random misfire/judder

[jay1601]

car has started to play up over the last 2 days

it will randomly judder. feels like a light misfire. when i come onto boost it will judder then after about 4/5 seconds it will be fine. no fault codes/EML

going to start with replacing the plugs (done about 12K on current plugs bosch super 4's)

engine: AGU

with it being xmas haven't got a massive amount of spare cash at the moment. so don't want to go replacing random bits for the sake of it.

been looking around online seems like the ignition amplifier seems like this comes up alot when searching for misfires on the 1.8T lump. would this be a good place to start after plugs ?

 

[jay1601]

stuck new plugs in made no difference.

tested the ignition amp using this guide
AudiWorld Tech Articles

got around 200 ohms on all 4. so doesn't look like its that.

coils ?

 

[Gops]

Coilpacks are the most common issue if a misfire on the engines. Coilpacks can be tempremental so advice is to change them.

 

[Oke Phill]

Coilpacks are the most common issue if a misfire on the engines. Coilpacks can be tempremental so advice is to change them.

+1 for sure!

 

[Vex182]

Agree with coilpacks, you did not use Super 4s again did you? NGK all the way! I melted a set of super 4s and Badger5 say they don't get on well with those plugs too.

 

[turnstyle]

With misfire issues start with coilpacks
if they are fine (tested by swapping them around to see if the misfire changes cylinder), then check spark plugs and the coil pack loom.
If its spark plugs they will be coaked up with black soot or have evidence of arcing between points. Dirty brown colour is fine and normal.
Loom is easy - if you have splits and can see exposed wire its either knackered or will be giving you more issues soon. You'll need to keep tracing back along the loom until the splits stop, and then solder a replacement loom in. Sounds scarey but its easy if you take your time.

If all above is fine check vacuum lines - youll hear a hissing noice while engine is running. Thats a vacuum leak.
Check boost pipes

If its none of them and vagcom isnt helping the you'll need to check your compression.
It going to be either be piston rings (blue smoke from exhaust?) or head gasket (white smoke from exhaust, mayo like substance on oil filler cap/dipstick, coolant level going down).

A compression test will help you here (search youtube) and a sniff test on expansion tank for head gasket (goto a garage)

Following that above should help you solve an misfire issue.