siavosh

Hey Guys,

I've just bought an 04 545i and this is my first V8 bimmer since I've always had the in line 6s on 3 series. I know that rough Idling is pretty common in these engines and I've read hundreds of forums about it but none of them seem to experience what I experience.

So this is what happens:
On a cold start, the car starts absolutely fine without any problems or misfiring or rough idling until it gets to working temp (mine works between 103-107).
Then when you start the car back on with a warm engine, it idles rough for a few seconds and then it stabilizes and then there are no issues after that. Sometimes though, the idle gets really rough and check engine light comes on and also engine malfunction on idrive but if I turn the engine off and back on everything works fine and no check engine anymore.

Does anyone have an idea of what can possibly be wrong that the engine is playing this game with me?

Since its only for a couple seconds after starting I cant even catch it on the scanner since it takes longer than that for the scanner to initialize.

Cheers,
Siavoh

e6t.lab.rat

Whenever I have idling issues the first thing I would check are the vacuum hoses and the intake.

Check your air filter (could be restricted) and intake tube to make sure there are no open airways along the path to the throttle body. Clean out your MAF if you haven't done so. You'd be amazed how a dirty MAF can greatly affect performance. Start here first and report back. Good luck.

siavosh

Hey,

Sorry for the extremely delayed response. I've been super busy and I finally found some time to open her up today and take a look.

Although I bought the car with a low mileage for its year but apparently the previous owner(S) haven't done a good job with maintenance.

- opened up the air filter and it was so old that I was cracked and there were leaves underneath the filter. God knows how long that filter has been sitting there. Replaced with MAHLE OEM filter.

- MAF didn't seem dusty or dirty but I sprayed and cleaned it.

- spark plugs were the original BMW NGK plugs. (The ones with just BMW and NGK writing on it that comes on the car from factory) and they were sooooo done. Replaced 4 of them but couldn't get to the other 4 which are oddly located. (Gotta search for DIYs on how to do that)

These done the car starts up way smoother and idles perfectly.

By the way, does anyone know whats the operating temperature for the N62B44 engine? Mine moves between 105 to 110 and I feel like it's too hot.

Sebbike

Hi,
The operating temperature of the N62 is a little bit high, it's normal for this engine, mine is also between 103 and 107 degrees

cmyachtie

Agree that's probably too high, dug out me latest temps from January and it's at 101.25C
Since it appears car got neglected some, would recommend to do a coolant flush ASAP.....hope temp comes down after that.

I stand corrected.......
Did some research on this and Bob is right your temps are quite OK for the 545 running at those temps, they run quite hot and with that being said according to your #2 post I suspect you might have 12 yr old coolant in your engine and still recommend to drain it asap....

FormerE30Owner

Actually, those temperatures look quite normal and certainly not a sign of a fouled cooling system. The temperature control system is doing its job. If the temperature starts to get over 120 C, then I would start to worry.

Salut, Bob P.

siavosh

Bob,

What temp does your engine run at?

FormerE30Owner

Its been a long time since I looked, but never gets higher than 110 C.
Having the temperature vary is normal, as this indicates that the thermostat is operating properly, so don't get too hung up on the running temperature unless the heater doesn't heat or you get a high coolant temperature alarm. 120 C is the max temperature and is probably when the alarms will happen.

Thermo-dynamically the higher the engine temperature the more efficiently the engine runs, but there are limits to the "health" of some engine parts - gaskets, seals etc..

Flushing your coolant is never a bad idea, however, to avoid corrosion and fouling of the system.

Salut, Bob P.

siavosh

I guess I'm being too ocd about it. It goes up to 110 while the car is stopped and immediately when I start moving it drops to 105.
I guess it has also something to do with the idle speed of these V8s as they idle so low that it reduces the flow and pressure from the water pump.
I'm gonna stop bringing the temp gauge up on OBD and enjoy the ride hehe

FormerE30Owner

Actually the reason that the temperature rises to 110 C at idle has more to do with the fact that there is less air going through the radiator and a new equilibrium is established at 110 C. If the temperature continues to rise at idle, the electric fan will come on if it hasn't already. Once you start moving there is more than enough air going through the radiator and, depending its temperature, the fan is no longer necessary.

Salut, Bob P.