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Ross, Diagnostic and repair technician
Category: Car
Satisfied Customers: 1183
Experience:  Licensed diagnostic and repair technician
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My VW polo is misfiring at low revs and on idle. It is a 1999

Customer Question

My VW polo is misfiring at low revs and on idle. It is a 1999 1.4 CL 8v engine. Could this be an injector problem or associated with a HT lead other ignition system fault?
Submitted: 5 years ago.
Category: Car
Expert:  Ross replied 5 years ago.

techmachine :

Hi, welcome to Just answer! My name is Ross and i will help with your question

techmachine :

The next part to change would be the HT leads. I would recommend you change the leads and the distributor cap and rotor arm too as these often get forgotten about during services, I have had a few misfires in the past which were caused by the distributor cap and as all of these parts are service items, I would do these first.

I have had several Coolant temperature sensors cause this problem on these engines, There is a 4 pin plastic sensor that clips into the coolant flange on the right hand front of the engine, If you have access to a diagnostic scanner it may help identify this as a cause, but these fail regularly cost around £27

If the problem is still there I would advise you to fit some spark detectors that will show the spark while the engine is running, this will help identify whether its caused by lack of spark or an injection problem. If there are no problems with the ignition it could be related to a fuel injector. It would be wise at this point to carry out a compression test just to ensure all cylinders are of equal compression, If you smell un-burnt fuel in the exhaust its more likely to be a problem with ignition that an injection problem.

I hope this helps, please feel free to ask if you need further assistance, regards, Ross.