[VjaceslavB]

Good time of the day folks,

Need your help please.

Issue appears to be only when outside is a warm weather. Below +3c starts fine, warms up fine no issues at all. But the warmer weather is the worst my start ups, once car hits at 700rpm on idle starting from cold there is a weird hoover noise starts to come up from underneath of a car from the drivers side and at this time i get rough idle for around 20-30 seconds.

No fault codes present. Checked injectors during that rough idle and all good as well as under normal conditions. Glow plugs controller has been replaced even tho there is no codes stored in the vehicle. Trying to find a solution for months now, already coded out and cleaned EGR and deflapped manifold with a good clean down too with no affect on my issue.DPF still in and seemed to be doing well with regens etc.

That sound and rough idle come along together and only when its warm outside. Please help totally lost of what needs to be done, i would suspect secondary air pump making that hoover noise, but im not sire and dont want to throw money on parts that are working fine... hence looking for your help please. Had mechanic looking at it with no success in diagnosing root cause.

Thank you.

[VjaceslavB]

Made some observation, when that happens... battery voltage through diagnostic sits at 12.2v,as soon as i insert key it drops down to 11.2v,upon starting vehicle it slowly climbs back up to 12.2 and goes up to 14.4v within like 20 seconds, so i would assume that battery is a culprit and causing for glow plugs not to fire up until it gets voltage resulting in a rough idle?

[335dlci]

Diesels dont have secondary air pumps. You may have a glow plug module issue.

[VjaceslavB]

Originally Posted by 335dlci

Diesels dont have secondary air pumps. You may have a glow plug module issue.

Thank you for your reply.No womder why i could not find one 😁 On my previous 325D when i had problems with glow plugs and controller ive had rough idle at all time on cold start no matter of rpm, and during hot weather it was fine. Here the rough idle from cold only feels and visible at 700rpm,and the warmer it is outside the worst it gets. But only on cold start and only at 700rpm

[leoberti]

Originally Posted by VjaceslavB

Thank you for your reply.No womder why i could not find one 😁 On my previous 325D when i had problems with glow plugs and controller ive had rough idle at all time on cold start no matter of rpm, and during hot weather it was fine. Here the rough idle from cold only feels and visible at 700rpm,and the warmer it is outside the worst it gets. But only on cold start and only at 700rpm

Have you managed to find a solution?

I also have a rough idle on my 520D N47 engine. But its not weather depended.
It doesn't matter if its cold , warm... only at idle, the car begins to shake, and the RPM needle fluctuates. Once i put the car in motion all the trembling is gone and everything runs nice and smooth.

I have cleaned the air intake , changed the engine brackets, checked the injectors.

I have no errors stored in the ECU. The glow sparks seem to work fine because when its cold i get a message in the dashboard ("preheating .." ) for about 2 seconds and then the car starts up.

But this rough idle is present even when the car is warmed up to 100 degrees.

What else should I do?