Volkswagen Polo III (1994 - 1999) - 1997 1.4 8v - Misfire and hesitation | Technical matters | Back Room Forum

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Thu 15 Nov 2007 16:41

1997 1.4 8v - Misfire and hesitation - akialmera

Hello, hope someone can help

I have a 97 polo 1.4 8v {added to header so that people can see beforehand} and it is causing me concerns. It starts fine when cold but sounds loud and uneven on idle just after starting. Once the car is warmed up it will not idle steadily but persistantly the rev counter drops to about 800 and then rises to 1200 for a second before settling back down to its idle of about 1000 rpm. It repeats this regularly about every 5 seconds or so.
The car also hesitates when pulling from low revs but has no problems higher up the rev range. It is more difficult to start when left for a few hours after being warmed up, and requires me to hold the starter motor on for a few seconds after the engine has first caught.

So far I have replaced the distributer cap and rotor arm (both worn) and oil, filter and air filter. I blasted the throttle body intake with carb cleaner which improved things for a bit, though this is still black inside (is this normal).
The coil seems okay (mutimeter tested), the spark plugs are beautiful (just like the picture of what they should look like in the haynes manual) and the ht leads are new (though of dubious quality and slightly high resistance readings about double what they should be) they were fitted when i bought the car.

Everyone i speak to suggests something different to replace and i cant afford all of them.

Please can someone point me on how to test what is really wrong with this car.

Many Thanks

Edited by Dynamic Dave on 15/11/2007 at 16:49

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Thu 15 Nov 2007 18:12

1997 1.4 8v - Misfire and hesitation - Screwloose

First clean both sides of the throttle plate and the surrounding area to spotless with a toothbrush.

Then check for blocked breathers and air leaks [particularly where the manifold meets the head] and then have the throttle basic setting done at a garage with the right equipment.

Could the cold idle loudness be an exhaust leak?

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Mon 19 Nov 2007 10:15

1997 1.4 8v - Misfire and hesitation - akialmera

Thanks for the advice,

I gave the throttle plate a good clean with toothbrush, cloths and cleaner spray. The breather hoses look fine, and couldnt see any air leeks (WD40 around the mating joints). The car does run much better, still hesitates a little at low revs, especially in last nights rain. The engine is deinitely searching for idle now. It runs up to about 2000 rpm before falling gently down to about 1200, which is higher than the 1000 rpm it used to idle at. It basically does this every time you take it out of gear, very annoying in city centre traffic.

Sorry for my poor initial description, the loudness on starting was the car reving in pulses (like a kid saying brum brum brum) for a minute before settling down to its idle.

As for having the throttle basics settings done at a garage with the right equipment, how does one find such a garage and what is the right equipmen? I am based near Newbury and while our local dealer seem nice and friendly it does look phenominally expensive for a cheap little old car. Is there a website that lists garages with these equipments?

Thanks again.

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Mon 19 Nov 2007 10:39

1997 1.4 8v - Misfire and hesitation - Screwloose

Ask around; there's plenty of small places with suitable gear.

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Tue 27 Nov 2007 17:28

1997 1.4 8v - Misfire and hesitation - akialmera

Throttle basics reset at local garage, however this has made no difference. They tell me now that it needs a new throttle body, which are rather expensive.
The car now just idles fast, 1200 rpm and rises in revs by about 500 rpm and is slow to loose revs when taken out of gear.

Also, the car actually looses engine speed when you turn on the headlights, rear windscreen demister and electric windows. I thought normally the car compensated for the extra draw on the battery these ancillaries caused by increasing the idle speed. Is that right?

Thanks

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Tue 27 Nov 2007 17:53

1997 1.4 8v - Misfire and hesitation - Screwloose

Cleaning and resetting was worth a try; but it's clearly not worked if the revs are doing as you say.

I'm not that surprised if it needs a new throttle body - and yes, VW parts are not inexpensive; what have they quoted £400+? If they're right; it will only continue to get worse.

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