sure what difference this makes but idle drops low when OIL cap is removed with engine running which indicates to me there is good vacume

[E32FAN]

Perhaps you have breaks in the rubber hoses and housings, and these breaks are admitting variable amounts of unmetered air.

Try prodding the rubber parts while listening to idle speed.

[EEDegreeToDrive]

Perhaps you have breaks in the rubber hoses and housings, and these breaks are admitting variable amounts of unmetered air.

Try prodding the rubber parts while listening to idle speed.

--Sounds like the IAC motor, but reads like you ruled that out.
--The M30 runs happiest on 89 octane, throw a bottle of injector cleaner in it for good measure. It does OK on 87, but I usually reserve that for highway trips by myself. If I have a car load ,or am driving around town or through the hills I run 89. Anything higher is a waste and might cause carbon buildup
--Don't run anything but cheap copper plugs (Bosch or NGK), the ignition system likes it plain and simple. The Bosch Super Plus seem to work well for me, lasted 60K, looked great when I changed them with out w 6 more.
--Distributor cap and rotor are cheap at Pelican or Rock Auto
--Your throttle position sensor (or one of the micro switches) might have a dead spot, mine hesitates at like 5% throttle sometimes

Perform some/all suggestions, then take her out for a spirited drive for an hour, it'll be purring when you get it back home.

[E32FAN]

--

Perform some/all suggestions, then take her out for a spirited drive for an hour, it'll be purring when you get it back home.

Yes, BMWs need to run, and the more backroad variable-elevation curves, the better.

A mechanic once told me, "There's nothing wrong with this car that a good DRIVE wouldn't fix. "

[ARZ540i]

EED - Plugs i put in what was recondmended by Autozone was Bosch platinums. Not double prong but there not copper thats for sure. They wasnt to expensive either. What plus are you running? Model number if you have it.I would be willing to do them again to copper if thats what the car needs.
Motor mounts going on Tomorrow. I think i am going to take off the ICV/AIR BOX/ plastic and rubber hoses and the MAF, Throttle body and give them a good cleaning again. If i can source a Dizzy cap and rotor today i will be doing that too. Will report back.

Thanks Again