SOLVED: 4.6is with "throttle briefly jammed"
 

Hi guys. Three times now when starting the car after it had cooled down (about 2-3 hours of being parked), the car would crank but the RPMs would quickly drop back to 0. Starting it up again and the RPMs would fluctuate for a few minutes before going back to a steady RPM.

I went by the mechanic to have it checked, who got the "throttle briefly jammed" error code. He adviced me to take off the throttle body and clean it off with brake cleaner and a soft brush. On the forum I read a lot about the throttle position sensor. Any advice on what would be the best next step, before I start cleaning the throttle body?

P.S. I also read somewhere that a rip in the intake rubber would also cause this. The mechanic checked for vacuum leaks but didn't find any

I never experienced this issue on my 4.6iS but it did happen to my M62 powered 540i. It is a thing, TB failures are a "known issue" with these engines. Hell it even happened to Jeremy Clarkson in the Nile Special. May have been scripted may not, we'll never know.

Any shop that has an oscilloscope can determine TB swing spikes at the TPS

Step one remove TB clean, replace any gaskets, reinstall and road test

The big issue on the 4.8 is the throttle positioning sensor (TPS) is built into the throttle body and everything is drive by wire. As more and more crud builds up on the Throttle body plate, the more likely it is to stick in the idle position. Carb Cleaner, that is O2 sensor safe, and a tooth brush will clean off the crud. Check your intake for oil that is coming out of the vapor separator tubes. Those are the two fat hoses left and right of the TB. Also replace your Engine Crankcase Vent Valve BMW PN: 11127547058 QTY: 2.

I'll be sure to check out that episode, don't think I've seen it! But isn't this the M52 engine? Does it use the same throttle body?

Thanks for the write up Stephen.

I took out the throttle body and took a quick video of the insides before gently cleaning it with a (new/clean) toothbrush, brake cleaner and some patience. This is the "before" video, and afterwards it was totally clean of any grime (didn't take an "after" photo/video).

https://www.youtube.com/shorts/T0pUm3EnbhA

After cleaning it seems like - so far - the RPMs doesn't fluctuate anymore. I've started the car about 10 times (with 15-30 minutes inbetween) and the RPM was completely steady each and every time. So far so good, we'll see if it keeps up. If the issue pops up again I'll be sure to clear all faultcodes and see if it pops up again.

As for the two fat hoses left and right of the throttlebody, those have been replaced very recently by the previous owner. I don't think they will show anything.

540i e39 is the 4.4 M62, same basic engine as the 4.6.

The issue has been solved by cleaning out the throttle body, the RPM is always steady now! :-)

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Congrats. The crud is a little oil residue, fuel mix from the cyl on shut down, and dirt getting past the air filter system. All dries every time you shut off the engine after a road trip. The build up is always greater if there is more of the crap entering the intake system from poor connections, blow buy, and the oil separators failing. The back side of the valve is where it all collects.

I have cheered too early. It happened again a couple of hours ago, even with the clean throttle body. I think it's best to get another reading to see if any fault causes have popped up.

I can get a secondhand throttle body for rather cheap, perhaps it's a better option to get it secondhand and replace the rubbers. What do you guys think?

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Throttle bodies rarely fail.

Open your DME box, remove the 3rd connector on the DME (Or just all of them) and inspect the connectors for oil/coolant residue. Yes you read that right.

It's a known issue for the M62 and can cause false positive codes related to the TB.

If you do find anything, clean it up, start the car, and HOLD the rpms for a good min at ~ 1500 (just holding it is the core here) so the car establishes control again for idle. Weird but it happens sometimes.

I will try to find some time for this next week I hope! Thanks for the advice, I remember reading about that DME box a couple times before.