Rev dip issue

S

Sam1977

Member
 Spain
Dear all

I have started a new thread because I ended up chipping in on someone elses issue which seems different from my own and I don't want to continue to hijack or confuse that matter.

Here is my issue:

With cold start and the revs at 1000rpm if I blip the throttle in neutral it revs up clean. Once warm and the RPM's drop to about 800rpm it idles perfectly smooth and consistent but if I blip the throttle there is a very momentary drop in revs before it then revs clean up. Doesnt stall. If instead of blipping (or stabbing - whatever you want to call it) I press the throttle gently it is slightly stuttery for the first 100 maybe 200rpm over idle.

If I feather (use gently) the throttle when pulling away in heavy traffic or backing out of my garage for example this makes it easy to stall. I can "drive around" this but it seems wrong to me. It is the same with sport button on or off. Have tried the TPS reset using key. No difference.

BMW had the car today and drove it for an hour said absolutely nothing wrong with it - they must have taken a reasonably good dig around because they said the spark plugs were not the OEM spec plugs and do I want them changed. I said no but they still have the car until tomorrow afternoon as they are quoting for detailing work. I did question why they needed to drive it for an hour - given the problem as far as I sense it is evident at idle even if you stand outside the car and stick your foot in and stab the throttle!

So at this point I am a little stumped. Is it because I just don't know the car (had it 3 weeks only), or because the reception guy told the tech guy who told another guy and the symptom wasn't explained properly, or maybe it is the non-OEM plugs!

Any opinions on this? I am planning to go up to there tomorrow during the day and try and SHOW the tech guy the problem personally - something they said "isn't necessary" when I dropped it off this morning ...

TIA
Sam.
 
It's definitely not in your head Sam, mine used to do it and it was really really annoying. There are tons of threads around here and on the us forums about it, which no doubt you've read. I haven't seen a conclusive answer from any of them sadly.
Weirdly whilst everything points to some kind of sensor/icv/actuator etc issue mine was fixed randomly by taking the engine out and putting a new head gasket/cams/rod bearings, everything else remained the same. All been good for 25k+ miles Go figure :?
 
I personally think it's the idle control valve that causes most of these problems. Cleaning mine helped for a while.
 
If I were you I would demonstrate the issue to the dealer yourself. I always do this now otherwise they say say "Nothing wrong with it sir" unless the issue is obvious.
 
TomK said:
It's definitely not in your head Sam, mine used to do it and it was really really annoying. There are tons of threads around here and on the us forums about it, which no doubt you've read. I haven't seen a conclusive answer from any of them sadly.
Weirdly whilst everything points to some kind of sensor/icv/actuator etc issue mine was fixed randomly by taking the engine out and putting a new head gasket/cams/rod bearings, everything else remained the same. All been good for 25k+ miles Go figure :?
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Okay I'll them to do that then!!! :D

Seriously though I do find it annoying - no codes so nothing definite to go after. And as you rightly say (having trawled through everything I can find about similar issues on this model and other BMW's even other cars) the whole list of what it might be is the same! Its fairly easy to "drive around" it but its already annoying me after a few weeks so I would like to get it fixed. I might go down the road at this point of cleaning stuff like ICV as others have suggested but I find it crazy that a main dealer won't know to do that themselves. They actually told me (and no joke) that I need to drive it harder as its an M car as if I had just graduated from Seat Ibiza 1.9tdi - completely ignoring the fact that once its rolling along it droves fine, the problem is getting it moving without giving it loads of pre-clutch throttle!! I am determined to go back tomorrow whilst they still have it and show them this is not normal - find a solution. See what happens then ....!! :fuelfire:
 
Lower said:
I personally think it's the idle control valve that causes most of these problems. Cleaning mine helped for a while.
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Thanks - I did tell them in my initial email and today on the visit that it was my suspicion too - the problem is they just kind of look at you like you have 2 heads and say no problem, we'll know what it is. Did you have the exact same issues? Did it cure them permanently or just for a while?
 
srhutch said:
If I were you I would demonstrate the issue to the dealer yourself. I always do this now otherwise they say say "Nothing wrong with it sir" unless the issue is obvious.
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Fully agree with you - I am going to do exactly that tomorrow. I will update with the outcome!
 
Mine had the same problem, couldn't find the fault.
When the service was due and sparks replaced, it went away :thumbsup:
As mentioned before, it seems to be caused by different things for different cars.
I'd start with cleaning the ICV and doing normal (relatively cheap) service items so that the car benefits whether or not the issue is resolved.
 
NavZ said:
Mine had the same problem, couldn't find the fault.
When the service was due and sparks replaced, it went away :thumbsup:
As mentioned before, it seems to be caused by different things for different cars.
I'd start with cleaning the ICV and doing normal (relatively cheap) service items so that the car benefits whether or not the issue is resolved.
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Thanks for that - on that basis given the car is still there would you advocate them changing the sparks for OEM ones in place of those they have identified as non-OEM? Probably clutching at straws a bit here I know.

Taking away the fact thats it an M car etc. for a moment and just thinking of it as any car with an engine, it would seem a rev drop on hitting the throttle must be either a very short lean condition where there is too much air or too little fuel. How does the ICV actually interact with the main throttle bodies? Thats a big gap in my knowledge.
 
I don't have much knowledge regarding the different sparks but it couldn't hurt to post the exact specs of your current set.
I'm sure someone here will comment whether or not they're appropriate.
While it might not be the culprit it could potentially lead to other problems or a loss in power, you never know.
 
When I had this I changed both Throttle Postions Sensors (tps) and had the idle valve cleaned. Solved it for me but recently it started to creep back... had a go at the idle control valve last weekend and so far it seems better.

Does yours take a long to fire up from cold start? That what pointed me back to the idle valve reading various forums on the S54 engine.
 
Adam D said:
When I had this I changed both Throttle Postions Sensors (tps) and had the idle valve cleaned. Solved it for me but recently it started to creep back... had a go at the idle control valve last weekend and so far it seems better.

Does yours take a long to fire up from cold start? That what pointed me back to the idle valve reading various forums on the S54 engine.
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Hi Adam

Thanks - no it fires up first turn of the key from cold. Any got a link which explains on BMW how idle control valve works and interacts with throttle? I'd like to learn more about it all works in the hope of thinking through the problem more!

Thanks
Sam.
 
Evening all

I went back to BMW today with a mate of mine. Said to the garage guy there that I wanted to show him the problem. He looked pretty annoyed actually - insisting it was perfectly okay and he had personally driven it for an hour and there is nothing wrong with it - that you have to drive them hard etc. Told him to start it up - so he gets in, revs it, blips throttle: fine he says. So we said, no wait 5 minutes for it to heat up and revs to settle lower. He's getting annoyed now for sure. So with it warm I said okay hit the gas now and sure enough, revs dropped before picking up. Little stabs at the throttle induced momentary stuttering - so I said: okay you think thats normal then? Ok no sir we'll have another look ....

Sorry NavZ no idea what plugs are in it at the moment - but I have told them to change those anyway.

On the plus point they gave me a fantastic price on the detailing I wanted them to do!

All the best
Sam.
 
Dealers don't like bring challenged do they.

Mine know what I'm like now so as long as I deal with somebody I know I get decent service.
 
srhutch said:
Dealers don't like bring challenged do they.

Mine know what I'm like now so as long as I deal with somebody I know I get decent service.
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They'll get used to me! Its got its own parking space inside their workshop now!!

But seriously I am spending hours now reading up on diagnostics and how air intake temp, MAF, O2, TPS, ICV etc. all can be tested - as someone else answered me already on my question about TPS testing using live-data its probably outside of the ability of the kit I have, but these people MUST surely have the ability to test all these components and figure out which one is not giving precisely the right data? My mate summed it up quite well when we looked around the parking lot - loads of cars in for service, brake swaps, plug-it-in-and-change it type repairs - why would they really bother with mine?! Easier just to fob me off. Well lets see what happens next - I suspect what will happen is they will change the plugs, do the detailing work and tell me there's nothing else wrong with it.

So time for a plan B i think.
 
Do BMW actually do detailing work that's beyond wiping it over with a gritty chamois?! :o Never heard of them being used to detail, do they actually have machine polishing equipment?!
 
AndyBeech said:
Do BMW actually do detailing work that's beyond wiping it over with a gritty chamois?! :o Never heard of them being used to detail, do they actually have machine polishing equipment?!
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:D know what you mean!! Was watching a guy slopping suds all over someone car with a broom today!!

This one has a BMW bodyshop who do insurance repairs separate from the main garage

My car has what look like something has sprayed on it on one half of the bonnet and wing, run off and then slightly eaten into the paint. You can only see it under sunlight if you move to the right angle but since rest of the car is immaculate I wanted to get this done. Tried tiny area with a bit of T cut but didn't shift it and although I have a polisher I didn't fancy risking it!
 
Very frustrating to get techs, dealers , service desk personel or any one else to Listen to what you are saying, often the desk staff , m or f ,know nothing of mechanics or tech stuff so relay totally misunderstood info to the service guy. Who again only wants to do brake pad changes or inspections that are robotic and he doesnt need to think out of the box, the hour test is really an excuse to get out of the garage for an hour, go for a cruise in a m car , probably rag your pride and joy whilst he is at it and then brings it back and says nothing wrong mate. Had this recently on one of my vans for a warranty issue, they sent a valeter out for an hour to see if the lights cam on ! Ffs! I bet they billed renault for a tech tho, same scenario. Nothing wrong mate , and they didnt tell me the twat backed into something and smashed my rear light!💥😤 hope you get it sorted mate 👍
 
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