Hello,

I've come across a problem that was minor at first which now happens at every junction. Idling seems hard and very low, almost at the point of cutting out. Moving from a standstill is hard, like the revs just die out and i have to keep trying to rev it back up. But driving it seems fine, no issues there. Must be something to do with fuelling because it seems to drink the petrol pretty quick.

Anyone came across this before?

Engine/Car?

Sounds like a fairly generic problem. Typical causes are air leaks and weak spark.

oh god. How could i forget to put that.

It's a 340 1984 1.4

The 1.4s have special air restrictor in the pipe or T-piece that joins onto the valve cover breather, this feeds a large pipe that goes into the bottom of the carb/manifold area. If too much air gets into that the car will not idle correctly, but it usually would rev ok.

A weak spark means the fuel drowns out the spark and the mixture doesn't burn fully, but it will usually tick over ok. It is characteristed by the engine stalling when you try to apply power. A weak spark is caused by insulation breakdown of the HT circuit, maybe a dirty coil or a lead that has been pinched around a cable clamp. To literally look for leakage, open the bonnet in the absolute pitch black, let your eyes get used to the dark and then look at the engine running, you will see any voltage leakage in the form of a blue corona.

You could also have a rich mixture caused by carb problems/adjustment etc. You need to try and set the mixture and idle properly, that will tell you something. If it won't set right there are carb/air leak problems.

Maybe you have more than one problem.

Thank you for the advice.

I've been busy lately so haven't had the time go jump on here. I did have a peak earlier today and noticed that the 5 screws on top of the carb was extremely loose. I need a day where i can take the carb off and strip it down. As for the the HT coils i'm going to check that when i'm next out late.

Well it used the idle perfect just now it's goes from low revs to high revs.

The loose air filter won't matter, the car should run fine without it. If you have an air leak after the carb the tickover will not be consistent.

If the carb top plate is loose it will make a difference though, which would be the 5 screws, the air filter is only 3. My 1.4 used to do it continually.

The problem has came back. But even worst. The only way for it to idle is to have the choke out. I've checked the carb bolts and there all tight.
It just doesn't want to idle at all. Running out of ideas :/

Generally speaking very poor running/idling that is improved/corrected by choke actuation indicates a very weak mixture.
This usually is caused by air leaks. It can also be caused by a failing/failed idle solenoid (the solenoid operates in the idle circuit and is bypassed when on choke).

1. Check basics - ensure idle mixture screw is present and "near enough correct" (fully in then 2 full turns out).
Ensure idle speed screw has not backed off.
2. Check carb is not loose on manifold.
3. Check all vacuum pipes for leaks - especially the brake servo hose where it connects to the manifold.
4. If the car is CVT check the 4way vac valve and clutch disengage servo hoses for leaks. Pinch off pipes to primary units to eliminate failed diaphragms.
5. With ignition on - pull wire off idle solenoid and then back - solenoid should click.
6. Remove carb top (you need to know what you are doing - there are clips and linkages to release) and check for any contamination in the float chamber.
7. If you had the B172k engine I would also suggest change the rotor arm and dizzy cap - it's worth a look on the B14 as well (failing cap and rotor gives a weak spark which then fails to ignite weaker (though correct) mixtures - using choke richens the mix enough for the engine to run).
8. Long shot - failing fuel pump giving low float level and weak running or fuel supply line partial blockage.

Recon a good chance it's either carb loose on manifold or a split in a vacuum pipe.

Good luck - Mac.

mac wrote:6. Remove carb top (you need to know what you are doing - there are clips and linkages to release) and check for any contamination in the float chamber.

Funny you should say that

Weber 32DIR de-silt 2 by macplaxton, on Flickr

Can't remember the exact plumbing of the fuel expansion tank at the rear, but that's a good way to loose fuel. There'd be a distinct pong of petrol though.

Thanks a lot for all the tips and advice, much appreciated!

Turns out the fuel cutoff wire wasn't attached good enough. I took it to work and a work mate fixed the problem with a "ghetto" fix. It idles perfect and goes so nicely.

I'm going to need a spare one just in case it goes again. Do they still make them by any chance?

On an 84 year model you should have a Weber 32 DIR Type 104-100 with a "small body" idle solenoid.

Try either:-

Webcon,
Dolphin Road,
Sunbury,
Middlesex,
TW16 7HE.

+44 (0) 1932 78710o
http://www.webcon.co.uk
sales@webcon.co.uk

Or

Southern Carburettors,
7 Priestley Way,
Crawley,
West Sussex,
RH10 9NT.

+44 (0) 1923 533843
http://www.southerncarbs.co.uk

Make sure they know you need the later, hexagon, "small body" idle solenoid (these screw in and are sealed/secured by a composite washer - the early, round,"large body" types are sealed by an 'O' ring and secured by a grub screw which is not present on the type 104-100 DIR that should be fitted to your car.

Mac.

Thanks a lot Mac!