Stalling at idle when hot

[tag4m]

My Stag has developed a problem that I can't seem to solve and neither can my local garage.

The car starts and runs fine for about 40 mins. Then when I slow to a junction of traffic lights the engine starts to stutter and die and it's a struggle to keep it running. After a further five minutes this becomes impossible and the engine will die as I come to a stop at a junction. At that point it won't restart. If I wait thirty minutes it's fine again and the process repeats itself. Any help appreciated. I love my Stag but I'm a novice when it comes to car mechanics.

Martin

[JeffW]

Hi

Have you checked the float levels in the carbs? Sounds like heat soak is boiling the fuel in the bowls. Easy to check and adjust.

Jeff

[Goldstar]

If Jeff’s solution isn’t the answer then it’s not unknown for a dodgy coil to break down when hot. Maybe try a new/different coil

[tag4m]

Thank you. I did wonder about the coil but thought that would cause a problem at all speeds and not just when idling. Does that sound right?

[stag8manod]

Hi, It could also be the condenser, they are known to fail when hot.
Cheers Ian A

[flying farmer]

Worn needle valves in the carbs float chambers can have the same effect. At idle when little fuel is being used the float chambers over fill and the mixture gets progressively richer until the engine stalls.

This can be checked by pulling up the knob on the inertia switch under the bonnet as the engine starts to struggle. With the fuel pump stopped the idle speed should increase as the fuel in the float chambers is consumed. Eventually the engine will stop as the fuel is exhausted, resetting the inertia switch will then allow a rush of fuel into the carbs which can often dislodge any particles stuck in the valve and can cure the problem.
Costs nothing so worth a try

Neil

[JeffW]

Thank you. I did wonder about the coil but thought that would cause a problem at all speeds and not just when idling. Does that sound right?

As Paul says when hot coils can act very strangely, so it may be just at idle. Also check the coil has not slid down its bracket to rest on the engine as that will heat it up and cause these types of issues.

Jeff

[DZP]

Hi Martin,
Also check the exhaust, do you have black smoke when the engine is stuttering?
If so, then a piston assembly could be sticking open, causing a very rich mixture.
As the engine cools then the piston assembly drops and the car will run OK.
Unfortunately, I think you need to remove the air filter and carb elbows to view the piston assembly position, so it is tricky when you are out-and-about.
But... you can remove the damper and insert a thin screwdriver (or similar) down into the oil to the needle adjuster to check the height of the piston on each carb.
I hope that helps,
Den

[LAMBRETTLAD]

Coil is a quick and easy change ,sounds very coil like

[sujitroy]

Worn needle valves in the carbs float chambers can have the same effect. At idle when little fuel is being used the float chambers over fill and the mixture gets progressively richer until the engine stalls.

This can be checked by pulling up the knob on the inertia switch under the bonnet as the engine starts to struggle. With the fuel pump stopped the idle speed should increase as the fuel in the float chambers is consumed. Eventually the engine will stop as the fuel is exhausted, resetting the inertia switch will then allow a rush of fuel into the carbs which can often dislodge any particles stuck in the valve and can cure the problem.
Costs nothing so worth a try

Neil

i'm running into a somewhat similar problem and am reading this thread. If the needles are worn and letting fuel through, then I suppose you could start the car without choke. In may case, I always need choke. I have a new coil with Luminition.
Sujit

[Niss]

i'm running into a somewhat similar problem and am reading this thread. If the needles are worn and letting fuel through, then I suppose you could start the car without choke. In may case, I always need choke. I have a new coil with Luminition.
Sujit

The first breakdown I had in my Stag was the new coil which came with the lumenition failing within 3 months of it being fitted.

[tag4m]

Thanks everybody for your help with this. Although I had a new coil about six months ago, my garage thought we should start with that. Changed it for a new one and I’ve done two longish runs in the past week and the problem didn’t materialise (still stutters a tiny bit at idle in gear - it’s an automatic - but can live with that). So looks like the coil was indeed the culprit.

Thanks again for all the advice - much appreciated.

Martin

[MikeParker]

I had a similar thing once and it turned out to be the small plunger valves that vent the fumes from inside the float chambers. They are operated by small rockers that contact the main throttle shafts. These plungers can get stuck over time. So to check, open the throttles slightly and see if the plungers move. If they are stuck you can grab them with some pliers and pull them out. Keep freeing them and eventually they will pop out under their own spring power. Some WD40 might help.

[sujitroy]

Any update on this problem?
Sujit

[DJT]

Sticking air valve (piston) in one of the carbs.