Poorly Z4M, Idle bounce and poor throttle response/misfire

[Adam D]

Mods: Not sure if this is the best place to post this but since the S54 is only fitted to the M is seems the best place for other M owners to see it/help out Happy for it to be moved if its a problem.

Heya all,

Been having a bit of a rubbish time of late with my Z4M.

Symptoms are:

When dropping to idle the revs fall too low and bounces back up again. If the air conditioning is not running its worse and can sometimes stall if the computer doesnt catch it quick enough. This can be a pain in stop start driving or shuffling up to a roundabout No EML faults are thrown.

From idle if you apply the throttle anything other than a gentle squeeze the engine misses and coughs before the revs zoom up (they zoom up as well as a healthy Z4M I recently compared it to). The stumble is very obvious in the exhaust note.

If you hold moderate revs and flutter the throttle the engine seems to get confused and starts popping through the exhaust, overfuelling/missing? It doesnt seem to follow the throttle input.

Engine slow to start, needing 3-4 turns of the motor from cold.

Solutions/ideas:

So far the dealer has change the AFM - this has made the engine much less raspy and the fuel economy has improved 10-20%, whilst thats nice (although I miss the rasp!) its not touched the idle bounce or issues above. They seem convinced it was fixed and were glowing how it has restored my lost performance... its as flat as a fart compared to the other Z4M I went in yesterday

Google suggests all manner of sensors could be at fault:

Idle control valve
Throttle position sensor
Throttle potentiometer
Exhaust oxygen sensors
Inlet/Exhaust Cam angle sensors
Crank speed sensor
A vanos problem.
Coil packs - although a bit lethargic it will rev out smoothly to redline once this initial stumble is over which makes me think its not a coil pack fault.

Before I go back and express my frustration has anybody had a similar problem or solutions?

Any help is desperately appreciated :headbang:

 

[andysat]

I know i am stating the obvious,but if it were mine i would get it plugged in to read the fault/s.

 

[Beedub]

The misfire would push me towards a coilpack...... Or the pre cat o2 sensor, then again id expect a cel with those.... Are you getting any plausability codes???


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[Adelphi2]

I'm surprised no one has mentioned the spark plugs yet.... Have you had these changed?

 

[srhutch]

Others have reported this same issue recently without finding the reason.

Must be an issue on the M3 also so might be worth looking on one of those forums.

I assume it's under warranty.

 

[Adam D]

I know i am stating the obvious,but if it were mine i would get it plugged in to read the fault/s.

I'm told they already did that to find the AFM problem, maybe they were not exhaustive and stopped when they found one fault/fix Definately going to request this though as I have the comprehensive bmw warantee

I'm surprised no one has mentioned the spark plugs yet.... Have you had these changed?

Original plugs with 33k on them.

The misfire would push me towards a coilpack...... Or the pre cat o2 sensor, then again id expect a cel with those.... Are you getting any plausability codes???

No CEL/EML lights suprisingly

If it was out of warantee the coil packs and spark plugs would be swapped out at my cost for peace of mind.

 

[BMWZ4MC]

Mine coughs and splutters occasionally, and very rarely it will dip below idle as you describe. I think it has even stalled once or twice. However, 99% of the time it runs absolutely normally. I wonder if mine is running a little rich as it really pops back throught the exhausts these days, and the tail pipes are rapidly sooted after I wash the car. I can't be sure though as I've replaced my OEM back boxes that had very dirty tail pipes with noisy Remus back boxes that have very shiny pipes!
On the other thread (http://www.z4-forum.com/forum/viewtopic.php?f=9&t=32043&start=30), you said that changing the MAF solved the problem temporarily. Have you modified your air intake in any way that could be contaminating the MAF filament, eg oiled filter?

 

[exdos]

Have you tried resetting the throttle and then taking the car for a good blast to get the cats nice and hot? See: http://www.z4-forum.com/forum/viewtopic.php?f=32&t=195&hilit=throttle+reset

What happens if you put it in Sport Mode?

Are all the small hoses connected to the plenum in place?

If none of those things rectify the problem then you need to hook it up to diagnostics and my money would be on the Throttle Position Sensor at fault. See Item 2 (Part Number 13637840383) here: http://www.realoem.com/bmw/showparts.do?model=DU92&mospid=49422&btnr=13_0911&hg=13&fg=15

 

[RubyBlueZ4MC]

Adam sorry that your having these problems.. Although I do like the references to the "healthy" Z4M you compared it to Glad you enjoyed the ride! Hope things get sorted.

 

[Adelphi2]

Could also be dirty fuel. I had similair issues with my old 3 series and it turned out to be that Tesco fuel was the culprit. Engine kept dropping power and performing poorly. Had it run it down to empty and then fill it up to the max with shell power.

 

[ga41]

Mine is STILL having similar issues. New O2 sensors, new MAF sensor, replaced catalysts with used ones (had to anyway because they were indeed shot), new coils, new sparks and the problem is still there. The mechanic now thinks he's tracked it down to a problem with the throttle bodies.

About a year ago my throttle actuator had gone, developed a fault and after 4.5k RPM it would stop working, ordered a new part and as i was still using the local BMW dealership for my services and whatnot I took it to them to install it. Now to do that they have to remove the airbox and intake manifold. I first started noticing issues as described by the original poster after this installation, it wasn't anything severe at first but it's gotten slightly worse since then to the point where it's stalled once or twice in traffic and the hesitation up till about 3k is very noticeable, sort of like turbo lag.

Apparently as the dealer was installing this throttle actuator they somehow fucked up the throttle body settings/adjustments whatever it's called, according to my mechanic. After eliminating other options he's come to the conclusion that it's down to the throttle bodies. He even re-installed my stock exhausts (i've had the much freer-flowing RPI's) to see if it's a difference in back-pressure than stock that might cause this.

He hooked up his Autologic diagnostic thingy and ran a test on the throttle bodies, they can be set at 0 degrees and 90 degrees right from the diagnostic computer, at 0 degrees my TB's where indeed 0 degrees, at the 90 degree setting they only opened 76 degrees according to the computer. He also saw that the pull rod that's moving the TB's seemed damaged/bent/not right so he ordered a new one. That didn't fix it either so he tried 2 other S54 throttle actuators that he had in the shop (one was from a fully healthy CSL owned by a friend of ours) and even with those they wouldn't open more than 76 degrees. His only conclusion then was that the dealer screwed up their adjustments somehow.

On Monday he's starting work to re-adjust them properly. An apparently long and difficult procedure from what he and others tell me.

This is my story so far with this, i don't know if it applies in Adam D's case but the symptoms are damn near identical. When i get this thing sorted out i'll definitely update you all.

 

[SweetRide]

Holy horn, what a lot of work/trouble. An RPM drop at idle after a hot run is pretty common w/ Z4M's, sometimes even stalling. Nature of the beast. Some have said it happens more when the tank is below 1/4. Shouldn't be happening all the time tho. Best of luck finding the ghost in the machine

 

[Gargybloke]

I must be just lucky then but I have never noticed any stalling or ide rpm drops. Is it really a common thing?

 

[ga41]

I don't think it is. As i said i only really started noticing this after the new throttle actuator was installed. It might've done it before but definitely not as severe. If you don't notice anything like that on yours then it's perfectly healthy i guess!

 

[Darren Slone]

Sorry to hear your troubles , my car was lumpy at low revs around 34K miles so changed the spark plugs and resolved the issue, hope you get yours fixed soon

 

[2dogs]

Mine has some odd things, after a run turn off come back say 30min ish restart and leave ticking over and after about 30 sec it start to misfire, coughs and splutters blip the throttle all back good.
Also notice last week after queuing for petrol turning the engine on and off many time that on the way back home each time I stopped it would dip below idle or stall this happen for about 1/4 of a mile
then all good again. :?

 

[exdos]

A quick question to all those who have idle problems; Do you use ordinary 95 RON Petrol or does this problem still happen with the higher octane fuels, such as BP Ultimate (97 RON), Shell V-Power (98 RON) or Tesco Premium (99 RON)?

 

[Adam D]

Thanks for the really helpful replies - thats why this forum is brilliant! Ga41 I will definately show the dealer your post to give them some food for thought!

I forgot to mention this earlier but the first time I reported this issue the dealer mentioned one of the throttles was out of alignment and they did something to correct it... this was before the AFM was changed which was since told to be faulty (which would have been broken at that time but overlooked :headbang: ) I believe the AFM has been knackered the whole time I owned the car since buying it from them under AUC, it always had poor MPG and popped and banged when warm with very sooty exhaust tips.

I think they need to fully investigate the ignition components first to rule out a simple fix (coil pack breakdown or knackered plug - bearing in mind its been running rich the whole year since they sold it to me - the exhaust tips are so black inside). I would have thought a weak spark/faulty coilpack would throw an EML light?

Next I would expect a full dianostic of the throttle sensors, pedal and butterflies/linkage, replacing faulty parts and recallibrating to correct trim. It certainly doesn't feel like I get full throttle as the car behaves better when in sport mode in terms of pull, its as if I cannot get full throttle opening in normal mode.

Quite frankly I'm annoyed that a AUC car has had to go back with so many problems in a single year of ownership, its difficult to get the time off work to deal with it :headbang: :headbang: :headbang: :headbang:

I will try some BP ultimate instead of Vpower/Tesco99

 

[exdos]

Adam D,

Have you tried running the car with the TPS disconnected, and if so, do you still have the idling problems?

 

[ga41]

For reference i've been running it with 98 octane petrol for the last 2 years or so with no other faults. I've only put in 95 once or twice in the 3 years that i've had it when i couldn't find 98...

Also, i just drove the car a bit and it did seem better but it was only a short town drive so not definitive but Adam D, i've got even more complications for you...... He now removed the throttle bodies altogether and tried to get the actuator to reach 90 degrees without being attached to the throttle bodies, it still read 76... He replaced 2 other sensors relating to the throttle bodies and actuator (cannot remember their proper names nor parts numbers.. ) and still the same. They now think it's something with the car's ECU. Note that i don't have a remap or anything.

As i said, i drove it today for a couple of miles, as i wanted to attend a BMW M cars meet and it really did seem a lot better, almost no hesitation at low revs but when cranking the car up from cold it did splutter and "coughed" a bit.. Couldn't push the car to redline or anything either so take from it what you will.

I will keep you all updated.