Not responding to throttle input and has heavily oscillating idle

R

Rene_Z4MC

Member
Hi Guys,

This morning right after initial crank the revs started to fluctuate between 500 and 1500RPM with a frequency of about a Hertz (so vroom..vroom..vroom..vroom), there is not response to the throttle input. Tried a few re-starts but issue remained so the car is undrivable :(
Drove it yesterday without any issues (its my daily)

Any ideas? Know issue? Any advice is welcome

Regards,
René
 
Sounds like your throttlebody has knocked off for Christmas! :lol:

Let me dig out my thread which might help you.......

edit:
here ya go fella. Might help. Might not. But I reckon you've got the same issue I had.
Good luck and keep us posted re. the outcome.... :thumbsup:

http://www.z4-forum.com/forum/viewtopic.php?f=3&t=90194&hilit=tantrum

(crikey - that epic thread has had over 5000 views! :o )

edit edit:
essentially, I replaced the throttlebody with a cheap 2nd hand one off ebay and it fixed the issue. (there were a few other separate issues to sort too - it was decanting oil like oil was going out of fashion :lol: )
the used one came off an X5 apparently. same spec. was my intention to buy a new one as the 2nd hander was intended as a test to cancel out what I thought the underlying issue was. It's still going strong however....
Hence, get yourself a cheap second hand one off fleabay and swap in urself. as you'll see from the thread it was an epic challenge for me, not being a mechanic etc. but the reward factor once it was back up and running was...and still is immensely satisfying! :)

edit edit edit:
oh i see it's an M.
well, forget the above maybe.... :oops: :rofl:
 
Rene_Z4MC said:
Hi Guys,

This morning right after initial crank the revs started to fluctuate between 500 and 1500RPM with a frequency of about a Hertz (so vroom..vroom..vroom..vroom), there is not response to the throttle input. Tried a few re-starts but issue remained so the car is undrivable :(
Drove it yesterday without any issues (its my daily)

Any ideas? Know issue? Any advice is welcome

Regards,
René
Click to expand...

Any engine warning lights, DTC light etc? (Almost certainly will have....)

Sounds like a problem with the 'de-bouncing' phase, when you turn the key to start the car the throttle bodies do a quick initialization check, if this fails you get what you've described above.
Check the throttle bar linkage, make sure it is working and isn't getting stuck on anything (Do you use jubilee clips on the TB's or the standard BMW rings?), shouldn't do if you aren't using jubilee clips but check anyway. Could also be a faulty TPS sensor though would have to be completely gone I would imagine to cause this issue. Any leaks in the air intake after the MAF sensor.
If there's nothing obvious, you might have to take off the air intake / plenum to get to the throttle actuator and see if anything's going on down there.
Diagnostics would be useful if you have them as well! If you have INPA you can manually activate the throttle actuator (with the engine off) to open at different percentages which can massively narrow down the issue.
 
@Chris_D
Thanks for the input, read into the thread but since this is an M it does not really apply (like you said ;).

@AndyBeech
Makes a lot of sense, thanks for that info.
I still have the default BMW clips, did clean the IACV a few years back (hence profile pic) so i know my way around there, will check it out tonight and keep you guys updated.
 
Rene_Z4MC said:
@AndyBeech
Makes a lot of sense, thanks for that info.
I still have the default BMW clips, did clean the IACV a few years back (hence profile pic) so i know my way around there, will check it out tonight and keep you guys updated.
Click to expand...

I figured from you're profile pic you might know you're way around, useful when you have problems like these!

I would be almost certain it's something to do with throttle bodies / linkage / actuator. I had exactly the same problem not long ago and it was the linkage getting stuck on a jubilee clip on the way down. You don't use those so rules that out, but the same symptoms.

If you have to go as far as taking the plenum off and getting to the actuator, a good way to test it is turn the key to the on position without starting the engine which will put it through it's initialization test. You should here the throttle body butterflies open and quickly snap shut along with an electrical buzzing noise by the actuator. That would at least confirm the actuator is working (though doesn't completely rule out an issue here). If any warning lights you had at this stage go out as well you know there's an issue from the air plenum backwards rather than with the TB's and beyond.

Good luck!
 
Sounds to me extremely likely to be one of the TPS', hopefully for you the one at the front of the engine (2min fix), otherwise it could be the one near the actuator underneath the airbox (same part for both). Have you scanned the car for fault codes?
 
TomK said:
Sounds to me extremely likely to be one of the TPS', hopefully for you the one at the front of the engine (2min fix), otherwise it could be the one near the actuator underneath the airbox (same part for both). Have you scanned the car for fault codes?
Click to expand...

I have replaced these in the past, still have the old ones lying around so I can do a quick swap.
Not scanned for fault codes yet and to be honest I'm not exactly sure how, I have a very old laptop with very old DIS software and an OBD plug but never managed to get it properly working on the ///M (it does work however on my friends e46 320d). What is nowadays the best/easiest way to scan fault codes on the Z4M?
 
Easiest way to scan is with a bluetooth ELM327 OBD dongle and the use torque (android) or dash command (i think for mac). Total cost about £5.
you're obviously a bit more limited than using dis/inpa etc but you can scan for all and reset most codes with Torque.
http://www.ebay.co.uk/itm/Mini-ELM327-OBD2-II-Bluetooth-Diagnostic-Car-Auto-Interface-Scanner-Tool-FTKS-/142266709066?_trksid=p2385738.m4383.l4275.c10
 
I'd be looking at TPS too given the fluctuating revs, and as TomK has mentioned hopefully the one at the front of the engine otherwise you'll need to get down to the actuator below the inlet! The throttle pedal itself has a TPS, not sure if it's serviceable or whether it's a new/recon pedal assembly?

My old E46 M3 would throw an EML when cold as it failed the throttle initialisation (no fluctuating revs though)... this was caused by cold grease/dirt in the springs on the throttle butterflies which i didn't realise until after changing the TPS! Might be worth giving them a clean up first as that will cost nothing but a bit of time!?

But defo scan for codes as hopefully it will steer you in the right direction
 
Quick update:
Came home, started the car to drive it into the garage and it just worked! :lol:
Engine light still on though and I know that there must be something wrong, so will dig for the root cause and update y'all if found.
 
Just be aware if you're out in it, it might suddenly happen again at the worst moment, like miles from home like it did with me before I fixed it :rofl:

If you're around the Reading area at all and need diagnostic equipment help, give me a shout.
 
Once in a while, my ///M would behave as you describe then return to normal running after three restarts. On one occasion, it went into limp mode and would not return to normal running. The problem turned out to be a faulty cam position sensor. That was eight years ago and it’s been fine since.
 
Another quick update:
Did an ECU read-out with OBD Auto Doctor (trial version) and found P1417 which is indeed throttle control related.

Possible causes
- Faulty Throttle control
- Throttle control harness is open or shorted
- Throttle control circuit poor electrical conenction

Like said before the symtoms are currently no longer there and I've checked TPS connection etc but didn't find any issues.
Not really a satisfying outcome but will use the car for now (engine light is off again) and see what happens.
Will keep you updated :)
 
Just a short update for future reference;
End of December I've cleaned the throttle bodies and IACV, been using the car on a daily basis since and did not have any issues anymore. I think that dirty/stuck throttle body/linkage must have been the root cause.
Thanks for all your support
 
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