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George Constantine
New User
Username: theo

Post Number: 2
Registered: 6-2012
Posted on Sunday, 19 May, 2013 - 09:07 am:   Edit PostDelete PostView Post/Check IP

Hi all, a 1979 Corniche Mk II, A4 Solex carb. I get a very rough idling and bad hesitation when I step on the gas to pull away. It seems to be ok on high revs. I adjusted the carb and timing, all seems well? Can anyone advice
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bobuk
Unregistered guest
Posted From: 92.40.255.89
Posted on Saturday, 25 May, 2013 - 08:02 am:   Edit PostDelete PostView Post/Check IP

Check accelerator pump

engine off look down chokes

work throttle and a squirt of gas should be seen

no gas

punctured diaphram

block some where

non return valve fautly

There is no adjustment for overall mixture. This is preset by the size of the jets.

go to workshop manual and read before you diy.

I hope this last line does not sound disrespectful

(Message approved by david_gore)
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Nigel Johnson
Prolific User
Username: nigel_johnson

Post Number: 117
Registered: 12-2008
Posted on Saturday, 25 May, 2013 - 11:15 pm:   Edit PostDelete PostView Post/Check IP

Nice to see you commenting again bobuk.

Regards, Nigel.
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George Constantine
New User
Username: theo

Post Number: 3
Registered: 6-2012
Posted on Sunday, 26 May, 2013 - 06:16 am:   Edit PostDelete PostView Post/Check IP

Hi Bobuk,

Thanks for your reply. I have a good fuel jet from the pump. I checked the compression, all coming up to around 10. No A2 and A3 plugs are a little oily?. I did replace the stem sills 2,000 miles ago, I was thinking of changing the HT leads again but I'm getting an even spark though, when using a see through adaptor at the end of the HT lead?
I,m not certain if it's the Solex carb or ignition now

Any further help would be much appreciated

Many thanks

George
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George Constantine
New User
Username: theo

Post Number: 4
Registered: 6-2012
Posted on Sunday, 26 May, 2013 - 06:38 am:   Edit PostDelete PostView Post/Check IP

Hi Bobuk,

Sorry I forgot to mention in my previous message, when I do remove the HT leads on the A2 and A3 plugs which are oily, I do not notice any variation on the idle or at least, very little and the engine continues to idle rough regardless?

Cheers, George
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Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 1028
Registered: 6-2006
Posted on Sunday, 26 May, 2013 - 07:47 am:   Edit PostDelete PostView Post/Check IP

Hi George, check for air leaks as well.

Split hoses and gaskets etc. A2 & A3 leads aren't swapped over are they?

Cheers, Paul.
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George Constantine
New User
Username: theo

Post Number: 5
Registered: 6-2012
Posted on Sunday, 26 May, 2013 - 08:04 am:   Edit PostDelete PostView Post/Check IP

Hi Paul, nice to hear from you.

Checked for air leaks etc, and no the leads are not swapped over, I've checked for that.

Cheers, George
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bobuk
Unregistered guest
Posted From: 94.197.127.20
Posted on Monday, 27 May, 2013 - 06:21 am:   Edit PostDelete PostView Post/Check IP

Check vacuum to cruise control under washer bottle

the speedostat ( aweful name) has sponge springs which turn to dust and cause an air leak

connect rev counter to engine

at idle note rpm

disconnect each plug lead in turn noting the rev drop which should be the same for each cylinder

if a2 and a3 are down ie no or little rev drop then check dizzy cap for cross firing and tracking

Using sunlight check inside the cap for grey lines which is evidence of tracking

I had this on a vauxhall Viva once and after an hour of fiddling they chief mechanic ( who used to a sunbeam talbot racing mechanic in the 1930s)
Explain that losing two cylinders could be a dodgy cap he was right and I have never forgotten -- no substitute for years of the spanners

This would also explain the oily plugs they can't clean themselves if they don't fire

These engine are not spark sensitive like some of the modern stuff

so providing the leads are giving a spark and are not tatty then they are good to go


I am assuming that 10 on compression means 10 bar or 150 psi

(Message approved by david_gore)
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George Constantine
New User
Username: theo

Post Number: 6
Registered: 6-2012
Posted on Tuesday, 28 May, 2013 - 06:49 am:   Edit PostDelete PostView Post/Check IP

Hi bobuk and Paul,

Thank you both for your help.
I have checked all points you both mentioned. Something very odd came to light whilst checking everything. One of the three bolts securing the AC compressor triangular bracket to the inlet manifold became loose and dropped off. This has left a clean hole straight into the manifold which was sucking-in air. I simply re-tapped the hole and replaced the bolt. The misfiring/flat spot was solved and the engine idle greatly reduced. The car now drives wonderfully and smoothly. Unfortunately I still cannot get the engine to idle 100%? on idle but I suppose I can live with that for now.

I thank you both again for you assistance.

George
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bobuk
Unregistered guest
Posted From: 92.40.253.185
Posted on Sunday, 02 June, 2013 - 05:34 am:   Edit PostDelete PostView Post/Check IP

Engine running

spray WD40 around carb base and throttle spindles if the WD40 gets sucked in then you have leak.

spindles should have no lift

They may have rubber seals

(Message approved by david_gore)
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George Constantine
New User
Username: theo

Post Number: 9
Registered: 6-2012
Posted on Wednesday, 05 June, 2013 - 02:49 am:   Edit PostDelete PostView Post/Check IP

Hi bobuk,

Thanks for the WD40 trick, I actually did this a while ago but couldn't see any visible signs. I'm now putting it all down to carb' wear

Cheers again George
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Benoit Leus
Frequent User
Username: benoitleus

Post Number: 70
Registered: 6-2009
Posted on Wednesday, 05 June, 2013 - 04:57 pm:   Edit PostDelete PostView Post/Check IP

Hi George,

I had the same problems and in the end I solved it by rebuilding the carbs and then having them professionaly tuned.

Benoit
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George Constantine
New User
Username: theo

Post Number: 10
Registered: 6-2012
Posted on Thursday, 06 June, 2013 - 05:22 am:   Edit PostDelete PostView Post/Check IP

Hi Benoit,

Thanks for letting me know about your experience.

Well, I've tried everything else,and it seems that my next step would be tackling the carbs (time permitting)
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bobuk
Unregistered guest
Posted From: 94.197.127.235
Posted on Friday, 07 June, 2013 - 07:03 am:   Edit PostDelete PostView Post/Check IP

An important to remember about this carb and other fixed jet carbs is that there are only two ways to adjust the overall mixture and that is by raising the fuel level which will richen the mixture and vica versa

Or by changing the jets

Both these are factory set

Check the petrol level

Set rpm 700 max any more will cause bump when selecting gears

Setting idle to slow causes rough idle

The mixture adjust screw only works on idle when under power the amount of correction from this adjustment has hardly any effect.

So adjust this to get engine as smooth as possible cutting fuel back will not give better mpg in fact the opposite happens

(Message approved by david_gore)

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