Juddering when accelerator slightly in use....

[Speedtouch]

I think you get a free K&N air filter thrown in FOC though!

[daimlerman]

Yes,but I already have one...and a zone chip to suit the 2.7....

[Speedtouch]

Buy another E30 then!

[march109]

tbh I find it absolutly amazing so many of us have had this porblem and its not a small problem either and noone can solve it, I had another go this avo and I'm buggered if anything I do will fix it.

[Chris]

Mines got this too, or at least i think its the same thing.

My dad was told many years ago that it a very slight imbalance somewhere, he new that was crap but as it hasnt got any worse in 15 years i dont think he worried much.
Would be nice to sort it out though

[funkyjoe]

Reading through this lot, and combined with waht i have done to my 320i, I reckon the problem could be either calibration of the AFM or even unstable metering of the AFM at low revs. I agree that it gets worse as the engine warms, but assume that is due to the initial rich fuel at startup switching to normal running.
If the AFM flap is unstable at low revs, I assume that would cause the ECu to turn the injectors on and off a bit. Which is what is feels like. Its a positive feedback problem for sure. I have replaced every component between the air filter and the exhaust manifold, including the head, but not the inlet manifold, so not much left really. i plan to borrow an AFM off a car that has no problem, maybe the ECU too. If that fixes it, we got a resul;t, will take a while though so feel free to try it yourself and let us know if it works.

[k]

Having owned a few cars in my time, this type of problem has happened on more than one occasion. Unable to drive slowly in town without lerching, always ready to dump the clutch and get control etc.
I don't pretend to have the in depth knowledge of some of you, but my problems have usually been that the mixture setting on the AFM being wrong.
In the early days of carb cars you used to listen to the carb and exhaust note and eventually convince yourself that this was the correct setting, followed by a road test and more adjustments then road test etc..
Once FI arrived and the the little allen screw down the hole on the AFM you can't do this without the proper garage CO meters etc. I would check for any air leaks/ knackered pipes on the system which can cause this poblem first, then get the mixture on an emissions tester/MOT type machine and set it as per Spec. Get them to check before they start twiddling the screw so you know what the initial reading was, then adjust to get it correct, but always remove the allen key and blip the throttle then let it tickover before finally agreeing it's set OK .
My Sport is just just on the edge of doing this and it's only done 73K and I think it's running a bit rich, so once a few other jobs are out of the way it will be down to the Garage mate who will tweak it and hopefully fix it.

[Speedtouch]

Could be down to a factor of using a digital (Motronic) control system; far from being perfect like they're cracked up to be, all such systems seem to screw up one way or another with various glitches - e.g. computer crashes, spurious picture break-up on satellite TV, skipping CDs, etc, etc. It seems they're easily upset and unable to cope with anything less than ideal input signals - which in the real world like in the harsh environment under the bonnet you're never going to get.

At least the Bimmer is better than a '95 Cavalier CDX with 2.0i Ecotec running Siemens 56.1 management which I briefly owned; it would completely cut the engine dead at the most inopportune moments - invariably while going around fast bends, over hump-backed bridges, etc. Fortunately, its head gasket blew giving me a good excuse to get back to BMW E30s

[funkyjoe]

cheers k, that makes sencse. I removed a set of very coked plugs recently. i used to do 2002's on carbs abd still tune by ear and feel. Will take it to a mate with a nmachine, done all the hoses etc

[liam012]

i have all but eliminated my dose of this by would you believe setting the CO to 1.4 instead of the 0.5 i had it at.
It has made a huge difference to part throttle driving,
There is still a bit of lean/surge/juddering very close to either side of on/off throttle but i blame the worn tracks on an old AFM.

[casper8r]

Riight.... I just bought a 320 Touring and at first I thought it was my driving, but this morning I definitely noticed it's the car - about 1500 RPM in in any gear except 5th and it judders. Annoying to say the least. After reading trough this thread I'm feeling a little uneasy - so no definite solution then? Needless to say the acronyms also don't help as I don't know my AFM's from my ECU's.

[liam012]

ECU is the cars main control computer (above your knees under dash panel)
AFM is the Air Flow Meter the unit bolted into the the airbox before and attached to the inlet boot
TPS is the throttle position sensor (under throttle body - cant rreally see unless take intake boot out)
ICV is the idle control valve and is a T or L shaped valve connecting from the thottle body to the intake boot bybassing the butterfly of the throttle body
FPR is the fuel pressure regulater - round canister shaped thing at the end of the fuel rail has a vacuum line connecting to the back of the inlet manifold and a fuel in and fuel out.
strange for you your juddering dissapears at 5th gear, mine was alwasy worst going up the gears to 5 and i could eliminate it by running the car in a lower gear but revving it harder.
interesting...

[Speedtouch]

Sounds to me like as it ages, the AFM, essentially being a rheostat/potentiometer, is behaving much like worn volume controls on old radios/tellys etc. where you get a load of crackle/noise while adjusting the volume - dust and dirt gets into the carbon track causing unpredictable contact with the wiper.

If you were to put an oscilloscope on the output of the AFM (while feeding a voltage into it) you would be able to see this noise. The poor old ECU, expecting to see a cleanly varying signal, can't make sense of it!

Cleaning of the carbon track with electrical contact cleaner and adjustment of the wiper might help.

[casper8r]

Thanks for the rundown liam012. Actually the reason mine's good at 5th is that I would use it on motorway and shift to 5th after reaching about 3-4k rpm in 4th, so this doesn't really mean anything, don't want to put you on a wrong track. I'm pretty sure were I to run it around 1500 rpm in 5th I'd get the same problem... and I can get it to disappear if I keep it in lower gear with higher revs.

Hmm... A bit disappointed by this, I'm starting to think that my purchase somehow corresponds to your signature:
good'n'cheap = not fast
cheap'n'fast = not good
good'n'fast = not cheap

If I can't get this sorted in next couple of weeks I'll just get an MOT and tax on the car and eBay it. So much for cheap BMW dream. I bought it to drive it, I'm not going to spend every (in fact - any) afternoon under it with a spanner. Computers I can do, cars I have to leave to someone else. If this thing requires as much maintenance as I'm starting to believe it might I'd be better off buying one of those FWD Japmobiles, not much Freude am Fahren but at least it stays on the road longer

[liam012]

well pop the black lid of the top of the AFM and you will see yourself the condition of the wiper in there - to be honest, it "could" be a quick simple fix, bit of electrical spray and gentle persuasion of te wiper arm so it makes good contact and you might be happy as larry as they say, DO NOT forget to seal the black lid up with a lick of silicon when you are done as you wouldnt want water in there on top of everything else.
Japanese cars will have problems too i'm sure
or we'd all be driving them.....
wouldn't we?

[casper8r]

Japanese cars will have problems too i'm sure
or we'd all be driving them.....
wouldn't we?

good point!

Found this pic on the web - it's not the same AFM but should be similar enough, is the black plasticky thingy the one I'm supposed to clean? Even though I'm about as technically adept as a drunk gorilla wearing boxing gloves, I'll give it a try.
http://www.davelength.net/car/compare3.html

[liam012]

embarrassingly enough i havent got round to opening mine yet but if you see the left image the coper arm is making contact with the semi circle track - over time crap builds up between the contact arm and track AND the track gets worn away - i am guessing you could "slightly" bend the arm so it makes contact with an unworn part of a track but you would have to bend it on the radius if you know waht i mean? you dont wat to bend that arm left or right just bak or forward a bit either directly towards or away from the centre point.
someone with experience will confirm i am sure.

[Speedtouch]

Sounds like you're on the right 'track' there

I wouldn't mind betting that putting a suppressor choke (such as that usually fitted in the power lead connection to car stereos) in line with the output from the AFM would help immensely, to filter out unwanted noise from reaching the ECU.

[casper8r]

I tried taking the plastic cover off but there doesn't seem to be any other way of removing it apart from prying it off by brute force. Thought I'd ask before doing that though as plastic on old car can become brittle with age, wouldn't want to break it off! It seems to be sitting on tightly though. Anything I need to know before I "break" it open?

[DaveD]

btw the left one is from a 535 the one on the right is the 325

[Ant]

Most of the part throttle shunting is down to a badly adjusted TPS.

@ low openings it is possible that the ECU will see the idle switch from the TPS as the throttle is modulated on a long run.

the TPS must be open circuit as soon the the throttle moves from its stop, not a few degrees after, a new throttle cable is always £Â£ well spent too, as they stretch to buggery

With regards to the AFM, easiest way to pop the lid is a blunt butter knife, use the alloy casing as a pivot and rock the blade under the lip both sides and it will come free without any damage.

look for cloudy screen printing on the PCB inside, a sure sign that moisture has go into the unit.
Check the wire from the arm too, have seen a few that had gone brittle with old age cauising weird running at extreme limits of travel.

Assuming the PCB is ok, you can move the arm to a new position by sliding it up or down on the shaft a mm or two and tweaking the bends very gently, you want good contact but little pressure otherwise that carbon track will wear very rapidly.

Dont forget to clean the air temp sensor too, often clogged with oil and worse than useless.

Important point to remember , the AFM works only on 2/3rd of the effective throttle range, the TPS does the idle, and WOT , the AFM signal is ignored by the ECU once the TPS is closed circuit either way, check those switches 1st gents !

HTH

[liam012]

cheers Ant , how best to clean the IAT sensor in the AFM though? its only a wire so hard to scrub or get the dremel to
just spray it with electrical spray?

[Ant]

carb cleaner( or brake) Liam, its an open element NTC resistor so anything on the surface will affect its operation, common when used with an oil based filter media as per K+N etc.

[liam012]

mmm, my ITG was exceptionally "lubed" when i got it.....
i wonder has it pooped all over the IAT... will check it out
thanks Ant

[casper8r]

Was very surprised when opened the AFM thingy - it looked brand new! It was either never opened (the sealant may have well been there from factory) or exchanged at some point. Gave it a thorough cleaning with one of the electrical contact cleaners that I borrowed from our workshop (used for repairing electronic equipment). I also noticed that the PCB next to the track has tiny incision-like stripes which looked a bit affected so I cleaned them too. Yeah, I know it sounds like an OAP explaining something to a computer repair person

Anyway, it seems to be better at the moment, I've been able to slowly accelerate in 2nd, 3rd, 4th and 5th from about 1000 rpm ok, but it felt like it's still there, only much weaker. Will get back tomorrow after sitting in a few traffic jams (gotta love those M1 roadworks!).

[smithy318i]

Before anyone starts pulling covers off the AFM, you should test it 1st.

The way to check an AFM is to put a 6 volt battery across pins 4 and 3, and then connect an analogue voltmeter across pins 4 and 2. As you open the flap, the voltage on the meter should rise smoothly with no jerks or "drop outs".

[Brianmoooore]

If I can't get this sorted in next couple of weeks I'll just get an MOT and tax on the car and eBay it. So much for cheap BMW dream. :

E30s are a victim of their own high quality engineering, in that they go on and on after a fashion with little maintenance.
When you buy an E30, which is likely to be 15+ years old at least, and with mileages that would see most manufacturers' engines little more than scrap, you almost always find a collection of minor issues that need to be sorted.
Once all these issues have been addressed, usually at little cost, then you will end up with a car that is one of the most reliable on the road; the equal or better of most new cars as well, and will still be, when these new cars reach the scrap heap.

[Brianmoooore]

I'm determined to get to the bottom of this 'kangaroo' issue, and to that end, I've invested in a 4 gas exhaust analyser today. Only problem is lack of time, but I will get there!

[casper8r]

Thanks, Brian. Because I'm technically challenged (or rather ignorant and impatient) I can't contribute much to this thread, but this issue is puzzling and I'm sure I'm not the only one who would be happy to see it resolved. A from me to whoever gets to the bottom of this, preferably somewhere in 30 mile radius to Luton

At the moment the AFM route seems to be dead end because the issue isn't gone, it's still present and as somebody noticed it gets worse when engine is warm. Maybe I should have adjusted the arm on the AFM to slide over different path, I'll try to do that tomorrow, but that would be too easy, wouldn't it

As for the e30 build quality - mine is 17 years old, I've only had it for few days and a good one at that (thanks to Spadge), but it seems to be built to last, and properly cared for should last for some time. That being said I'm already starting to contemplate some mods. Must... stop... have... other... priorities... must resist...

[liam012]

does anyone else have warm starting issues as well as the kangarooing at low revs?
just curios
there is a valve in the fpr i read in the bently it is there to help warm start - i must dig out the relevant section -
also if the probem gets worse with heat could one presume its to do with something expanding?
and doesnt a diaphgram expand and what not? and isnt that basicly what the fpr is?
just thinking out louud.....

[Jonny_71]

Hmmm, I'll certainly be checking out my AFM tomorrow but it might just be relevant that my cars juddering only started after it'd been off the road for a couple of weeks due to it not being able to start. This was eventually traced back to a knackered immobiliser but in the search for a remedy I replaced the FPR and also the crankshaft position sensor. I've still got the old parts that I replaced so I'll also be swapping them back to see if the juddering disappears. Watch this space........

[smithy318i]

does anyone else have warm starting issues as well as the kangarooing at low revs?
just curios
there is a valve in the fpr i read in the bently it is there to help warm start - i must dig out the relevant section -
also if the probem gets worse with heat could one presume its to do with something expanding?
and doesnt a diaphgram expand and what not? and isnt that basicly what the fpr is?
just thinking out louud.....

Mine doesnt seem to care what temperature the engine is at. I have been testing it this morning when the engine was stone cold, and hey presto, 20mph+1500rpm = boing boing boing.

[Speedtouch]

So you can do good impersonations of your Avatar, Smithy?

[casper8r]

So, anyone have any luck with adjusting/swapping their AFM's? It would be great to at least eliminate/confirm this suspect. If it's indeed the AFM might have to go the whole Miller MAF conversion route. Anyone know of any nearby banks with lax security?

[Jonny_71]

Cleaning the guts of the AFM has certainly improved the situation on my car, but the juddering is still there, just not as bad as it was previously.