Engine STILL occasionally reving up on its own 'FIXED'

[abelai]

I have run carsoft on mine and also read the fault codes via the DME and wiring up an engine check light to pin 15 off the DME loom. The info pretty much only tells you if somethings fallen of the engine. BMW usually charge less for older cars and a diagnoses of the problem might be a flat rate plus if they can't fix it you could probably kick up one hell of a fuss to BMW UK untill they fix it.

[liquid079]

Actually since putting the manifold back on this problem is actually quite a bit worse I must have disturbed something, the question is what.

[abelai]

Maybe you should consider removing the engine loom and checking every wire?

[liquid079]

But I'm still convinced there's an air leak.

Isn't removing the engine loom a huge job?

[Gibson]

ok mine is getting worse... it now does it pretty much all the time on start up then stops for a while. then more again when its warm. maybe its the temp sensor? i know people have tried that on thiers, has any found that is the problem?

[liquid079]

Probably worth replacing the blue temp sensor anyway as its only about a tenner.

I'd take the idle control valve off and give that a good clean out with carb cleaner, as its nice and easy to do.

Dan.

[Gibson]

cheers yea im gonna remove and clean the ICV and the AFM.... someone has stuck a silly cone filter on my car could this be doing something funny too the AFM? it drive fine for at least 2 weeks after i bought it before it started doing this though...
where is ICV and is there anyything i should watch out for when removing it?
it feels so much like a sensor problem tho... is there a cheap way of getting diagnostics run on these cars?

[liquid079]

320iAN I think your aviatar is just a smidgen too big at 680 x 510 pixels, mine is 130 x 173 pixles which seems to fit just fine.

Gibson- The ICV is the little black tubular thing(either L-shaped or T-shaped), that has one end plugging into the throttle body and the other bit goes into the rubber bellow attached to the airflow meter, I'm sure someone can explain that a lot better than me .

There is a three pin plug to disconnect off of the end of it and a little harness clipping onto the bracket on the manifold, then you just wiggle it off.

After this I would try the TPS.

After about three months you might get to the stage I have, where it seems like you have checked everything and still have the fault .

Dan.

[320iAN]

320iAN I think your aviatar is just a smidgen too big at 680 x 510 pixels, mine is 130 x 173 pixles which seems to fit just fine.
Dan.

sorry but i don't know what happened with it? all i knew about it was via a PM from addmin .... i can only think it was something to do with the hosting site that i copied it from ... soz

BACK ON TOPIC ... you may find this strange?
see how about 2 pages ago i thought i'd cured my hunting idle then a few day's later it returned! well i hadn't started my E30 for over a week and yesterday i pulled of the car cover and started it up, no probs as usual, then i thought i'd re-set the service/inspection light's which i did with my Draper re-set tool, started it back up, took it for a short run 3 miles or so and the tick over was faultless, i could even let the clutch hold the car on a hill without the engine stalling ..strange?
sometimes i think my car is in need of a good blast on a long road just to clear some cob web's then day's like yesterday come along and it drives "spot on" smooth and responsive.

[Gibson]

you may find this strange?
see how about 2 pages ago i thought i'd cured my hunting idle then a few day's later it returned! well i hadn't started my E30 for over a week and yesterday i pulled of the car cover and started it up, no probs as usual, then i thought i'd re-set the service/inspection light's which i did with my Draper re-set tool, started it back up, took it for a short run 3 miles or so and the tick over was faultless, i could even let the clutch hold the car on a hill without the engine stalling ..strange?
sometimes i think my car is in need of a good blast on a long road just to clear some cob web's then day's like yesterday come along and it drives "spot on" smooth and responsive.

see this is what leads me into thinking it must be a sensor/ electrical fault. its all too perfect too be an air leak etc the way it will hold at a certain rpm.... and has no power etc... gotta be a sensor giving dicky readings

[liquid079]

320iAN-Mmm thats strange. I think if there is an air leak, the cold weather we are having may cause the seals/gaskets to be less flexible for a while making the problem seem lesser, I might be talking utter rubbish though.

Mine is in the garage now. I went through with the chap the extensive list of things I had done, and he didn't seem to hopefull in finding other things to do.

Two sealing points I didn't really check properly were at the oil dipstick tube(the base), and around the brake servo area, Hopefully they'll get a vacum gauge on her and come up with something interesting... fingers crossed.

Dan.

[liquid079]

Blimey 7 pages

[320iAN]

fingers are crossed for you Dan

[Gibson]

someone has got too have had and remedied this before us lot?

[abelai]

You would have thought so but I've found one hell of alot of information about the m20 engines and motronic 1.3 DME system while trying to find my fault. I have asked BMW in Cardiff (one of the techs there has a 325i sport mint had it for 6 years) and they can't figure out what the hells wrong with my car didn't even know the DME recieved a signal from the clocks VSS but they agree with me that I have a wiring fault somewhere.

[Gibson]

oh man i cant understand all these abbreviations. im only a newbie!
can someone write them out for me?

[liquid079]

Gibson-The Motronic 1.3 DME(Digital Motor Electronics) system, is the engine management system found on most of the 6-cylinder E30's, I think the early ones were fitted with a more basic system just known as Motronic.

VSS-Via speed signal.... maybe

[davidt]

liquid079 - Have you dismantled the multi plug under the inlet manifold, I had some of the issues you are having on my 325i, the lower part of the plug was full of water ,

[abelai]

Sorry for the abbreviations it just takes me all day to type everything DME is also known as ECU and EMC but if you're searching google for stuff you get better results by using DME.
VSS Vehicle Speed Signal
CPS Crank Position Sensor
TPS Throttle Position Sensor
ICV Idle Control Valve (aka ISCV)
AFM Air Flow Meter
MAF Mass Air Flow meter
CTS CoolentTemp sensor

These are the usual ones refered to during this thread. I know this thread isn't the most exciting to read but if you take your time and read it through carefully it would enable you to diagnose and repair all the usual idle problems that an M20 can exhibit.

[Gibson]

i mean i worked most of them out from the context they were being used in. but there were a couple i couldnt. cheers

[Gibson]

ok today is the the day... time too start taking shit apart.....

[liquid079]

Well the garage were due to look at my car today, and since I haven't heard anything from them I presume they haven't found anything, still I'll leave it with them for a few days.

Albelai- you say the BMW garage can't figure out whats wrong with your car, thats worrying , surely the E30 is a doddle to diagnose faults on compared to new cars.

[liquid079]

Davidt-Yea I've checked that connector throughly.

Thanks, Dan.

[evostormm]

I had similar problems on my old M3 (s14). We reckoned in the end it was a faulty water temperature sensor
mis-reading and sending the engine into a cold start cycle (overfueling).

Sorry if this has been mentioned before but I don't have time to read the whole thread.

[abelai]

BMW have not actually had my car in the workshop to diagnose the fault but I have talked to the head tech and they really can't tell me what the problem is other than they agree that it must be a wiring fault as when rolling it gives a perfect idle always and does the same with 2 different DME's.

[Gibson]

thats what i suspect... is the false cold start... so im changing the temp sensor today because it seems too fuck around more when the ambient air temp is colder

[davidt]

As an experiment changed the water temperature sensor for a spare, result was hard to start would not idle until hot and then revs up on its own just the once, also noticed the cut off was instant not gradual like the original, I have now changed it for a new one, its back to normal plus the revs are a bit higher. the tolerances of these sensors seem to vary a lot,

[liquid079]

My temp sensors... in fact all my sensors are under a year old, do you think they could suddenly start misfunctioning at such a young age?

[davidt]

Dan, not sure how temp-sensors work I guess they must act like variable resistors, worth a quick look at just in case it is faulty.

[Gibson]

well i bought blue and brown ones new from bmw so i will tell you how it goes when i fit them! should be sunday

[Gibson]

my new list of suspects are....
Temp Sensor
AFM (i just unclipped it when it was misbehaving and the idle instantly returned too normalish)
air leak around servo area.

[Gibson]

temp sensors fitted... not had the chance too warm it up on a run and test it yet tho... new AFM in the post but im gonna polish that up before i put it on the car...
will silicone spray work for checking for air leaks around the servo area?

[abelai]

It needs to be something flammable, butane/propane gas, wd40, easy start, carb cleaner you get the picture. It will get sucked into the engine and increase the revs or smooth it out but you will here the engine note change if you have a vacuum leak.

[Gibson]

ah ha ok wd40 it is

[liquid079]

Davidt- I suppose I might as well try new ones as they are nice and cheap.

Gibson- Did you buy a BRAND new Air-flow meter, if so how much was it just out of interest?

Cheers, Dan.