VW Polo vacuum advance/retard

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Tue 9 Mar 2004 17:07
VW Polo vacuum advance/retard - fezzie
Hi, i've got an '87 VW Polo coupe and recently had an engine tune up, apparently my vacuum advance/ retard unit on the distributor is not working but the mechanic said not to worry about it too much. Should i be worried? is it a straight forward job of just replacing the unit or do i need to get the timing done again once the new unit is fitted?
Thanks in advance
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Tue 9 Mar 2004 18:46
VW Polo vacuum advance/retard - Civic8
It will cause you problems if it isnt sorted.if it has gone you should be suffering poor acceleration/starting probs.distributer will need to be removed to have it done but is fairly simple but fiddly if distributer is alligned correctly before removal timing won`t be far out when replaced.but will need checking/adjusting.
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Wed 10 Mar 2004 09:24
VW Polo vacuum advance/retard - Adam Going (Tune-Up)
The vacuum advance is primarily an aid to fuel economy, in that on most engines it is supplied from a port at the base of the carb, and only operates when the throttle is part-open. In this case the only effect will be reduced mpg. It would not usually cause any starting problem, but a very sensitive driver might notice some difference on light-load response.

On some Polos, however, it is supplied from a port in the brake servo vacuum supply line, in which case it should have full vacuum advance at idle. Therefore a diaphragm failure will have more noticable effect, as it not only results in retarded ignition timing at idle, but the air leak back through the unit causes No.4 cylinder to run very weak. So, as well as poor mpg, stalling and uneven running at low speeds result.

Personally I don't find it too difficult to replace the vac unit with the diszzy in situ, but agreed it is a bit fiddly. Timing should definitely be checked / adjusted afterwards, and be careful as to whether the spec for timing is vacuum connected or disconnected. You can obtain the vac unit (usually less than £20 + VAT and post) from any Bosch agent by quoting the distributor number (nine digit code, beginning 0231... or 0237...). I use a compnay called SED at Guildford on 01483 538038. A VW dealer may tell you that it is only available as part of a complete new distributor !!

Regards, Adam
Whatever is rightly done, however humble, is noble.
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Wed 10 Mar 2004 09:54
VW Polo vacuum advance/retard - fezzie
Thanks, all advice very much appreciated.
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