'91 Polo 86C 1.0 Rough idle on cold start

Chat about your MKIII (86C) inc GT/G40 Polo
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kevin.amorim
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'91 Polo 86C 1.0 Rough idle on cold start

Post by kevin.amorim » Mon Jan 08, 2018 3:04 am

Hey guys, I've got a '91 Polo 86C 1.0cc and when starting when the engine is cold it won't idle if I don't keep revving the engine. Also if I don't rev it up both the engine and the gearbox vibrate A LOT making a lot of noise. If I depress the clutch the vibration seems to soften.

When hot the engine runs smooth and nice.

Any idea of what could it be? Or what to check? I've already replaced the spark plugs and cables.

Thanks!

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alexperkins
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Re: '91 Polo 86C 1.0 Rough idle on cold start

Post by alexperkins » Mon Jan 08, 2018 11:44 am

Is yours a carb or injection?

If its carb, its likely the auto choke has failed

If its injection, your throttle body might need cleaning up.

When was the last time it had a fuel filter and air filter change? You might also want to change the coolant temperature sensor.

With regard to the vibration, you might need some new engine mounts. They dont last forever

kevin.amorim
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Re: '91 Polo 86C 1.0 Rough idle on cold start

Post by kevin.amorim » Mon Jan 08, 2018 2:16 pm

alexperkins wrote:
Mon Jan 08, 2018 11:44 am
Is yours a carb or injection?

If its carb, its likely the auto choke has failed

If its injection, your throttle body might need cleaning up.

When was the last time it had a fuel filter and air filter change? You might also want to change the coolant temperature sensor.

With regard to the vibration, you might need some new engine mounts. They dont last forever
It's carb. If the auto choke failed, do I have to replace the whole carb?

The air filter has less than 2000km, the fuel filter, I don't really know. The car reaches the correct working temp after some time running...so I don't know about the sensor.

I will check with a mechanic about the engine mounts.

Thanks!

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alexperkins
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Re: '91 Polo 86C 1.0 Rough idle on cold start

Post by alexperkins » Mon Jan 08, 2018 2:19 pm

The carbs can be fixed - normally needs a full overhaul

You can look to replace the pierberg with a weber carb which is more reliable

Easiest route though is just to replace the carb and be done with it.

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