Vacuum advance unit needs replacing

[Sireatalot]

Hi Guys..

Driving home tonight, 350i stalled a couple of times when stopping at lights and the revs were returning to idle. My matey suggested it could be the vacuum advance unit and that the diaphragm within the part could have perished..

Anyway, we got back to mine and he pulled off the pipe from the phelum to the thingy, checked for a vacuum and there wasnt one..

Does anyone know which one is the right one to buy..
found this link but not sure if correct one
http://www.simonbbc.com/ignition-spares/lucas-35d-...

Is there anything else worth checking whilst this part is being replaced ??

Thanks
Dom

[Sireatalot]

Hi Tony.

I'm car sharing at the mo with a matey who is a mechanic at the garage next to office.. He said it would be the first thing to check regarding the stalling at low revs.. To check the vacuum, he disconnected the pipe at the plenum end and sucked on it - in theory, replicating the vacuum from the plenum. he could not create a vacuum to the advance unit so really, his diagnoses was spot on..

with regards to checking the advance lever on the distributor - it looks like it is within the distributor housing so not sure how to see whether it's moving or not..

I'll have a look this coming weekend.

anyway, if the advance unit did need changing.. do you know if the part on the previous link is the correct one ?

Thanks.
Dom.

[Sireatalot]

mrzigazaga said:

What is your idle speed...ideally it should be 850-950rpm for a 3.5...Any lower then it will idle rough...Hunt and stall....

When cold, it will roughly idle approx 1000 but without feathering the throttle, revs will drop and stall. Once warmed up after couple of minutes it will idle at approx 1000 all day quite happy.

When warm, and after spirited driving, pull up to traffic lights and stop, again without throttle feathering, revs will drop below what should be idle and possibly stall - not everytime but it has happened more than once..

A couple of other symptoms.. not sure if related.. over the last couple of weeks, without any adjustment, there is noticeably more popping and bangs from the exhaust end and also at highish revs I have noticed a bit of pinking under heavy acceleration.


Edited to add... just a query.. if the Vacuum advance had gone, other than the low rpm idleing stability.. what would happen higher up the rev range ??

Edited by Sireatalot on Thursday 18th September 14:33

[Sireatalot]

Evening gents.

Thanks so much for the responses.. alot to investigate by the sounds of it..

in responses to you all.

Ian - It is only the tube from plenum to vac advance assy.. no one way valve is fitted.

Adam - no splits in tube, have checked that.. cant confirm the condition of diaphram untill its taken off and inspected.

Mark - normal unleaded is what i use unless there is massive queue, may go super.. Vacuum hose is not blocked, have checked. will try and check points condition etc this coming weekend.. yes i did have a couple of stalls at fest.. since then, I reckon 3 out of 10 drives it stalls if i dont catch in time with throttle.. having said that, other week when i attended the ACE - it didnt stall or want to stall once that whole trip.

Watch this space, will investigate as soon as pos.
Cheers
Dom

[Sireatalot]

keatsie said:

Be careful,it is possible that the vacuum advance has been removed and your distributor is modified to run only on mechanical advance. This is quite a comment modification and locks the advance curve, mine has been modified as such. so no matter how much sucking you do there will be no advance and is controlled entirely by mechanical advance.

Thanks for the warning.. how would it be confirmed whether this mod has been done or not ???

[Sireatalot]

Hi Guys..

Just a quick update..
The Vacuum advance unit has been changed today by the garage along with the distributor rotor arm.
I was asked to take it round the block to see if there was a difference and also to aid the timing adjustment.

WOW.. what a difference for the better, the engine seems a lot happier returning to idle.

Following the bible, the timing has been set to 8 BTDC ( with the engine timing marks) now, I understand these markings can be in-accurate but as it stands it is now idling happily approx 900 rpm.

The trip home tonight will help determine if the timing needs further changes - my matey is going to bring his timing strobe with him to do adjustments to suit..

Fingers crossed that's now one more thing off the to do list.. Just need a good hoon now.. Bring on Saturday.

Thanks to you all for your input on this.
Cheers
Dom