Poor idling

Hi there

I am currently restoring a 1984 MK1 GTi. I bought her from a chap who spent thousands on the engine and hugely modified it. Apparently it has BMW pistons fitted with a 2 litre billet crank, the head has been reworked and a prety fierce cam is fitted. As far as I understand the motor now displaces 2.1 liter. The car has been standing for most of the last 14 years during which time the engine work was done along with some suspension work, new gearbox and brake upgrade. I have been sorting out the bodywork, interior and wiring. The problem that I am facing at the moment is with the Idling. The car simply refuses to idle. It is quite lumpy because of the cam fitted (not sure of the duration) and it will idle very low with lots of engine shudder and then die. I have checked the aux air valve and even swopped it with my other GTi's one with no change. I cannot determine that there are any air leaks as the rpm doesnt change when I spray arround the system with carb cleaner. Adjusting the idling screw doesnt seem to make any difference to the idling :dontknow: I have tried to set the timing to the standard 6 degrees, a bit difficult as she wont realy idle, but I think it is prety close.

Is there perhaps anything else I should be looking at? I will be seeing to the co% once I have her back on the road as I dont have the equipment to do anything about it right now.

Any help will be greatly appreciated, thanks

take the big boot off the top of the air flap on the air box and make sure the plate is sat right , ie at the bottom of the cone and that there is a equal gap all the way round.

if that is fine then it sounds like it maybe running wrong.

what colour are the spark plugs? black = too rich so try leaning it off a smidge and see if that brings the revs up (it should idle around 950 rpm)

you wont know 100% untill its on co machine but a high lift cam will make it lumpier at idle.

it could be a few things though…. timing out (you need to set it at the correct rpm and with the vac unplugged) the fueling out due to a blocked injector, a leeky injector, the fueling just being set wrong…

Hi

Thanks for the reply. The cone of the airflowmeter is right as you described. All the injectors are brand new directly from bosch, so there shouldnt be a problem there.

The plugs are a very sooty black. I am not sure if that could be because the car hasnt been out on the road for some time as I am still busy assembling things. It has been started now and then to try and set up the motor. If I am to try and get her a little leaner which way must I turn the mixture screw?

As far as the idling is concerned I tried my best to get the idling at about 900 by opening the throttle slightly to encourage idling and the advance was removed. Will this affect the timing in any way?

I will try and get it to a shop later for correct co setting, but that may take a while as the vehicle first needs to be put back on the road.

back = rich,

iirc (im in Korea at the mo so cant double check my haynes notes) its left to lean and right to rich… but im only about 85% sure on that as its been about 6 months since I played with K jet

opening the throttle to raise the revs is a bad idea as it will increase the vac on the system, open up the idle valve and then lean the mix off with the long allen key, this will raise the revs up iirc, (again been a while if i had the car in front of me id be fine) the opening of the throttle wont effect the timing if the vac is removed but it will effect the fueling, so as a quick check of the idle timing it would be fine but once you have got the mix sorted then set the idle correct and set it again,

if its a really high lift long duration cam it might not idle well at 900 and may need to be raised to 1k to get a smoother idle..

where about in the country are you? if you anywhere near notts I have a home CO machine you can use and can lend a hand if you like.

I am actually in South Africa. Thanks though for offering! What you say makes sense. I will try and adjust the co's and see if it affects the idling. I wont keep the idling adjusted up manually, it was just to somehow try and get the motor running to adjust the timing which was also way out. The cam seems to be quite heavy, so I will propably end up setting the idle at 1000+. The car does run perfectly though except for the idling problem and the throttle responce is phenominal.

Thanks for the help, much appreciated!!