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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22002
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Having starting problems with my vw polo 1.2 2004, it is only

Resolved Question:

Having starting problems with my vw polo 1.2 2004, it is only cold starting that is the problem and only intermittantly. the car starts easily most of the time, but if left overnight it can take 5 or 6 turns of the key to start it , then it can go for a couple of weeks with no problems. my local garage ha changed the water temp sensor with no effect . What do I try now?
Colin
Submitted: 3 years ago.
Category: Car
Expert:  Matt replied 3 years ago.
Hello Colin

if you haven't already then replace the spark plugs if any of them fail this checklist:

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp


Also check for exhaust leaks before the o2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.

this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst

The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers

Customer: replied 3 years ago.

Have just returned from a long weekend so have just got your answer, the car for all its age has only done 50k and is in good order. It was serviced and mot in dec and which point the plugs were changed and the exhaust checked. The problem has been going on for over a year gradually getting worse that is the time between the episodes is getting less, this question was prompted by a morning last week when I thought it wasnt going to start, the battery is new . once started in the morning the car runs fine all day


hope this gives you a fuller picture


Colin

Expert:  Matt replied 3 years ago.
Hello Colin

thanks for the extra infomation

This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being improved as things warm up on one of the major sensors so check the connection plug and wiring to the following;

Airflow meter

Crank position sensor

Cam position sensor

O2 sensor

Throttle position sensor

Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40

and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump

And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.

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