running problem number 2 ***HELP!!!***

[Toby_Unna]

right have done a u-turn and i'm now taking the 335i to lemans this coming week.

so please help me solve this intermittant running problem i can't seem to fix, by Thursday! before I go crazy and torch the thing half way through France! it's an m30 3.5 (e34 535i) but similar to most other bmw engines.

basically half the time it runs fine. then suddenly it won't take much throttle without coughing/hesitating/missing. it will still run fine at light throttle and will rev ok off-load.

sometimes the problem just stops it from pulling cleanly through the rev range and gives poor throttle response, sometimes it's so bad that it won't do more than about 50mph (i.e. light throttle in top gear)

it can start running badly at any time while driving, but never cures itself quickly. it always fixes itself after a while, usually after being left for a day or two, but sometimes just get in it next morning and it's fine again never fails to start quickly and never actually cuts out.

thing's i've looked at already:

fuel:
changed fuel pressure regulator
checked voltage at fuel pump when it's running
fuel filter is near new
tank is brimmed
no obvious fuel leaks or fuel smell


electrics
changed alternator
changed battery
changed coil
changed AFM
checked TPS
changed coolant temp sensor
changed ECU
changed rotor cap/leads/plugs are near new
checked earths
changed ICV

the problem appears and disappears quickly, don't think injectors can be blocked? do fuel pumps ever fail gradually/intermittantly like this? haven't checked the crank position sensor but surely if it was bad the car wouldn't run at all? i have run the coil and fuel pump on direct,permanent live feeds from the battery and it didn't make any difference. no obvious air leaks.

ANY INPUT appreciated, even if it just points me towards fuel or electrics?

if someone finds the problem for me there'll be a few drinks in it!!!

[Geeman]

It'll be the mis-match'd coloured body kit that's causing it. Take the kit off and see if it runs properly. If not, try spraying the bits the same colour as the car... that should cure it.

Hope this helps...

Ever useful...

Giles.

[tylerma]

hiya mate
probably wont be of any help
but i do try

i know these engines are fuel injected and not carb
but do they have any sort of automatic choke system on them
(possibly part of the electronics)

reason i ask is my old man has a e34 530i
and if i try and give that a bit too much throttle too soon after starting up
it seems to bog down
(if you get what i mean)

basically where i am going with this is

do you have an automatic choke that is sticking open
or cutting in when it shouldnt

or could it be a sticky butterfly on the throttle body

like i said i probably wont be of any help
or could be talking sh1t
should i get me coat

[Toby_Unna]

nothing like a good laugh to help with a problem like this, cheers Giles!

i'm hoping to spray it tomorrow evening, fingers crossed this will fix it. it also occured to me that i haven't driven it since i fillered the crack in the rear valance this afternoon, maybe that's already cured it.

[Toby_Unna]

hiya mate
probably wont be of any help
but i do try

i know these engines are fuel injected and not carb
but do they have any sort of automatic choke system on them
(possibly part of the electronics)

reason i ask is my old man has a e34 530i
and if i try and give that a bit too much throttle too soon after starting up
it seems to bog down
(if you get what i mean)

basically where i am going with this is

do you have an automatic choke that is sticking open
or cutting in when it shouldnt

or could it be a sticky butterfly on the throttle body

like i said i probably wont be of any help
or could be talking sh1t
should i get me coat

all help appreciated! it could be intermittantly running rich i guess, it's certainly using enough fuel to justify that answer

[Ant]

Have you tried replacing the DME and/or fuel pump relays dude ?

a good plan would be to conti test allthe loom back to the ECU connector, could be as simple as a broken wire that makes contact when cold but cant jump the gap once the engine is up to temp and the insulation softens

[tylerma]

I hope you get it sorted mate

[pete325i]

I had a problem where the engine cut at high revs, just for a second. Took me two weeks to work out it was the Crank Sensor, it ran normally most the time but cut when you gave it some "beans".
I thought the crank sensor would either work or not work, but when the crank is going faster it's harder for the sensor to read.
Borrow one off some one and test it, at least you've ruled it out then.

It may not be this but I hope that helps

Pete

ps I think the M30 Crank Sensor is the same as the M20 ones.

[Geeman]

Aaaaah, you didn't say you had a crack in the rear valance. If you've filled that, that's the problem solved then.

[Martinaston]

You have the same symptoms as the M40 engine when the ECU temperature sender goes up the spout.

[pete325i]

Also your engine may have two sensors in the bell housing to feed back position and speed, I think. May be worth checking those out.

Going back to the crank sensor, I did loads of checks on my faulty one with a multimeter and it seemed fine, ........but it wasn't.

To be honest it's probably the paintwork, have you tried changing the windscreen wipers?

Pete

[Geeman]

Or turning the headlights on... I find this cures 95% of my running problems...

[TOURINGDADDY]

Just bang it

[Andy335Touring]

Also your engine may have two sensors in the bell housing to feed back position and speed, I think. May be worth checking those out.

Pete

Toby has the latter Motronic set up from the E34/2 that just has the one crank sensor at the front.The older set up from the E28/4 didn't have the front sensor it had two in the gear box bell housing that was triggered by marks on the edge of the fly wheel.

Toby if you want you can try my CPS if you want ?

I can give you a hand to test your loom when i come over if you've not all ready done it ?

[ian332isport]

Have you considered water in the tank (as in you may have some) ?

I picked up a dodgy tank of fuel a while back, and it was just like your description above.

After sticking a couple of bottles of stuff in the tank that causes the water to mix with the fuel, it was fine.

It certainly sounds like a fuel problem to me.

Cheers,

Ian.

[Brianmoooore]

It does sound like an ignition fault, but you seem to have tried most things.
Take up the offer of the CPS, it's definitely a possibility.
Only other electrical things I can think of, are 1/ the ignition switch. (The next time it acts up, check if the reverse lights work at full brightness)
2/ A poor connection at the C101 connector, pin 7.

[Martinaston]

Just had a look on oem that thermostat housing has three temperature sensors

[Brianmoooore]

M20 thermostat housing has two sensors, brown and blue and a blanking plug.
Ian323isport's water in fuel idea is well worth checking out as well.
There's a drain plug on the offside of the fuel tank.
Clean out the hex socket in the plug and make sure your hex driver is fully in before you try to unscrew it.

[Toby_Unna]

some excellent ideas here, hugely appreciated!

water in the tank sounds possible, i guess water's denser than petrol so would sit at the bottom and get continually sucked into the system. any idea what the stuff is called Ian (i've never heard of such a product)

CPS also sounds possible Pete, like you i ruled it out on the assumption that it woudl either work perfectly or not at all.

Brian i don't think the ign switch or c101 are the problem. i thought this same thing so i wired a tick wire directly from the battery to the coil's power-on positive terminal, this made the ignition come on without the key in the barrel and it ran no better.

Temp sensor's already checked but as Ant said it might be the loom

fantastic response anyway will post when (NOT IF) i get it sorted. bought the ferry ticket from a mate now, it's Le Mans or bust

[Toby_Unna]

ps, i haven't exactly got around to wiring in reverse lights yet

it's on the list

yanks say the same thing, water in fuel or failing CPS, good calls both i think

Andy cheers for the offer i'll mail ya tomorrow when i've talked to sytner and ECP about the oil pump bits and sump gasket, when i do it depends on when they get the bits.

[Brianmoooore]

If you've fed the coil direct with 12V+, then ignition switch and C101 are not the problem.

[ian332isport]

any idea what the stuff is called Ian (i've never heard of such a product)

I can't remember exactly what one I used, but most motor factors will have something similar.

This sort of thing though:

http://www.wynns.uk.com/contextra/docum ... 20Fuel.pdf

Cheers,

Ian.

[Toby_Unna]

fantastic, thanks for that ian

[randomdave325]

sounds like you may have sorted it. but i'd go with the cranksensor idea. thats what it was on my m20 (similar problem) and took ages to find. it's thesame sensor as m20 and 80's motronic vauxhall ones will work. the only difference is the plug is straight not angled like the bm one but they've got me out of trouble before . if all else fails they're only about Ԛ£18 new. go for a genuine bosch if you can. the g&s ones work just as well but are plastic.
hope this helps

[Toby_Unna]

cheers for that Dave hopefully get it sorted tomorrow. couldn't find the fuel drier stuf in graham goode today but i'm going to drain the tank tomorrow

[Toby_Unna]

looks like ant gets the drinks

one of the leads between AFM and ECU showed 40 ohms resistance, even when the dirty connectors were cut off each end

replaced it with my screen washer pump wire and some plug block and it's run mint for 750 miles

only found this out once at le mans, missed a beat or 2 on the way down so i whipped the multimeter out at the campsite on friday morning. when i was testing the loom it was so hot the LCD on the meter kept going black, 33degrees or something

[Andy335Touring]

Nice one Toby,is your internet connection all sorted ?

[Toby_Unna]

internet fine now

335 not fine, running a bit hot now, probably damaged by le mans!

bit odd, gets hot even with cooling fan on in traffic or at speed, but seems to run at normal temp if cabin heater on, gives nice hot air.

but then when parking today the heater started to run cold. hopefully water pump or something, rad still getting hot so think the thermostat's ok. or blocked rad. no water leaks

or holding it at top revs in top gear has done something terminal to the head, which wouldn't be unreasonable really

have a look tomorrow. still want that manifold!

[Andy335Touring]

Mines been a bit hot,i'm not sure if its the gauge playing up ?

When can you pop over for that manifold mate ?

[Andy335Touring]

Forgot to say i might be going distibutorless soon as i'm hoping to get a coil pack from a cossie Scorpio for 20 notes,just got to hope my ignition leeds have the correct ends on them.

(shit picy from ebay)

[Toby_Unna]

that's quite cool, is it much effort to wire that in instead of the coil?

motronic doesn't use a dizzy as such, just the cap and rotor. but would still be VERY nice to lose the cap, that's the bit that's closest to the rad on mine, you can't remove it without having the rad off

minor cash flow situation after le mans but after a couple of cheques have cleared i'll be waving twenties at you! early next week ok? i take it you had no more joy trying to fit it the other day?

[Andy335Touring]

that's quite cool, is it much effort to wire that in instead of the coil?

I'm guessing it will be 1 x + feed and 3 x switched - from the ECU,the ECU will need some settings changing but i shall have to phone up Emerald to see whats what.It will be a wasted spark set up.

motronic doesn't use a dizzy as such, just the cap and rotor. but would still be VERY nice to lose the cap, that's the bit that's closest to the rad on mine, you can't remove it without having the rad off

I know what you mean,i was struggling for a descriptive word use so i said distributorless.I think my rad would have to come off as well to remove it but i might just leave it on as i can't think what i'd use to blank it off ?

minor cash flow situation after le mans but after a couple of cheques have cleared i'll be waving twenties at you! early next week ok? i take it you had no more joy trying to fit it the other day?

No probs mate.I'm working 12-8 Mon,D/O Tue,12-8 Wed,8-4 Thur/Fri/Sat.

I didn't mess around trying to fit it,i just put it all back together.

My exhaust putty had gone off so i had to use house hold silicone(sp?) sealer on the M3 down pipe/exhaust flange and two days latter it's still not blowing !

So that racer myth is true