Hesitation on light throttle

Post by **pionte** » 17 May 2010, 20:20

I took Bertie for the first proper run of the year yesterday, and I am getting a slight Hesitation/ miss under light throttle conditions, it seems to clear if I floor the pedal , I know its not electrical as I have recently changed leads,plugs.cap and rotor to try and sort the problem but it has got much worse.

I took the carb off tonight and have cleaned out the jets and had a good look over it and all seems to be pretty good, the excel orator pump is working and spraying in fuel and all jets looked clear.

I have just read in wikki that an gas leak in the exhaust would cause this, and mine does pop back like a goodun on the over run so I think the exhaust is leaking a bit, my question is am I looking in the wrong place by looking at the carb and should I be looking more at the exhaust??

Thanks in advance .

Martin.

p.s its a 1.9 DG with Pierburg 2 carb.

Post by **kevtherev** » 17 May 2010, 20:29

you also may have an air leak.
vacuum pipes and gaskets are your culprits

Post by **dugwiththevwbug** » 17 May 2010, 21:33

if you have not run her for a while the paper gasket in the carb dries out and can let air through should swell up again once being used .
t25's like constant use it helps them really it does

Post by **pionte** » 17 May 2010, 22:13

dugwiththevwbug wrote:if you have not run her for a while the paper gasket in the carb dries out and can let air through should swell up again once being used .
t25's like constant use it helps them really it does

Whilst its apart would you recommend a smear of gasket sealant to help the seal?

Post by **jason k** » 18 May 2010, 06:27

at light throttle you have the highest vaccume in the inlets so any minor air leak will show itself.

new gaskets are pence.

Post by **dugwiththevwbug** » 18 May 2010, 07:54

I dont like gasket sealant on a carb as is can squeeze into the places where you dont want it. Just clean up any mating faces and use genuine gaskets and all will be good also trim the ends of any vacumn pipes as the ends perish and let air by.

Post by **pionte** » 18 May 2010, 08:20

Thanks for the help guys,

You may have hit the nail on the head, thinking about it whilst sleeping .... there was a vacum pipe not attached to anything !

one went to the advance unit on the dizzy and the other went er... no where! That may the problem, I will have a look at where it should go, I will prob order new pipes and gaskets from Brickwerks.

Post by **pionte** » 18 May 2010, 16:57

jason k wrote:at light throttle you have the highest vaccume in the inlets so any minor air leak will show itself.

new gaskets are pence.

Jason do you know anywhere that sells just the main large gasket? I looked on Brickwerks and I can only see a complete set which costs £32

Website · Post by **CovKid** » 18 May 2010, 18:52

Buy some gasket paper and make one with a craft knife while you're watching the telly. Always used to make my own and still do if thats all thats wrong with it.

Post by **jason k** » 18 May 2010, 19:07

i used to get my gaskets from jim at stateside tuning, but i only ever fitted any on my ac wedge

Post by **rustytop** » 18 May 2010, 21:52

Martin, I believe that I have the same problem as you. I have replaced 2 of the vacuum pipes so far and this seems to have made some positive diference. The ones I have replaced are:
the vacuum pipe from the carb to the dizzy vacuum advance unit and
this one from Brickwerks although the fit wasn't as tight as the one I took off:

http://www.brickwerks.co.uk/index.php?p ... t&Itemid=6" onclick="window.open(this.href);return false;

Hesitation has definately reduced and I can now pull away from a junction without having to "clear its throat" by applying some pre- throttle. Allied to this it does seem to have some more power low down. However, it is not perfect. There is still a slight hesitation and going downhill thottle off, it does lightly "pop" as well. So, for me, it is back to the engine bay to complete the replacement of the vacuum pipes and take off the carb, clean and replace the gaskets.
As you probably experience, apart from this, the van goes like a rocket and will pull 75-80 if I want it to. It is just annoying for the throttle response not to be linear... (obviously I understand this is no ECU controlled engine so can't expect perfection)

One question for others to help me: When I suck and blow into the vacuum advance unit via the 3.5mm vacuum pipe, I can hear the diaphram inside operating. However, I can continue to suck and draw air through the system - so it's not "airtight". Should it be?

Thanks

Post by **kevtherev** » 19 May 2010, 06:34

Post by **humphry** » 19 May 2010, 09:24

i was looking for an answer to that question

that explains why its a bit underpower

oh joy more money :run

Post by **kevtherev** » 19 May 2010, 09:27

I think brickwerks sell them

Post by **ghost123uk** » 19 May 2010, 10:36

Watching this thread, because when I run on petrol mine too has a flat spot at light mid throttle (annoying because this is at around 50mph in 4th) - it doesn't do it on gas.

As I rarely run on petrol I have not bothered too much about it

I don't think it's air leaks on mine.

I was wondering how the second throttle barrel's butterfly is activated, is it by the "pull down unit" thingy ?
Could our problem it be summat to do with this I wonder ?

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