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Topic: E30 low rpm poor throttle response Posted: 06-December-2004 at 03:55 |
I'm beginning to suspect all is not quite what it should be with my newly aquired E30 M3.
I had reserved judgement until I got the awful Scorpion exhaust system
and Green cone air filter off in case that was clouding things, but now
I have put the original BMW airbox back on and a nice quiet new
Supersprint exhaust system (with the crucial x-pipe).
The throttle response is very tardy at low rpm, approx the first 2000
rpm. If you blip the throttle in neautral at those engine speeds it
bogs before it revs. At higher rpm it's fine.
I cleaned off all the crud (and there was a lot of it) from the
distributor cap and rotor contacts yesterday but no difference. I have
a new distributor cap and rotor arm coming this week anyway, and
replacement Magnecor HT leads are also on their way.
Any theories what might be causing this issue? I've not noticed
it missing at all, just being very tardy to rev at low rpm.
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Nick
Bavarian-Board Contributor
BMWCC Area Organiser Yorks & Humber
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Location: God’s own county... Yorkshire
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Posted: 06-December-2004 at 04:07 |
They all do that sir..
..sounds like fouled plugs, very common... as are the dizzy and leads, but you are on with those.
It will never have the low down urge of say a 325, but you will soon get used to it.
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Posted: 06-December-2004 at 04:13 |
I had the plugs out last weekend and they looked ok. If thats how
they all are then fair enough, I was just expecting to be able to blip
the throttle and the engine respond immediately.
I guess the masters in Zuffenhausen have spoiled me...
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PJSM3
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Posted: 06-December-2004 at 05:23 |
Tim doesn't sound right to me. These cars have quite a 'power band' but should still feel pretty strong at low revs. I had a similar severe flat spot below 3500 RPM on my E30 M3 that was sorted out for me by Moseley Motors. It was something to do with adjusting metering of air (sorry can't remember the details). It transformed the car. Didn't need any replacement parts. Have a word with Nigel at Moseleys or someone who is familiar with these cars.
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Nick
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Posted: 06-December-2004 at 05:42 |
_Tim_ wrote:
I guess the masters in Zuffenhausen have spoiled me...
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Please read the forum guidelines about posting offensive remarks.
Seriously though, without driving your car it is hard to diagnose the fault.. if it is more than just being 'off cam' then you need it sorting. These cars will never have the grunt of a porker but will outshine them in all of the other driving disciplines.
Air flow meters (AFM) can be problematic, but lets get those leads and dizzy bits changed first and then report back.
Zuffenhausen indeed!
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Posted: 06-December-2004 at 06:00 |
LOL, I thought that would yank someones chain! :p
I know the difference between low torque (I've owned a Lotus Elise) and odd running. This definately feels odd to me.
Whilst refitting the AFM to the airbox I noticed that the flap inside
felt like it was sticking slightly as it moved. From memory, at
the engine side, it has about a centimetre of movement before the flap
closes the gap - at that point it's definately not a smooth movement.
Is there any manual adjustment on these things, or is it all via the ECU programming?
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jon90
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Posted: 06-December-2004 at 06:14 |
Tim.
Bogs down or slow to react.If its slow to react I`m affraid it is a trait of these cars,due to the afm setup.The barn door is very slow to react and that`s the main reason people dump them,a custom remap works wonders and is well worth considering.
Jon
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Nick
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Posted: 06-December-2004 at 06:21 |
_Tim_ wrote:
LOL, I thought that would yank someones chain! :p
(I've owned a Lotus Elise)
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.. who's laughing now !
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lancelotII
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Posted: 06-December-2004 at 06:27 |
I thinbk if the AFM is a bit tired you may get this. In addition if it's running a tad rich it will also do it. The most noticeable thing after a remap is that they are much brighter at low rpm especially just after start up, where they normally really chug until warmed up. They are by default very rich at start up hencr the chugging and ease with which the plugs can be fouled. A remap will sort all that, but that's once you know all the other bits are healthy.
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Posted: 06-December-2004 at 06:31 |
Interesting, thanks guys.
Since I'm replacing plugs, ht leads, distributor cap and rotor arm, I'm
thinking I might do the coil as well and then I'll know the whole
ignition system is good.
Is a new AFM expensive? I'm guessing it's a trousers down job from BMW.
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215DMX
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Posted: 06-December-2004 at 06:36 |
Might be worth trying swopping over the afm/ airbox
with a know working example. Otherwise it could be
that it needs setting up properly. i.e. setting base
idle, synching the throttle bodies, setting the CO, etc
Also worth checking for air leaks around the seal on
the afm if you have just re-fitted it + the usual
suspects.
worth a read:
(u will have to paste manually as 'LINK' dosent work
for me, sorry)
http://member.rivernet.com.au/btaylor/BMWText/techn
ical/AirflowMeterCalibrat.html
Edited by 215DMX
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UweM3
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Posted: 06-December-2004 at 09:07 |
lancelotII wrote:
...especially just after start up, where they normally really chug until warmed up.... |
Mine always felt the opposite. Very crisp and responsive when cold and after a few miles you could really "feel" some sort of switching to a more sluggish response. I have tried to investigate in this matter to see if maybe a different ignition map is used for cold running but nobody seemed to be able to understand the Motronic good enough to tell. Or nobody really wanted to tell me........
Edited by UweM3
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E61 520d, slow and buzzy but my wallet likes the mpg.....
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lancelotII
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Posted: 06-December-2004 at 10:36 |
Mine used to chug before it was remapped, now it's much better.
Roops
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geo
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Posted: 06-December-2004 at 10:51 |
_Tim_ wrote:
Is there any manual adjustment on these things, or is it all via the ECU programming?
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There is manual adjustment on the AFM. I know because there is evidence that the black plastic cover on mine was taken off and underneath it theres a dial with numbers on it and a needle that can be moved around to adjust it. There's also a note on one of the service invoices from ML saying the AFM was adjusted.
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No BMWs in the family (for the moment) Other stuff includes Mk2 Golf GTI 8V and G60, Vento VR6 track car and a few other bits and pieces
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UweM3
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Posted: 06-December-2004 at 11:30 |
If the spring becomes a bit worn some people fiddle around with the pre-tension of the spring(under the black plastic cover) but I've been told to keep hands away if you don't know for sure what you'r doing.
Best option is still to delete the AFM. I have spend a fortune for a new 2.5 engine with hot cams and still drive around with an 17 year old AFM. That can't be the best solution.....
Edited by UweM3
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E61 520d, slow and buzzy but my wallet likes the mpg.....
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lancelotII
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Posted: 06-December-2004 at 11:41 |
Ahh yes the spring. It is not uncommon for peoople to tamper with this, their thinking being that make it richer to get more power. err no, no no and thrice no. This really needs to be done by someone who knows what they are doing, preferably with a gas analyzer hooked up.
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Houlbt
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Posted: 06-December-2004 at 12:11 |
Well if it is the AFM mine is coming off my car as we speak so i am sure you could persuade me to part with it for a small donation...
Speak to Bexleys in Kent if I were you, get the car remapped and if it is the AFM they can shove mine on there and then
Tom H
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Posted: 06-December-2004 at 13:21 |
Houlbt wrote:
Well if it is the AFM mine is coming off my car as we speak so i am sure you could persuade me to part with it for a small donation... |
How much would you be looking for it? I've got a session booked with a local tuner/FI specialist on Saturday morning so if it turns out the AFM is fubar then I could well be interested.
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