my xkr 07, has an erritic idle sometimes, never goes above 1000rpm, but jumps from 500 to 1000 any ideas, using good fuel and all new filters fitted, driving ok. What should it idle at.

 

Does it have an erratic idle when cold? My XKR has an erratic cold idle...

 

yes sometimes, drove it 15 miles this evening and when stopped it was a bit jumpy on the rpm needle. Driving no issues, just one morning i started it and it died, started second time ok

 

Same engine as STR I think. Mine idles 600-700 sort of range, very smoothly. Switch off a/c in case it's part of the cause. Beyond that, go looking for things affecting fuelling (air leak, dirty MAF, bad IAT/ECT/etc sensor, bad coil, bad plug, ...). OBD can diagnose most and OBD live data lets you literally watch the values.