[WildWilly1100]

Hi guys, Kinda new here and new to the F10, owned for about a year now. In the last few months, when starting the car cold, RPM will hit 1100-1200, then drop to 500 and a few seconds later, rev up to 1500, then settle in back at 1000 or so and away you go. Only does it on cold (not winter cold) start. Any ideas??

115,000 kms, N55.

Thanks.

[BurrNinja]

Mine occasionally on cold starts revs to 1800 down to 1000 back up and down a few times then settles out. I've talked to a Bmw tech I personally know he said it's normal with the n55 not sure why it is the case. If this is what you mean? I've tried putting the car in drive to see if it triggers any cel and nothing it just stumbles and smoothes out.

[WildWilly1100]

that is more or less what mine does, but it drops to 500. Once you're going for the day, it won't do it again. Maybe time for new spark plugs?

[Trainwreck914]

My wife's 2014 f15 with n55 does the same only on cold start. Afterward doesn't happen. My 2011 f10 n55 never does this

[BurrNinja]

Originally Posted by WildWilly1100

that is more or less what mine does, but it drops to 500. Once you're going for the day, it won't do it again. Maybe time for new spark plugs?

I have new spark plugs less then 7k on them. Did not solve issue.

[WildWilly1100]

Originally Posted by BurrNinja

I have new spark plugs less then 7k on them. Did not solve issue.

That's a bummer, it's only started since about 110K, trying to figure out what happened.

[BurrNinja]

Originally Posted by WildWilly1100

That's a bummer, it's only started since about 110K, trying to figure out what happened.

Yeah mine has been going on since I've gotten the car at 84k now at 103k.

[paul223]

It is time clean Intake valves if it has not been done before

[BurrNinja]

Originally Posted by paul223

It is time clean Intake valves if it has not been done before

One of these days I wanna remove my intake and inspect them. I might just do myself with some cleaner spray and dry it up.

[WildWilly1100]

Originally Posted by paul223

It is time clean Intake valves if it has not been done before

From what I understand that is a pretty big job, is that correct?

[WildWilly1100]

Maybe I'll try this before I look at walnut blasting. Worth a try for $20, me thinks.

[BurrNinja]

Originally Posted by WildWilly1100

Maybe I'll try this before I look at walnut blasting. Worth a try for $20, me thinks.

One thing to know, if you do spray any cleaning chemical in the engine, make sure its directly at the throttle body. Do not pass through the entire intake.

[WildWilly1100]

Originally Posted by BurrNinja

One thing to know, if you do spray any cleaning chemical in the engine, make sure its directly at the throttle body. Do not pass through the entire intake.

So what this guy did, by loosening the clamp, is that OK?

[BurrNinja]

Originally Posted by WildWilly1100

So what this guy did, by loosening the clamp, is that OK?

Yeah thats perfectly fine. as long as there's not a major gap in it, otherwise it will misfire

[WildWilly1100]

Originally Posted by BurrNinja

Yeah thats perfectly fine. as long as there's not a major gap in it, otherwise it will misfire

OK, I'll open it up just enough to get the red tube in and then tighten it back up before starting. Thanks. I'll report back if it fixes my start up issue.

[BurrNinja]

Originally Posted by WildWilly1100

OK, I'll open it up just enough to get the red tube in and then tighten it back up before starting. Thanks. I'll report back if it fixes my start up issue.

I tried doing the Walmart fuel injection cleaning and the hard plastic didn't have enough play to fit. Caused a heavy misfire

[Trainwreck914]

Walnut blasting is not that hard if you have the right tools. It's a bit tedious first go around to remove the intake manifold. But after doing it once. I can have it out in about 20 min now.

You'll need the adapter Bmw specific $75
Media blast kit (harbor freight) $30
Walnut shells (fine) harbor freight $20
A shop vac
And a compressor.

Can't stress enough that you MUST make sure the valve is in the closed position when you blast. You can "bump" the starter to switch valves. And blast for about 30 seconds each.

[WildWilly1100]

Just did the treatment, the car is sitting for 10 minutes now. Will go for a gentle drive shortly. Man, it takes a long time bent over the front of the car to empty a can of cleaner one squirt at a time! Will know tomorrow if it helped the cold start issue. Fingers crossed.

[WildWilly1100]

Went for a drive, lots of smoke out the back, engine light came on, ran like crap for a few minutes. Pulled into a parking lot, turned it off, then started up again and drove away, nice and smooth now, will know tomorrow if the cold start issue is better.

[BurrNinja]

Originally Posted by WildWilly1100

Went for a drive, lots of smoke out the back, engine light came on, ran like crap for a few minutes. Pulled into a parking lot, turned it off, then started up again and drove away, nice and smooth now, will know tomorrow if the cold start issue is better.

Signs of a lot of smoke is a good thing doing its just. Let me know!

[WildWilly1100]

Well this morning, started the car and the RPM only dropped to just under 1000 rpm, so that is a definite improvement over the original drop to almost 500 rpm and occasionally would stall out. Maybe do another treatment in a few weeks.

[SWFLf10]

Another thing to look into is the vanos solenoids mounted to the front of the engine. I know on a previous BMW of mine that they caused an RPM issue when starting the car when they were starting to go bad.