1984 bmw e30 318i vacuum advance problem

[Greyyegg]

Hey guys recently bought this e30 and its had a surging idle problem, but only when the vacuum advance hose is connected to the distributor vacuum advance diaphram. If I disconnect the hose the car runs fine. would this problem lie in the vacuum advance solenoid or the distributor itself?

[msservices]

You need to check the timing to confirm that it is distributor related. I think that car would require a good ole fashioned timing light to do that. The other possibility, though, is the idle control gizmos are not working right and you happen to let the idle air in by causing a vacuum leak when you disconnect the hose.

[Greyyegg]

I confirmed that the timing is right with the timing light, but as far as the idle control you’re talking about the ICV? I think it’s just weird how it idles fine after timing it and as soon as I hook up the vacuum advance line it just starts surging again.

[Greyyegg]

Also should the vacuum advance solenoid be pulling any vacuum at idle? When I had the hose off before I did notice it had vacuum and I thought it was only supposed to pull vacuum from distributor diaphragm when throttle was opened

[msservices]

If it has a solenoid specifically for the vacuum advance on the distributor then I would be checking that and also what triggers that as well. Also are you sure the right vacuum port is the one activating the distributor advance/solenoid circuit? Vacuum ports can pull vacuum at different times depending on where they are in relation to the throttle body/idle ports

[msservices]

I looked this up in the Bentley manual, it says there is a vacuum solenoid and a vacuum solenoid relay. There is also a couple different types of ignition control units depended on the year/build date.

[Greyyegg]

Hmmm. Well either my hoses are mixed up on the intake manifold or the solenoid is stuck open I believe.
It shouldn’t be pulling vacuum and advancing timing at idle.
I’ll look at the relay as well. Thank you

[richardodn]

I went through my Bentley at one point and extracted a bunch of the tests into a spreadsheet. The vacuum advance tests are on Sheet1. https://docs.google.com/spreadsheets...it?usp=sharing
Look for the section on Distributor Vacuum Advance: L-Jet

[superj]

If you get really bored, a totally worthwhile mod on an m10 powered 318 is to get an intake from an older m10 powered car and put a weber 32/36 on in place of the fuel injection.

Nevermind, you are in dallas so you get smog checks, right?

Even though it easily passes smog, it wont have all the smog parts anymore so it won't pass a visual inspection.

[02rollin]

I went through my Bentley at one point and extracted a bunch of the tests into a spreadsheet. The vacuum advance tests are on Sheet1. https://docs.google.com/spreadsheets...it?usp=sharing
Look for the section on Distributor Vacuum Advance: L-Jet

Thank you Richard, great reference. I don't log in here often but had to thank you for putting this together. I will be saving this. The vacuum advance solenoid was also used on the euro 325ix with modified throttle (m20b25 motronic 1.0 073 ecu) plate as well as the 1991 M5 for intake resonance flap. I was testing a bad solenoid on an s38b36 and recognized the box looked the same as the one onthe m10 318i vacuum advance firewall and the firewall of my euro ix. Thank for posting this, there really is sparse information about the 1984 vacuum advance system.

[richardodn]

Glad it helped.