BimmerFest BMW Forum banner

1 - 20 of 59 Posts

·
Registered
Joined
·
78 Posts
Discussion Starter · #1 ·
On an '08 E64 650i
Before lockdown in the UK my E64 was running just fine. I laid it up for nearly a year but have now put it back in to service and it has an issue.
When starting it, it runs fine for the initial minute or so of fast idle, then it drops to the normal idle level which should be 650rpm but it stumbles and drops to 400rpm ish before surging every second to 550rpm. It feels like its misfiring but there are no codes logged. This continues even when warmed up to operating temperature although not as bad.
When driving, the car is fine and just as healthy feeling as it always was. It's just the idle.

When re-commissioning the car I changed the oil, coolant, and filters. Filled it up with 98 RON.

My initial thought was battery so I replaced it and coded a new one in. No change.
Then I thought maybe vacuum so I changed the CCV diaphragms. No change.
Then I changed the CCV pipework at the front of the engine. No change.
Swapped out the IVM. No change.

Disconnecting the MAF causes it to go to fast idle and it runs fine.

My next thing to try is VANOS solenoids.

I've been reading that it could be worn intermediate levers but I fail to see how they could be fine when I laid the car up and then worn when I re-commission it.

Any thoughts on this. It's driving me mad.
 

·
Michael
Joined
·
2,354 Posts
If I have learned anything about these cars is that you have to run them even for short periods frequently, and secondly keep the battery in top condition with frequent trickle charge. There is a cold start circuit on these cars which affects idle as you say it runs fine when warmed up. I remember a few guys having this issue so a deeper search may help.
 

·
Registered
Joined
·
775 Posts
When the car is cold started, its running in "open loop". The oxygen sensors need to warm up, and once they do, the car goes closed loop. Then the computers read the o2 sensors to deliver the correct amount of fuel and it has a closed loop system - basically has feedback from the o2 sensors.

I would also suspect vac leak - if it is a small one, then when you add gas to increase rpms you may see it go away. Another thing to do is put a scanner on it and read your lambda's to make sure they are in line. if not, that will give you a clue that air fuel mixture is off and then you can proceed to figure out why. it sort of sounds like the computers are having trouble keeping the idle going, which could be an air/fuel issue.
 
  • Like
Reactions: ard

·
Super Moderator
Joined
·
8,886 Posts
Remove your Vanos solenoids & clean them, along with measuring the voltage on each electrical plug. One side to ground will be around 2.84 volts, the other side to ground will be around 12 volts. The key should be turned on to do this, but leave the engine off. Any problems related to the Vanos system will cause the car to act like this. Search the Vanos system, & you will get a better understanding of how it works. Make sure to change both o-rings on each solenoid while they are out.
 

·
Resident Curmudgeon
Joined
·
24,552 Posts
When the car is cold started, its running in "open loop". The oxygen sensors need to warm up, and once they do, the car goes closed loop. Then the computers read the o2 sensors to deliver the correct amount of fuel and it has a closed loop system - basically has feedback from the o2 sensors.

I would also suspect vac leak - if it is a small one, then when you add gas to increase rpms you may see it go away. Another thing to do is put a scanner on it and read your lambda's to make sure they are in line. if not, that will give you a clue that air fuel mixture is off and then you can proceed to figure out why. it sort of sounds like the computers are having trouble keeping the idle going, which could be an air/fuel issue.
Agree When the car is running in open loop, the DME is NOT using the MAFs...it uses a default map that is mildly RICH.

When it clicks to closed loop, it uses the MAF...if there is an air leak, the engine will be running leak (since air is getting sucked in)

When you unplug the MAF the DME says 'whoops, no maf- use the default map'...which is mildly rich AND NOW IS PERFECT FOR YOUR LEAN RUNNING CAR.

(and while the DME is supposed to adjust fuel trims around this, it wont do it during open loop/cold start. This system also has problems when you have a small air leak which is a large factor at idle, but then at 50% -WOT, the leak isnt impacting the AFR that much, hence the correctioon that the O2s and MAFs that is done isnt perfect. (ie a leak of "1" when the engine is at idle and is running '5' is 20%...at WOT, which is perhaps 100, then it is only 1/100. And this varies constantly as you are driving around town....)
 

·
Super Moderator
Joined
·
8,886 Posts
He will have a big lack in horsepower until he repairs the problem, the Vanos system is the problem.
 

·
Super Moderator
Joined
·
2,074 Posts
Agreed, this is sounding more like a Vanos issue but all the above posts are relevant to the issue. When you take the solenoids out check out the gauze as it's probably caked in debris, compressed air is good for cleaning out this but also take note of Herb's advice to replace the O-rings or you might wind up with oil pressure issues to compound your problems.
As for vacuum leaks, a smoke test will instantly show any of these up.
Do you know if the car has had an aftermarket air filter such as K&N etc, some of these are oiled which can make its way to the MAF, the MAF can be cleaned but use a dedicated MAF cleaner for this, CRC does a good one but there are several different ones out there, if you do clean it, be real gentle.
 

·
Registered
Joined
·
78 Posts
Discussion Starter · #8 ·
Thanks for the replies guys. I'm going to get INPA on it again at the weekend and see what the Adaptations say.
The air filter is a stock BMW item. I never use oiled filters.
I'll go ahead and replace the VANOS solenoids and seals anyway as they're only cheap and easy to do.
Will report back once I've done some more investigation.
 

·
Resident Curmudgeon
Joined
·
24,552 Posts
I like just a heavy forceful cleaning of the solenoids will actuating them.. You will often times HEAR them 'getting better' as they go from a dull noise to a crisper snap when energized.

I only replace them when failed.
 

·
Super Moderator
Joined
·
8,886 Posts
Thanks for the replies guys. I'm going to get INPA on it again at the weekend and see what the Adaptations say.
The air filter is a stock BMW item. I never use oiled filters.
I'll go ahead and replace the VANOS solenoids and seals anyway as they're only cheap and easy to do.
Will report back once I've done some more investigation.
Do not buy cheap aftermarket Vanos solenoids, as they want work for very long, or not at all. Piersburg make a solenoid that will work, as they make many parts for BMW. These solenoids will save you half the cost of the BMW solenoids.
 

·
Registered
Joined
·
78 Posts
Discussion Starter · #11 ·
Swapped the solenoids yesterday and took it for a drive today. It's better but still rough at idle. It's not stalling now though so at least that's progress.
 

·
Registered
Joined
·
775 Posts
what do you mean by swap? new ones? or clean the old ones? or swap sides?
 

·
Registered
Joined
·
775 Posts
I wonder if its possible your computer needs to catch up with the new solenoids and the new tune they present.
 

·
Registered
Joined
·
78 Posts
Discussion Starter · #15 ·
Well, it's been a few weeks and it's still misfiring at idle.
Interestingly, it doesn't when the AC is switched on and the idle is higher. Turn the AC off and it misfires.
Oh, I swapped the MAF for the one on my buddy's car and that made no difference.
 

·
Registered
Joined
·
775 Posts
Did you get a chance to get INPA on it? Sounds like you're gonna need to so you can get some science working in your favor.
 

·
Registered
Joined
·
78 Posts
Discussion Starter · #17 ·
I'm planning to soon but things have been such that I've not had any time to work on the car. Things should be quieter in a few weeks and I'll be able to really dig in to it.
 

·
Registered
Joined
·
775 Posts
I'm planning to soon but things have been such that I've not had any time to work on the car. Things should be quieter in a few weeks and I'll be able to really dig in to it.
study Lambda or Air/Fuel ratios meanwhile. If they are off, you need to figure out why. You also just need to pull all the codes that car may have stored.
 
  • Like
Reactions: ard

·
Officially a BMW Addict
Joined
·
1,025 Posts
Letting a 13 year old car sit for a year is a big issue
 
  • Like
Reactions: zod

·
Super Moderator
Joined
·
8,886 Posts
Swapped the solenoids yesterday and took it for a drive today. It's better but still rough at idle. It's not stalling now though so at least that's progress.
What solenoids did you install, & did you reset the adaptations on the engine. This will make a ig difference. What ever your problem is, it is part of the Vanos system sensors. Disconnecting the MAF & running better, verifies this.
 
1 - 20 of 59 Posts
Top