Engine problems again!

[Krupa]

2 weeks, that's how long my car ran fine for. Changed the thermostat housing and rear wheel bearing, yay, running nicely for the Polo Show. Now, it's screwing around again.

It drives fine for like 80-90% of the time. Then, without warning it begins to judder, like someone's dabbing the brakes lightly and it refuses to idle. This tends to last for about a minute, and can happen at any point during the journey, then it's fine again.

It seems to accelerate smoothly, but holding it at 30mph for a while you notice it's having problems. I've never noticed it happen on the motorway. Sometimes though when you lift your foot off the accelerator it kicks back but it will only do this once at a time.

I've run the car till it's warm and unplugged the blue temp. sensor to test the sensors. This produces the correct effect: when unplugged the revs rise, when plugged in they drop. So my sensors are fine I assume?

The exhaust fumes smell normal, and the exhaust isn't really sooty so I assume it's not overfuelling either. Also, it's returning a regular 35-36mpg so that suggests that anything fuel system related is ok?

Any ideas anyone?

[bstardchild]

2 weeks, that's how long my car ran fine for. Changed the thermostat housing and rear wheel bearing, yay, running nicely for the Polo Show. Now, it's screwing around again.

It drives fine for like 80-90% of the time. Then, without warning it begins to judder, like someone's dabbing the brakes lightly and it refuses to idle. This tends to last for about a minute, and can happen at any point during the journey, then it's fine again.

It seems to accelerate smoothly, but holding it at 30mph for a while you notice it's having problems. I've never noticed it happen on the motorway. Sometimes though when you lift your foot off the accelerator it kicks back but it will only do this once at a time.

I've run the car till it's warm and unplugged the blue temp. sensor to test the sensors. This produces the correct effect: when unplugged the revs rise, when plugged in they drop. So my sensors are fine I assume?

The exhaust fumes smell normal, and the exhaust isn't really sooty so I assume it's not overfuelling either. Also, it's returning a regular 35-36mpg so that suggests that anything fuel system related is ok?

Any ideas anyone?

Sounds to me like an ignition related issue - maybe a spark plug lead breaking down - had a similar symptom on my MKII where it would cough occasionally under load sometime a few times in succession and then it would be fine for ages - eventually spotted a small ammount of arcing on the HT leads and once they were replaced it ran sweet as a nut from then on.......

Once a lead starts breaking down it normally starts to get worse soon but strangely this didn't happen with my old MKII it seemed to stay the same for ages thats why the problem was so hard to track down

[Tahrey1043]

i'd agree with that... and also... cleaned your injectors and changed your air filter recently?
i found a dirty filter made an amazing difference to the engine's cruising ability etc...

[Krupa]

I had a quick look under the bonnet earlier at the leads. When the car had its thermostat housing changed the lead from the dizzy to the coil was removed for a bit so I pulled that off and put it back on. Since then I've driven about 20 miles with no problems but that doesn't necessarily mean it's fixed sadly.

Air filter's also a big possibility. It's done about 10,000 miles I'd have said and I've removed the air feed so it's more likely to be dirty. Plus while I had the K&N on it the airbox was just sat in the garage gathering dust.

It's due a service in October anyway, so maybe it's just in need of a little TLC especially as it's had running problems this year.

[Tahrey1043]

my previous one ended up fuxed after maybe 7000 miles, if that much. if youre up to 10000, definately look at it - its been a smoggy old year...