hes......itation (83 s3 na)

[darkcat]

SO! just passed MOT fiorst time no advisories!!! WOO!!!!

anyhoo... went and got a lovely fresh tax disk (becuase it makes the car run so much smoother.....!)

and some fresh shell v-power.

get up to temperature, drive around slowly a bit and notice a bit of a hesitation if i start off at low revs, so i tried it a bit faster, like your taking off from traffic lights in normal city traffic.

It bogged right down, like it was either severely under or over fueling, then ater 1-2 seconds it would catch up and carry on happily....

where to start??!!

i dont know if its relevent, but there is a small amount of back-firing through the carbs when cold, but i assume this is normal?

[jonwat]

Sounds like the cab pump system isn't working properly or maybe the mounting O rings are perished so I'd start with a rebuild of the carbs & replacement of all O rings together with everything else that looks knackered. Rebuild kits available from http://www.sjsportsc...ndex.php?mod=10

While you've got the carbs off it's a good chance to replace the distributor cap, rotor arm, high tension leads & give everything a good clean. It'll make starting a lot easier & she'll run a lot sweeter

[molemot]

I'd start by looking at the accelerator pumps...if you have the carbs off the car, and open the throttles, there should be four great squirts of petrol shooting out of the chokes towards the engine! Not quite as much as a firehose, but getting on that way. That's why sitting at traffic lights revving the engine as a bad idea...both from the point of view of economy and washing the oil off the cylinder walls! The other thing is a build up of varnish in the jets/slow running system, as that deals with the progression too...all the way up to when the main jets chime in.

[darkcat]

Thanks

Well, i did a full carb rebuild, however im not sure about how i should be setting the pumps up exactly, they are obviously tweekable....

That didnt solve the issue anyway!

It occurred to me that it was more likely to be spark based than fuel, as all cylinders where complaining.

i had a play with the timing, and its made it MUCH better, if not fixed it entirely...

has anyone got a tuning guide??

[skiing]

Mine always had a hesitation off idle as you describe - it was improved with a carb rebuild and proper tune up - however it wasnt until I had it properly rolling roaded and the jets swapped around etc. that it went. It is now brilliant and has no hesitation at all - I can put my foot down a roundabout and not look a fool as I splutter into the middle of the on-coming traffic... I had mine done at a place called Vulcan engineering down near Brands Hatch, it cost 140 quid and the Morland Jones lotus people lent me their box of carb jets - the car also runs more economically and they got some good power gains out of it - please note that the car is an HC engine now and stainless exhaust so it would be more power than a standard S3.

[darkcat]

FIXED!

well almost..

Turned out to be float levels! - i find it hard to believe that 2mm of float variation can cause such problems! especially given all the sloshing about on cornering etc....!!

feels MUCH better now set to 15mm from the top-cover-face.

[rogerch]

"Well almost" Does the choke influence any of this ? I'd still be checking for air leaks in the induction, and like John says, leads and cap.

[darkcat]

There is only a slight hesitation on fast take-off now.

cap, coil, plugs, leads, rotor all new, checked advance weights all moving ok. 99.9% sure there is no induction leakage, as im sure you know, on an NA, there is nearly no induction system anyway!

the fact that its now nearly-spot-on would still suggest an amount of fuelling tweekage to do.

getting there!

Edited October 2, 2011 by darkcat