135 cold start up rough idle

[frozen]

I have a 09 135, had the DPs changed close to two months ago.
Not long after that the car had a miss / rough idle when cold, it then progressed to sometime throwing a engine management light when driving and not revving up properly.

I took the car back to Stealth JHB, we changed the spark plugs, replaced one injector, fitted a new Rennzport C.

The car rides awesome when warmed up, however they advised that on cold start up it still has the rough idle.

Car does not have SW loaded and is running the stock file.

Any ideas on what we need to look at?

 

[akash]

Coil packs?

 

[MikeR]

:skit: so Im just thinking - have you considered that last mod you did might not have something to do with this.

 

[Gaviny]

Engine will hunt if the exhaust is not correctly sealed to DP
Maybe check this 1st

 

[FiRi@Rennzport]

From my experiences....the rough idle was my coil packs. Having the jb4 made it easy though. The rough idle was later accompanied by a miss fire and and an engine light. Read the codes with JB4 and pointed to cylinder 1. Swoped cylinder derivatives 1 and 3 coils around and the error jumped to cylinder 3. Replaced the coil and everything was good.

My advise is get the codes read and take it from there.

Sent from my SM-N920C using Tapatalk

 

[frozen]

Thanks guys, very valuable information.

@MikeR, these issues did surface after the fitment, however the items I replaced need to be done in any event

 

[frozen]

Does anyone know what the average pressure reading on the HPFP should be?

 

[Flo-rider]

Sounds more like coil pack 1 and 4. Recently replaced mine after experiencing same problem.

 

[Zound]

There could be another injector faulty, the N54 injectors are prone to leak when they fail and this will cause a rough idle. But as suggested, get codes read and find out which cylinder is misfiring and take it from there from an ignition and fuel diagnostic point view.

 

[frozen]

Thanks for the feedback guys, will be reading the codes and taking it from there