My 2002 vRS is suffering with a mild misfire/hesitation, whilst the fault appears to be present at all times it is more noticeable at low rpms when under load (i.e. 2k rpm driving uphill), when cruising at a constant speed the fault is not felt. Start-up and cold running is more lumpy/erratic than usual also. The EML is not lit and no fault codes are present.

Things I have tried so far: Coil packs replaced, spark plugs replaced, driving with MAF disconnected, throttle body cleaned.

The question is where to look next? Could a blocking fuel filter give these symptoms, although at high RPM’s the fault is no worse? What symptoms would a boost leak cause? Any suggestions gratefully received.

Which coil packs and spark plugs did you fit?

 

Have you checked the breather pipes?

Fault codes?

As well as the above check coolant temp sensor.

If your idle is bumpy that may suggest an air leak

Also check the wiring loom to the coil packs it can get brittle.

Tried both ngk's and bosch super 4's, coil packs are bosch but have tried a combination of old and new ones. Coolant temp sensor would usually show other symptoms and the one fitted is fairly new. No fault codes are present. I think an air/breather leak could be a good shout, where are the usual suspects? Oh and idle is steady when cold and hot.

Usual suspects for the breather pipes are the one at the top of the engine on the right hand side and the ones under the inlet manifold (which are a bit of a pain to get to). Have a search on it - there should be quite a few threads as it's a common problem.

 

I replaced the above mentioned breather pipes with ones from 'creationsmotorsport' on eBay when I got the car and touch wood they still seem to be holding up well 5 years & 80k miles later.