Rough Idle on Cold Start

[Vatoman]

About a month ago I did some maintenance replacing my CCV, All associated hoses, Air distribution piece, VCG, Vanos seals, Oil filter housing gasket. If I go to start my car after a couple days I get a rough idle for a few seconds, nothing crazy however. RPM hang just below 1k so no jumps there and it drops down to normal after the SAP kicks off. Power is all there so no loss. I can turn it on later and etc and no idle problem at all. Mainly it seems to happen after it sits for more then a day. No codes at all being thrown. Its annoying the crap out of me. I dont like it and indicates something is off. Any ideas I can check? MAF is clean btw, intake boot no holes nothing really indicative of a vac leak. She has just under 72k plugs changed lil over 10k ago. New air filter too.

[edjack]

If this began after the work, it is something you've done wrong. Go back and retrace your steps.

[Vatoman]

nothing wrong with work, its been checked three times now. It was there prior to the job, I associated it with the ccv or vanos. It only happens after more then a day of sitting. Perhaps a stuck ICV im thinking now.

[Xeniczone]

How do you mean rough idle? Is it noisy for a few seconds? Does the engine shake around?

Seems like you have replaced everything that causes problems with these cars. Have you checked the power steering reservoir? My power steering was causing some noise upon start up once. Turned out the reservoir was near empty.

[xisco44]

im having the same issues on my m54
vanos done
ccv valve done
plugs
oil done

im going to replace the fuel filter because the car always die on the first crank
then i crank it again it will run with the crappy idle and then is perfect after the next day on cold start.... i also had a shi dy dyno run

[Vatoman]

Its a very slight shake and really only lasts less then 5 seconds its not violent at all or even moderate. Ill check ps reservoir but im near certain its full, its got new o-rings too. Fuel filter is just over 10k miles too. Its more of an annoyance then anything, I just wish it didnt do it. I used my car yesterday, so I could return to it now and it wont do it. However it seems about two days worth of sitting it will.

[Poolman]

Check the vacuum hose back behind the intake on the drivers side of the car. You will need to remove the cabin air duct work to get back there and also a flashlight and small mirror to inspect the vacuum hoses and caps that are there. Is the seal on the DISA valve air tight where it hooks to the intake manifold? I have made a gasket to make sure its sealed there. Might want to give that a try. If you haven't as of yet I suggest that you replace those Vanos seals. The will really wake the car up--the problem your having would point more to the seals going bad than anything else--at least to me.
Good Luck

[champaign777]

same on my 2 cars
with all new staff
about 10-20 sec very slight shake on a COLD start up
its not a vacuum leak and not a DISA and not a Vanos Seals as i have all this and much more new

it doesn't bother me as this is the only issue i have but its interesting to know the root of problem

i think its or second air pump or injectors

[bimpie]

i have the same issue when I start the car after it sits overnight, it is quite annoying at times but since it only does that for about 5 to 10 sec, I haven't really bothered to figure out what it is. I'm thinking about changing ignition coils and sparks since i have 122k on my car and maybe that can help?!

[champaign777]

don't know about coils ( never replaced them ) but not a plug issue for sure ( have 2 new sets )

[JaimeZX]

Same thing on my '98 540. But it lasts 30-45 seconds. Long enough that I usually drive off and next time the engine goes back to idle it's smooth as silk.

I just got the car in May, along with MX records going back to 2006. The previous owners took the car to multiple dealers and other shops to try to get this fixed and apparently they were all stumped.

[Poolman]

If you haven't replaced the Vanos seals, then you will have this problem for the life of the car while you own it. The seals bring back the proper engine timing of the vehicle..
I haven't had this problem for over 3 years now. Even in -0 weather my cars fires as soon as I hit the key and runs strong from there--even after sitting for days.

[Vatoman]

If you haven't replaced the Vanos seals, then you will have this problem for the life of the car while you own it. The seals bring back the proper engine timing of the vehicle..
I haven't had this problem for over 3 years now. Even in -0 weather my cars fires as soon as I hit the key and runs strong from there--even after sitting for days.

Vanos was done as stated in my 1st post. Car has no problem firing right up, shes a champ there. It not a erratic idle where the car sputters and rpms are dropping out.

[champaign777]

New Vanos Seals reduced cold start Rough Idle significantly but not entirely
i think almost all E39 M54 have this issue

it was discussed in many threads but i never see someone come to the root of it

[JaimeZX]

Plus there's no VANOS on the '98 E39...

[Vatoman]

New Vanos Seals reduced cold start Rough Idle significantly but not entirely eliminated
i think almost all E39 M54 have this issue

mine never had it till over this winter, funny enough my ccv was clean as a whistle really. I dont think its really vanos related at all. I thought it was CCV to blame. Though all the work I did was just to get it done before a problem poped up. Its funny how after two days it will and after one it wont. Since im seeing so many say the same it could be attributed to a M54 design. Perhaps a different weight oil may fix this.

[champaign777]

i always try different oil
the same , its not oil related , it's probably something to do with M54 design

[Xeniczone]

I'm not sure what you are using now, but try 0w-30 or 0w-40. Since the oil will be thinner at cold start it will be able to lubricate the motor quicker and reduce the chance of start up noise.

Plus there's no VANOS on the '98 E39...

There is. The 1998 was the boarder year for the M52 and the M52TU. The M52 has 190HP and Single VANOS. While the M52TU has 193HP and Double VANOS.

[kaineb]

M54 3.0 here with the same exact issue. All of the above items have been replaced with new OEM. Shaky for 10 seconds on cold startup. Never was able to figure out. Only thing left is to get the injectors rebuilt and see if that is doing it.

[PhillH]

Same deal here, everything has been replaced and still get the issue once in a while. With mine the idle is fluctuating up and down, like the rpms drop to low and then the computer sees that and jumps it back up, only for about 30 seconds on a cold start. Once in awhile it will drop the idle low enough to stall. If I drive right away it pretty much stops by the time I let off the gas at the first stop. I have figured out that if I turn off the AC, it won't do it. So I'm suspecting it has something to do with the load on the motor at start-up. Anybody got any ideas?

[champaign777]

I'm not sure what you are using now, but try 0w-30 or 0w-40. Since the oil will be thinner at cold start it will be able to lubricate the motor quicker and reduce the chance of start up noise.

i use Mobile 0w-40 NOW , no difference on a cold start
i used BMW Castrol 5w-30 with the same result

Same deal here, everything has been replaced and still get the issue once in a while. With mine the idle is fluctuating up and down, like the rpms drop to low and then the computer sees that and jumps it back up, only for about 30 seconds on a cold start. Once in awhile it will drop the idle low enough to stall. If I drive right away it pretty much stops by the time I let off the gas at the first stop. I have figured out that if I turn off the AC, it won't do it. So I'm suspecting it has something to do with the load on the motor at start-up. Anybody got any ideas?

idle should be stable , this looks like a vacuum leak

injectors rebuild can be nice to see in this thread

[Vatoman]

ive stuck to 5w30 Fuchs. Id like to think at 70k using nothing but premium Shell 93 and very rarely adding some injector cleaner they would be clean. However anything is possible.

[PhillH]

No offense, but oil isn't going to make an otherwise healthy engine idle rough. It doesn't have anything to do with that.

[Xeniczone]

No offense, but oil isn't going to make an otherwise healthy engine idle rough. It doesn't have anything to do with that.

The idea is thicker "cold" oil; 5wXX, 10wXX, 15wXX, takes longer to pump to the top of the motor than thinner "cold" oil 0wXX.

At the same time thicker "hot" oil, XXw40 XXw50, sticks to the top of the heads better providing better lubrication at running temp compared to thinner "hot" oils, XXw20 XXw30.

The theory was while 10w30/10w40 is good when the engine is new, as the engine gets older the 3-10 seconds that there is no oil in the motor (because it hasn't pumped up there yet) will eventually cause excess wear on the motor.

There are other complications with this though. Supposedly the wider the gap is between the cold rating and the hot rating the faster the oil breaks down. Also the thicker the oil, while it does provide better lubrication, makes the engine work harder to pump it. This reduces fuel economy.

[xisco44]

mine does this + turn off after first start so i start it again it wont turn off but have the shaky idle for a few seconds
Usual suspect replaced

will do injector cleaner in a bottle , fuel filter replacement.