My MK7 1.6 TDCi Fiesta is suffering from rough idle (feels like a misfire).

EML came on yesterday and entered limp mode. Restarted car and EML went out, not in limp mode.

Currently hasn't re-occured. I managed to scan the car with a friends VCDS and showed the code: P042F - EGR System: Stuck Closed.

The rough idle can be felt in the cabin when stationary. Any suggestions on how to diagnose further?

Well I'd start with the code? Strip out and clean the EGR valve, make sure the seal isn't broken or something on it to make it stay closed. Quite common for EGR valves to cause IDLE issues, excessive fuel consumption or lack of power when pulling away.

Managed to scan for DTCs using Forscan.
Not sure where to start...

Quote

===PCM DTC P0806:00-28===
Code: P0806 - Clutch position sensor circuit range/performance

Status: 
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

===END PCM DTC P0806:00-28===

===PCM DTC P1412:00-2C===
Code: P1412 - EGR Valve Frozen

Status: 
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

===END PCM DTC P1412:00-2C===

===PCM DTC P0490:00-28===
Code: P0490 - EGR Control Circuit High

Status: 
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

===END PCM DTC P0490:00-28===

===PCM DTC P0336:00-28===
Code: P0336 - CKP Sensor A Circuit Range/Performance

Status: 
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

===END PCM DTC P0336:00-28===

===PCM DTC P1260:00-28===
Code: P1260 - Theft Detected, Vehicle Immobilized

Status: 
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

===END PCM DTC P1260:00-28===

===PCM DTC P2290:00-28===
Code: P2290 - Injector Control Pessure Too Low

Status: 
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

===END PCM DTC P2290:00-28===

===OBDII DTC None===
Successfull DTC reading, no error codes found

Module: On Board Diagnostic II

===END OBDII DTC None===

===ABS DTC None===
Successfull DTC reading, no error codes found

Module: Anti-Lock Brake / Traction Control Module

===END ABS DTC None===

===RCM DTC None===
Successfull DTC reading, no error codes found

Module: Restraint Control Module

===END RCM DTC None===

===PSCM DTC None===
Successfull DTC reading, no error codes found

Module: Power Steering Control Module

===END PSCM DTC None===

===IPC DTC U0401:68-28===
Code: U0401 - Invalid Data Received From ECM/PCM

Additional Fault Symptom:
 - Event Information

Status: 
 - DTC Maturing - Intermittent at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Instrument Panel Control Module

===END IPC DTC U0401:68-28===

===IPC DTC B10D7:51-6C===
Code: B10D7 - PATS Key

Additional Fault Symptom:
 - Not Programmed

Status: 
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC
 - Test not complete

Module: Instrument Panel Control Module

===END IPC DTC B10D7:51-6C===

 

Start with the EGR valve tbh...  

Crank sensor could also cause rough running as well.

Clear those codes and see which return, EGR almost definitely will.

Thanks, the car is on 72k miles and had the EGR valve replaced at approx 60k miles.

Cleared all codes, ran for a full week. Lumpy idle when started from cold and stationary at junctions etc.

No EML lights or codes logged. Issue persists...