Lazy, Jerky, Horrible Throttle

N

nichollsz4

Member
Hello fellow Z4m owners,

I've started a thread to see if anyone has had any issues, as titled above, that might be similar to what I'm currently going through.

I've had my Z4m for a little over a month now and other than the usual niggles, it's been fine. I have however noticed a lazy throttle response and horrendous jerk when changing gear. (Like dumping the clutch) its just impossible to drive smoothly. In fact, it drives better when cold!

Diagnostics shows error codes for MAF sensor and throttle body sensor, but I have unplugged them and cleaned them down.

I'm booking the car back in the garage to be looked at further, but I'm just wondering if anyone else had a similar problem and what the fix was?

Thanks,
 
Tried resetting the throttle?
Easy,
10sec ign on
10s ign off
10s ign on
Start engine
Turn off.
(Never touch pedals)

I have to do this once a month or so.. Funny little car this!
 
Argenta said:
Tried resetting the throttle?
Easy,
10sec ign on
10s ign off
10s ign on
Start engine
Turn off.
(Never touch pedals)

I have to do this once a month or so.. Funny little car this!
Click to expand...
I've never had to do this with mine nor AFAIK has my pal with another, so I'd suggest there's something amiss with yours.

nichollsz4 said:
Haven't tried this yet. How long do I leave the engine running for before turning off?
Click to expand...
You don't need to run the engine before doing this, just follow his instructions when you go to start the car.
Eta sorry misunderstood your post. You do not need to run the engine for any length of time after doing this, the reset command happens before you start the engine.
 
nichollsz4 said:
Diagnostics shows error codes for MAF sensor and throttle body sensor, but I have unplugged them and cleaned them down.
Click to expand...

Is their a local member you could try swapping these parts with? If not then the error codes are probably right and you'll need to buy new ones.
 
Pures3 said:
Could it be the clutch delay valve?
Click to expand...

CDV isn't really noticeable TBH so no not with the symptoms described.

With what you've said, it sounds like the throttle body valves are shutting off which does give a nasty jerk like the clutch dumping or a fuel cut type feel, although not sure why it would be when changing gear, might be coincidence?

Does point to an issue with potentially the TP sensors though, if they read incorrectly or one doesn't match up with the other (one on the throttle actuator and one on the throttle valve 'bar') then it could lead to it shutting off suddenly to protect the engine at certain throttle / rpm situations, hence the jerk. Also would give poor throttle response as described.
I would say look at the TP sensors first. Cheapest and easiest fix, and if they've never been changed is well worth doing anyway and then go from there.
Also, what diagnostics are you using?
 
One of the tps sensors or possibly the throttle actuator would be my first thought.
The maf may also be the culprit, cleaning it won't necessarily help. Try unplugging the maf and see how it runs (it should run fine-ish without it), if that resolves it somewhat then maf will need replacing.
 
AndyBeech said:
Does point to an issue with potentially the TP sensors though
Click to expand...

Agreed, although only slightly similar symptoms to what I experienced when my front TPS went down. The main thing I noticed was a lack of willingness to rev, plus the warning light with the specific TPS failure code.
 
Hi my car is going to BMW Carteya in Algeciras on Monday as I have a slight problem at idle revs when I go to drive off the revs dip slightly when I apply light throttle making it very easy to stall. These cars seem to suffer from an issue that doesn't affect the equivalent M3. I have no CEL and no codes so its not clear enough to me to be able to diagnose adequately. Loads of threads around on it but nothing conclusive anywhere unfortunately so rather than follow the common parts replacement and cleaning and see if it works I am just going to take it to BMW and tell them to sort it out!! I would imagine the possibilities are ICV, TPS, lambda sensor, fuel filter, vacuum leak or something like that. Going to have a few blemishes on paint sorted out at the same time. I'll let you know what they do to mine.

Just to try and relate my issue back to yours, its not identical - mine only has an issue with a rev dip from idle, beyond 1000rpm I have no hesitation or any other issue. But that's not to say mine isn't an issue that could progress into something worse if not resolved.
 
Apologies for the delay responding. Its been a long week.

Bit of an update...

The car was diagnosed with a Snap on diagnostics device. I have been driving since clearing the faults from my initial post for over a week now and there has been no change in the car. It has been plugged back in today and no faults were found It has also been plugged into BMW diagnostics which also found no faults. The other faults found previously were a result of me unplugging things whilst the car was running. (miss diagnosis)

Whilst plugged in, the throttle body sensor was tested, which found no problems and something specific (forget what the tech called it) was reset relating to throttle position, etc. checked idle and smooth running and all looked good.

The only thing that the tech did say that he wasn't get a good reading from the throttle sensor, but it was clearly working. If the TS was on the blink, its more than likely a fault would register.

Looking at whats been checked and with no fault codes to go off, I can only surmise that the issue may be a result of a bad MAF sensor. BMW of this period were terrible for MAF sensors being end of life, and the ECU failing to flag it. I have actually unplugged the MAF for now to see what changes I get. So far nothing has changed. I expect to see the EML to pop up as I continue to use the car and will be interesting to see how the car changes, if at all.

Question, there is a 'secret' menu you can access from on the cluster where you can bring up the MAF sensor. Form here you can see the MAF sensor reading which i'm told shouldn't drop below a certain number. Does anyone know the process to access the menu and the figure the MAF sensor shouldn't drop below?

Thanks,
 
Sam1977 said:
Hi my car is going to BMW Carteya in Algeciras on Monday as I have a slight problem at idle revs when I go to drive off the revs dip slightly when I apply light throttle making it very easy to stall. These cars seem to suffer from an issue that doesn't affect the equivalent M3. I have no CEL and no codes so its not clear enough to me to be able to diagnose adequately. Loads of threads around on it but nothing conclusive anywhere unfortunately so rather than follow the common parts replacement and cleaning and see if it works I am just going to take it to BMW and tell them to sort it out!! I would imagine the possibilities are ICV, TPS, lambda sensor, fuel filter, vacuum leak or something like that. Going to have a few blemishes on paint sorted out at the same time. I'll let you know what they do to mine.

Just to try and relate my issue back to yours, its not identical - mine only has an issue with a rev dip from idle, beyond 1000rpm I have no hesitation or any other issue. But that's not to say mine isn't an issue that could progress into something worse if not resolved.
Click to expand...

Is this under warranty?
 
Sam1977 said:
Hi my car is going to BMW Carteya in Algeciras on Monday as I have a slight problem at idle revs when I go to drive off the revs dip slightly when I apply light throttle making it very easy to stall. These cars seem to suffer from an issue that doesn't affect the equivalent M3. I have no CEL and no codes so its not clear enough to me to be able to diagnose adequately. Loads of threads around on it but nothing conclusive anywhere unfortunately so rather than follow the common parts replacement and cleaning and see if it works I am just going to take it to BMW and tell them to sort it out!! I would imagine the possibilities are ICV, TPS, lambda sensor, fuel filter, vacuum leak or something like that. Going to have a few blemishes on paint sorted out at the same time. I'll let you know what they do to mine.

Just to try and relate my issue back to yours, its not identical - mine only has an issue with a rev dip from idle, beyond 1000rpm I have no hesitation or any other issue. But that's not to say mine isn't an issue that could progress into something worse if not resolved.
Click to expand...

Hi Sam,

My car isn't easy to stall, and I haven't paid much attention to where the revs dip. I'm usually changing gear between 2-3k but notice it allot smoother when changing lower than 2k

I'm starting with a new MAF, which I'd be tempted to do in your position too. My understanding is the ECU works out the correct fuel and air mixture demand from the sensors. So imagine if that sensor was tired and giving the wrong information such as providing lower air than what's required. Your MAF could be giving false reading that will cause your car to want to stall.

This my understanding, so might be wildly inaccurate. Appreciate you just wanting it fixing, but with no codes like yourself, all that BMW will do is troubleshoot further. With no warranty, that could be a heavy bill.

I'm running mine with the MAF unplugged, so will let you know of any changes/developments.
 
Thanks for the input. Presumably now you disconnected MAF you have CEL on - can that simply be reset by standard OBDII scan tools? I have a few - Foxwell, a specific BMW one that I bought on Amazon and another cheapo one. I am tempted to try and disconnect the MAF as you have but only want to do that if I know I can reset the CEL. Can you confirm that?

The other possibilities - TPS/ICV I don't really want to get into doing myself - I could do it, and have the tools and know-how but I just don't have the time to spend doing it.

However the MAF is a 2 second job - just worried about the reset! I'd appreciate your advice on that as the appointment at BMW has been put back to Tuesday so I have time: keep me posted on yours and I will do likewise, see if we can get these cars tip top!!

All the best
Sam.
 
The EML for MAF will turn itself off straight away once plugged back in, or at worst after a few runs. Trouble with taking out the MAF for diagnosis is the car will run on its Alpha-N map which disregards certain readings from other sensors so won't neccasirly mean the MAF is the fault if it goes away if you get my drift.
Worth a shot though, I've changed MAF before and it didn't solve the rev dip issue I had. If you change the MAF you should also delete the adaptations in the DME so it can relearn its running values otherwise it'll just use the ones it had prior to the change and will take a while to readapt itself to any change of parts.
TPS issues won't always trigger the EML light unless it's really knackered, if it's a bit 'lazy' the car may just work around it rather than throw a light, in my experience anyway....Lots of people have changed the TPS sensor to good affect with no EML light showing.

Also consider VANOS issues would contribute to poor idle and reduced low down power output.

Edit: getting to the TPS/ICV is an easy job, can be done in about an hour or so, once you've done it once it's worth doing as you can carb clean all the butterfly valves on the throttle bodies, ICV, actuator and assosciated springs. May or may not help but can't hurt.
 
Thanks Andy - I was put off on the TPS/ICV thing based on an article from Pelican Parts that said 5 hours!! I must admit having had the whole inlet manifold and throttle body out more than once on my 330 Time Attack car in much less time I did scratch my head at that!

Okay I understand how a MAF works and interacts with DME so your caveat aside I will give that a bash and see.

To clarify on my issue which seems slightly different from that of the OP, my idle is fine, my acceleration above 1000rpm is fine, my issue is a rev dip on light throttle which makes it easy to stall and it is completely consistent/persistent and stabbing the throttle in neutral I have the rev dip and a slight cough before it revs clean over 1000. Based on that (and I don't want to hijack the OP's thread here ...) whats your advice?

Thanks all
Sam.
 
Just to add to this,

My car feels absolutely fine performance wise. It idles fine and doesn't ever feel like it's going to stall. It's just got an awful throttle response, which, when pottering around, is just awful drive.

With the MAF sensor disconnected, EML came on and nothing else. No change in how the car drives. I've plugged it back in and waiting for the light to go off. Will let you know how I get on.
 
EML light does go off once plugged back in. Probably takes up to 30 miles before the light goes off.

Throughout the time I've had the MAF unplugged I saw no difference at all. I'll likely replace this first, then the TPS. I have access to diagnostic tools so willl reset the adaptations once replaced.
 
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