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idle drifts down
4 of 50 - June 7th, 2004 at 06:45 PM

Will anynoe help with the cause of the following?

After a few gentle dabs at the accelerator I leave the throttle completely off. The engine idles OK for about 3 seconds and then the rpm drops. This is OK when the engine is hot but not so good when it is cold.

Thanks


'77 2L bus with twin solex carbs. Recently changed main jet from 130 to 145 and air jet from 175 to 155.

Peter Leonard - June 7th, 2004 at 06:54 PM

because it's cold....:alien

Bizarre - June 7th, 2004 at 07:09 PM

Why did you change the jets????

4 of 50 - June 8th, 2004 at 03:37 PM

Thanks Peter but the same thing happens when she is hot, only when hot she wont stall.

Why did I change the jets?

I wanted to do a carby overhaul because there was a lot of black smoke and poor fuel economy

Once in side i found that someone had been using the left carby as a hash pipe. The air correction jet was virtually closed over

I was advised by a good mechanic to change the jets to a calibre more suited to an older engine

The bus runs like a dream now and has much improved fuel economy but this idle thing is a bit wierd

[Edited on 8-6-2004 by 4 of 50]

Bizarre - June 8th, 2004 at 04:14 PM

Quote:
Originally posted by 4 of 50
Recently changed main jet from 130 to 145 and air jet from 175 to 155.


sorry but still a bit confused.

"Why did I change the jets?

I wanted to do a carby overhaul because there was a lot of black smoke and poor fuel economy "

It was running rich and you have richened the system up by increaseing your jetting.

Ok ok - its running better?? just confused that you have said it was running rich and its now richer????

kombikim - June 8th, 2004 at 04:27 PM

the jet choice you have made is very good, this has nothing however to do with idle, it really only affects over about 1800 revs or so, if you have a '77 , then you may have a "dashpot" on the throttle cross shaft, (it looks a bit like the vacuum advance, without a tube off it) it is designed to delay the throttle going back to low idle for a few seconds.
the other thing is that the idle mixture could be a bit rich so that the plugs gradually load up with unburnt fuel residue, becuase they can't burn it all off, this reduces the idle speed through lack of efficiency when hot & can Vrtually flood the plugs when cold, causing engine to stall