Hi all,

 

My 1986 Polo’s HZ engine is running badly. When cold, the engine cuts out whenever I need to stop. When warm, it feels like it wants to stall but the engine kind of catches itself and sounds lumpy. It feels low on power and the fuel consumption isn’t great. It makes driving it a bit scary and dangerous as I don’t want it cutting out on me at busy junctions etc. I’m really keen to fix this problem. I just want to learn how to diagnose and repair this issue.

 

I believe that these symptoms are caused by a vacuum leak somewhere. Could this be at the rubber carburettor flange, somewhere in the vacuum pipes or maybe from a blocked jet in the carburettor?

 

I have a genuine VW carb flange to replace the one on my car currently. However I’m unsure on the following:

 

I have a Pierburg 1B3. How do I clean the carburettor jets? Do I need to remove them and what products/cleaning process do I need to do to ensure I can clean them properly and without damaging them?

 

Please can someone tell me which vacuum pipes need checking too?

 

Thanks

Carb flange is always a favourite.

 

If you think it’s at fault try pushing down on the centre of the air cleaner housing and see if the engine note changes.If it does the flange is at fault.

Alternatively  try gently lifting the air cleaner inlet nozzle.Again, if the engine note changes then it’s the flange.

 

There are two jets/emulsion tubes on the 1B3 that can be removed in situ, these can be seen when you remove the air cleaner lid.The main jet and accelerator jets require the removal of the carb and the carb top cover removing, which can end up with damaging the gasket in the process.

 

For cleaning, get yourself a aerosol air tin to blast through any jets. Don’t poke pins or anything metallic in them as you’ll damage the calibrated orifices.

 

There are vac pipes from the air cleaner to the carb and carb to distributor vacuum housing. There is also vac pipes to the idle speed boost valve system. One goes from the inlet manifold to the solenoid on the bulkhead and then onto the Idle speed boost valve. These are made up of plastic pipes and rubber connections. 
 

However, in my experience poor running is usually caused by Mal- adjustment of the carb or more likely, the carb flange is split.

Edited 12 May, 20224 yr by mk2tastic

Thank you for your detailed reply. From what you’re saying and by my own curiosity, I believe that the carb flange is at fault. I did lift the plastic nozzle that is clipped to the side of the air filter box and the engine note did change and ran better for the brief second that I was messing about with it (been told that the nozzle is rather pointless and can be removed as it puts extra wear on the carb flange due to its awkward positioning). As I wiggled the nozzle free, I lifted it up and the engine note changed. So I’m pretty certain the flange is my issue.

 

Can the two jets on the top of the carb be removed by unscrewing them?

 

Lastly, do you happen to know the correct torque settings for the bolts of the carb flange and the correct torque settings for the carburettor bolts so that it can all be correctly seated again?

Edited 12 May, 20224 yr by AnonyMoose

Definitely sounds like a carb flange issue from what you report.

 

Yes, both jets can be unscrewed with a small flat bladed screwdriver.

 

I can’t find a torque setting for the carb bolts, but they are only 6mm, so it won’t be a lot(5-10Nm?)  they just need to be tightened evenly to prevent distortion of the rubber flange.

With regard to the air cleaner, do you mean the cone end or the whole fitting that slots in and clips onto the main round section?

 

The cone end can be removed but I don’t see the point in doing it(I’m a purist running the same standard carb set-up).I wouldn’t remove the other section that contains the warm air flap either. You should have the flexi warm air pipe fitted from it to the exhaust  manifold, the pipe helps to add some rigidity to the air cleaner. 
 

The warm air system is crucial in cold weather as it takes warm air to the carb to help prevent carb icing and poor cold running. The Pierburg 1B3 seems prone to icing, (well mine does anyway!), so I’d leave it fitted to help prevent such problems.  You’ll get away without the flexi pipe in summer, but I wouldn’t run without it in the other seasons.

Edited 13 May, 20224 yr by mk2tastic