Stalling when low revs/neutral

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Simonpiemon
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Stalling when low revs/neutral

Post by Simonpiemon » Tue Apr 21, 2020 9:43 pm

So as title sudgests... When the car is idling or has low revs it cuts out and stalls. This happened for about 10 minutes then was okay? Only happened really when I was in neutral or at low speeds.

Also since the oil light comes on at low revs but I think this is just a dodgy sender.

It's fine now but just confused and concerned it will happen on my way to work.

Any help would be much appreciated.

Thanks

Simon



GT_II
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Re: Stalling when low revs/neutral

Post by GT_II » Wed Apr 22, 2020 1:39 am

What carb does your engine have Simon? Pierburg or Weber? Was the engine cold or warmed up when the stalling started?



Vic
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Re: Stalling when low revs/neutral

Post by Vic » Wed Apr 22, 2020 8:54 am

Check the dipstick tube is also not broken as the dipstick will drop giving a false reading. Don't ask how I know.



mark1gls
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Re: Stalling when low revs/neutral

Post by mark1gls » Wed Apr 22, 2020 10:00 am

Is your car fuel injection or carb and what is your "normal" idle speed?


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Simonpiemon
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Re: Stalling when low revs/neutral

Post by Simonpiemon » Wed Apr 22, 2020 10:14 am

GT_II wrote:
Wed Apr 22, 2020 1:39 am
What carb does your engine have Simon? Pierburg or Weber? Was the engine cold or warmed up when the stalling started?
So it's a Pierburg Carbourettor and I'd been driving for about 30 mins when it started..



Simonpiemon
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Re: Stalling when low revs/neutral

Post by Simonpiemon » Wed Apr 22, 2020 10:15 am

mark1gls wrote:
Wed Apr 22, 2020 10:00 am
Is your car fuel injection or carb and what is your "normal" idle speed?
Carbourettor and I'd say around 1000..



GT_II
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Re: Stalling when low revs/neutral

Post by GT_II » Wed Apr 22, 2020 12:40 pm

Two possible causes:

1. A fault with the idle cut-off valve. This is an electric valve that when energised opens the throttle a bit via the throttle plate actuator (3-point unit). It's function is to stop the engine stalling when the engine speed drops below 1200 rpm. It shuts off at higher engine speeds to allow the throttle to close completely when you take your foot off the accelerator which saves fuel and increases engine braking. It also shuts off when you switch off the ignition to stop the engine running on. It is possible the cut-off valve stopped working for a while due to an intermittent fault, such as bad wiring to the valve or bad earth wiring to the carb.

2. A blockage in the bypass fuel/air channel. If some fine debris has got past your fuel or air filter, it could have been sucked into the idle bypass fuel/air channel, reducing the flow of fuel/air mixture into the engine at idle for a while before working its way through.

If the engine kept shutting off completely when you had the fault, 1 is more likely. If it tended to cough and splutter for a while before cutting off, then 2 is more likely.



Simonpiemon
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Re: Stalling when low revs/neutral

Post by Simonpiemon » Wed Apr 22, 2020 2:33 pm

GT_II wrote:
Wed Apr 22, 2020 12:40 pm
Two possible causes:

1. A fault with the idle cut-off valve. This is an electric valve that when energised opens the throttle a bit via the throttle plate actuator (3-point unit). It's function is to stop the engine stalling when the engine speed drops below 1200 rpm. It shuts off at higher engine speeds to allow the throttle to close completely when you take your foot off the accelerator which saves fuel and increases engine braking. It also shuts off when you switch off the ignition to stop the engine running on. It is possible the cut-off valve stopped working for a while due to an intermittent fault, such as bad wiring to the valve or bad earth wiring to the carb.

2. A blockage in the bypass fuel/air channel. If some fine debris has got past your fuel or air filter, it could have been sucked into the idle bypass fuel/air channel, reducing the flow of fuel/air mixture into the engine at idle for a while before working its way through.

If the engine kept shutting off completely when you had the fault, 1 is more likely. If it tended to cough and splutter for a while before cutting off, then 2 is more likely.
Thanks that's really helped! 😊 Where can I find the idle cut off valve? I think it must of just been a one off as its been fine since.. I'll check all the cables when I'm home. The previous owner took out the air filter and I had one fitted not long after. This was back in December mind.

Thanks

Simon



GT_II
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Re: Stalling when low revs/neutral

Post by GT_II » Wed Apr 22, 2020 3:51 pm

It's in the most awkward place at the back of the carb, the rectangular metal box in the picture below. The wiring connector points to the left (viewed from the front of the car), roughly at the end of the red arrow. When the engine is idling, you should find battery voltage here. Also check you have a reliable earth connection between the carb and engine, which is needed to complete the circuit.
cut-off valve.jpg
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