Idle problems and gearbox "Chatter"

[LogIK]

I'm having a few little problems with my MK3 Polo (not to mention the bad oil leak coming from the crankshaft oil seal or the cam shaft oil seal or even cylinder head - but thats another story)

Since I bought my car a few months ago (third owner) it has always had a few problems idleing and the gearbox "chattering" (a kind of fast ticking sound) when idleing in neutral. If I depress the clutch, the noise goes away, so I know it is the gearbox. some days it will not chatter and other days it can be very loud and almost develop a dry grinding noise It also disappears if I bring the engine revs up slightly, rather than letting it idle on its own. Could this be a worn input bearing on the gearbox?

As for the idle of the engine, the problem is that it is quite uneven. It can sometimes feel like the car is shuddering. If I kick the accelerator, it will sometimes stop this and the engine will idle quite smoothly (just under 1000rpm.) When it idles unevenly, it drops to just over 800rpm (one mark below the 1000rpm mark) and this can also make the gearbox chatter louder aswell!

Can anyone suggest any soloutions to these problems I am experiencing, and also, does anyone else have any of these problems? If so, please share them with me.

Thanks in advance!

[hardhitter]

Yeah, it could be the input shaft of the gearbox, or even the clutch release bearing. Have you checked the gear oil level ? Doubt that would cure it, worth trying anyway.

How do you mean the idle is uneven, does it fluctuate ?

[LogIK]

I recently have had the gearbox stripped down because of another problem, and the oil level was topped to the correct amount when it was reassembled again.

When I say the idle is uneven, I mean it doesn't quite tick over very smooth. The car wobbles and shudders like when you are going too slow for the gear you are in. I think it may be idleing a little too slow, but the main problem really is how the idle speed changes if I kick the accelerator. Sometimes, when it is idleing, the engine revs will go up slightly on their own, then back down again. Throttle body needs cleaning out maybe? Engine idle speed needs adjusting? - I'm not too sure

Maybe someone can shed sum light here. Anyone else have these problems?

[DanW]

Damn you've got the same problem as me and afew others. I cleaned out the air filter and it helped it out a little.
Now I'm thinking the alternator because it's worse when I turn lights on and heaters on. It almost sounds like it's going to stall doesn't it?

Check your oil see if it's black as mine, I'm going to have to change it and the filter this saturday... Hopefully.

Let me know how u get on m8


Cheers Dan

[LogIK]

Well I'm glad to hear that I am not alone with this one.

I replaced the air filter when I got the car as part of the service I did on it, so I don't think that's the problem on mine. I don't think it is the alternator because, on any car, when you switch the lights on or have any other electrical device running, the engine revs tend to drop. Modern cars will now increase the engine revs slightly to compensate for this. But yes, my car does the same when the lights are on. I'm going to try cleaning out the throttle body and see if that helps, but that can wait until weekend.

My dad is a semi-professional mechanic and he said that the 'uneven' idle in these Volkswagens is caused be the firing order of the engine. Like for example, instead of 2,4,3,1 on most cars, it would be 2,3,1,4 (I think ) Not sure whether this would cause it, but I know that my brother used to have a MK3 polo a while back and his didn't idle perfectly. Its looking to be quite a common problem. It doesn't worry me, its just, like DanW said, it sounds like its gonna stall and when its really cold, sometimes it does!

I check my oil regularly (because of the oil leak.) I did the oil and filter about 3 and a half months ago, and it is still golden/brown coloured! No black

Anyone else experience the gearbox chatter I describe?

[DanW]

Oh to add to the problems, my car missfired the other day, went on the motorway four 1hour and half, car sat on drive four bout 3hrs, then when it came to go again, it started being very jumpy and not wanting to start at all...

[LogIK]

Probably only firing on three cylinders. Mine had a problem like that, so I replaced the dizzy cap and rotor arm, and it fires on all four everytime *touch wood* You could probably get away with just removing the HT leads and dizzy and spraying them with WD40, cleaning the contacts.

I just started my engine up then from cold, and it is idling nicely @ 1000 rpm, with only a bit of gearbox noise. Probably won't be like that in the morning though

Anyone else have any experiences with this? Thanks.

[david burton]

probably a worn lay-shaft bearing on your gearbox - if the clutch release bearing goes then it makes a bad noise when moving the clutch only.

i have a chatter from the box on cold mornings, which goes after a bit. same as you describe but not quite as bad. contaminated gearbox oil will not help the matter tho.

from what i've heard, the vw gearboxes often have weak lay-shaft bearings....

[hardhitter]

The syptoms of hesitating and stalling etc can be caused by a faulty blue temp sensor, it basically tells the ecu what the temperature of the engine is and adjusts fuelling etc to suit. If the readings given out are incorrect it causes running problems.

It's also worth checking all your earth points, give them a good clean up with a wire brush or similar to make sure.

[DanW]

Im sorry im not good with books lol.
Where bouts in this pic is the temp sensor and the gubbinz u wer talking about?

[amstrange1]

Blue temp sender is just below your circle in that diagram - it's underneath the dizzy. There's a black and a blue sender side by side - you'll see the wiring loom going to them.

[DanW]

Thandy. Just take out and clean jobby. Nething special required? apart from an ultra-bendy arm?

[amstrange1]

It's the earthing points you clean up, the blue temp sender needs to be replaced with a new part. They're not that expensive (under £20 last time I got one I think) so are worth a punt. You might lose a bit of coolant when you swap it, but if you're quick you won't make a mess!

[LogIK]

When I had my gearbox done, the layshaft bearings were replaced, coz the guy said this was a common fault in this model of Polo, and usually fail around the 90K mark. The chatter in my gearbox is intermitent, but is usually upset more by a rough idle.

Been out today in my car on a few short runs with absolutely no problems. Was idling nicely on its own and I couldn't hear the gearbox. I've got a sneaky suspition that I could worsen as it warms up, but i thought it was worse when it was cold. Can I assume that my temperature sensor is working properly if I get a nice fast idle on cold starts, which returns to normal after about a minute or so, and also the accelerator pedal moves down on its own on very cold mornings when I switch the ignition on?

Where are all my earthing points on the car? Is it worth cleaning the throttle body out, or is this more likely to be the temp sensor?

[concept-e]

Hi,

My mk3 does exactly the same too. Sounds like it is about to stall, and the engine sounds as if it isn't ticking over properly. I give it some gas and it goes away, only to return when my foot comes of the accelerator pedal. After 10 minutes or more driving, it idles fine. And like it was said below, it is worsened by the switching on of electrics, e.g. lights, fan, radio. Seems to only happen when the car is cold.

Steve