Rough idle on start up

[Camillus]

My Volvo 740, B230k, has a very rough idle on cold start up, engine spluttering and just ready to cut out. Choke flap is closed as is normal. Took out the new spark plugs and had to clean off the dry, black, sooty deposits on them. Engine runs normally, and choke flap open, with a nice even tick over after 2 or 3 minutes. I have been told it could be condensation in the fuel tank, but the car is parked in a warm garage which is part of the house. I did notice that the engine temperature gauge rises from cold to normal more quickly than it used to. Does anyone know if a faulty coolant temp. sender unit could cause this to happen on a carburettor fed engine. All connections under the manifold look fine. Car has new dizzy cap and rotor. Any help or advice would be greatly appreciated. Tommy.

[Laird Scooby]

Originally Posted by Camillus

My Volvo 740, B230k, has a very rough idle on cold start up, engine spluttering and just ready to cut out. Choke flap is closed as is normal. Took out the new spark plugs and had to clean off the dry, black, sooty deposits on them. Engine runs normally, and choke flap open, with a nice even tick over after 2 or 3 minutes. I have been told it could be condensation in the fuel tank, but the car is parked in a warm garage which is part of the house. I did notice that the engine temperature gauge rises from cold to normal more quickly than it used to. Does anyone know if a faulty coolant temp. sender unit could cause this to happen on a carburettor fed engine. All connections under the manifold look fine. Car has new dizzy cap and rotor. Any help or advice would be greatly appreciated. Tommy.

Get the fuel level down to about 1/4 tank then add the contents of this to the fuel tank :

https://www.toolstation.com/methylated-spirit/p99550

Add all of it, don't try and skimp as it won't work!

Also what is your choke technique? Normally it's full choke to start then push it in ~ halfway so it idles smoothly, it shouldn't be all the way out for more than a few seconds after starting.

Also check your plug gap (0.65mm), for any air leaks and so on.

[Camillus]

Hi Dave, No it has an automatic choke. I have never liked them. They always seem to be acting up, even on previous cars, not Volvo, that i've owned. Plug gap is 0.7mm. Cheers,
Tommy

[Laird Scooby]

Originally Posted by Camillus

Hi Dave, No it has an automatic choke. I have never liked them. They always seem to be acting up, even on previous cars, not Volvo, that i've owned. Plug gap is 0.7mm. Cheers,
Tommy

Where did the automatic choke come from?

I was asking about your choke technique?

[360beast]

Automatic choke... is it a pooberg carburettor? (misseplt on purpose) the pooberg on my mk2 golf had a wax stat auto chooe and it was junk. In the last few weeks of it being on the car full throttle would get me 300rpm which would just about keep it ticking over and I mean just! Then after a minute or so it would burst in to life and act like normal apart from a flat spot at about 1500rpm until at operating temperature. Swapped it for a Weber in the end

[Camillus]

Yes, It's the 2B5 Pierburg carburettor. Several people have told me they are a load of crap. I think the Weber, manual choke carb. would be the best if not the most expensive option here.

[Laird Scooby]

Originally Posted by Camillus

Yes, It's the 2B5 Pierburg carburettor. Several people have told me they are a load of crap. I think the Weber, manual choke carb. would be the best if not the most expensive option here.

A wise choice, the Weber. The Pierbug carb is barely even useful as a mantelpiece ornament once polished so has no purpose for man or beast.

[Ross Slaughter]

Originally Posted by Camillus

Yes, It's the 2B5 Pierburg carburettor. Several people have told me they are a load of crap. I think the Weber, manual choke carb. would be the best if not the most expensive option here.

I also am going through hell with this awful carb.

[360beast]

Originally Posted by Ross Slaughter

I also am going through hell with this awful carb.

Weber is the way forward then... or twin webers.