Dizzy & Vacuum Thing - 1.9 Gti!

[nveeate 78]

Hi,

 

Just trying to sort out the emissions on my car. Connected to the vacuum device tucked under the dizzy is a hose....is this meant to connect to anything else? I cant spot anywhere on the inlet manifold whee it can go!

 

Cheers

[Slo 283 1 Cars]

Goes to the throttle body underneath if I remember right?

[farmer 327 1 Cars]

That's right Slo, quite hard to see but put your hand under there should feel something.

[Anthony 1,000]

Worth checking that the vacuum advance unit isn't broken while you're there, as most seem to be these days and it has a noticeable effect on fuel economy and responsiveness on part throttle.

 

Easiest way is to try sucking and blowing through the pipe - if you can't then it should work (suck hard enough and you'll hear the plate move inside the dizzy) whereas if you can suck/blow through with little resistance then it's knackered.

 

As has been said it connects to the underside of the throttle body.

[nveeate 78]

Thanks all. Sucking and blowing awaits...!

[nveeate 78]

Aha, now located - someone has blocked it!

[welshpug 1,626]

Thats funny if its from the dizzy

 

Or is that on the throttle body?

[nveeate 78]

Blocked at the vac advance end!

[Anthony 1,000]

Almost certainly done as the vacuum advance has failed I'd say, as it results in a small airleak in effect.

 

However, a failed vacuum advance won't be the cause of any MOT emissions related woes.

 

Typically, high CO is rich running (eg AFM, ECU temp sensor) and high HC is poor combustion (eg ignition, cam timing, low compression, incorrect fuelling)

[nveeate 78]

Hi Anthony, that’s what I thought re vac advance, but it has passed the suck test so not sure of the reasoning.

 

General fettling, checking, connector cleaning and fixing a small breather pipe split has got the CO down from 7.8% to 2.6%. Not entirely sure which did the trick! Slightly lumpy for a couple of seconds on first turn of key, but MOT pass is 3.6% I think so will do for now. I have a spare AFM, but we’re back on the original at the moment.

[welshpug 1,626]

that is still pretty rich tbh, they should run very well at 1.5%.

[nveeate 78]

Ok, cheers. Will do some more fettling, and might try new vac advance plus swapping over AFM. Main thing was to get it through the MOT before messing about with it again!

[farmer 327 1 Cars]

Can get them refurbished.

[Anthony 1,000]

As said, it should really be more like 1.0-1.5% CO - much richer than that and I tend to find that they're very susceptable to hunting and general idle related issues.

[nveeate 78]

As said, it should really be more like 1.0-1.5% CO - much richer than that and I tend to find that they're very susceptable to hunting and general idle related issues.

 

Sorry, I meant the reasoning for the pipe being blocked off at some stage, not your reasoning!

[nveeate 78]

p.s. Compression test results wet and dry were very good, and I have fitted a new coolant temp sensor. Will try the other AFM, once it's though its MOT.

Edited January 10, 2014 by nveeate

[nveeate 78]

Just to update this. It didnt seem to make much (if any) difference to how the car runs if the vac advance is connected or not, and given that it has been blocked off I'm guessing it's been identified as faulty in the past.

 

I tried a couple of Bosch suppliers for the vac advance p/n 1 237 123 091, but the price of this has now climbed to £59+VAT. Saw an old post on here when it was £20!

 

Anyway, question is this - Anthony said pretty much every 205 GTI will by now have a faulty vac advance unit (or words to that effect!). On this basis, what's the view on whether it's worth spending £70 to get a new unit?

 

Cheers

Edited February 25, 2014 by nveeate

[iPlod999 143 1 Cars]

I sent mine off for a refurb to these people.

 

http://www.h-h-ignitionsolutions.co.uk/index.htm

 

£20 and a quick turnaround.

[welshpug 1,626]

depends whether you want it to run as intended or you don't care about it being a little bit inefficient and use more fuel.

[Anthony 1,000]

From back to back tests I've done, a working vacuum advance was worth about 4mpg improvement on my car in day to day use where you're predominently on part-throttle cruise. That's certainly a noticeable improvement in terms of miles to a tank - something in the region of an additional 30 miles to a tank.

 

I can't be bothered to do the maths, but I suspect if you're doing a reasonable number of miles then it won't take too long to recoup the £20-25 odd it costs for a refurb one from H&H in fuel savings alone.

 

That said though, if yours passes the suck test then it's quite likely working - connect it up and try it

[welshpug 1,626]

crumbs, didn't realise it was quite that much, well worth setting up properly then

[Anthony 1,000]

It will depend on usage of course and I suspect mine probably is in the upper range of what you'd get.

 

Gains on a track car where it's largely at full throttle or nothing would be minimal for example.

[nveeate 78]

Ok, cheers both of you.

 

Anthony...I tried the suck test but wasn't sure if it was conclusive! I must admit I sort of assumed that the fact the tube was blocked off suggested that someone else had decided it was faulty - only one owner really, and I don't think he would have known to do it, so must have been a garage.

 

Will try the suck test again, and depending on outcome try a refurb. I'm not too fussed about 4 mpg (as I do sod all miles and spread these across three cars!), but also wondered if it would make it run a bit better with new vac advance and then set ignition timing...e.g. on cold tickover?

[nveeate 78]

p.s. Mine is quite low mileage, but I'm guessing most dizzys are getting a bit worn nowadays....I wonder if a dizzy refurb from the same people would be worthwhile?