bmw 325i auto 1988 engine cutting out!! please Help!!!!

[boston325]

I have a 325i auto convertible on 1988, it cuts out, after 1 minute of starting up, had diagnostics done and picked up the O2 sensor - but the car doesnt have an o2 sensor!!!!??, i've changed the crank position sensor, ignition coil, distributor cap and rotor, before i throw any more money at it, what are your thoughts??

[Brianmoooore]

What EXACTLY does the rev counter do when it cuts out?

[clegy1]

could be idle speed controle valve poss or a split vacume pipe or maf sensor

[boston325]

the rev counter works as normal, idle control is ok too, is MAF the airflow? checked all air pipes and they are good too?

Can it be a faulty ECU?
would air flow sensor cause that problem?

Thanks for your replies

[Brianmoooore]

If the rev counter reads normal, then it can't have 'cut out'! If you don't answer the question accurately, I can't help.
Does it drop to zero instantly or track the engine revs as it dies?

[boston325]

sorry, when i start the car the revs needle is working and around 750-950 rpm, then suddenly the car will switch off and the revs drop back down to zero, when i switch on and i rev the car the needle responds respectively

[boston325]

Sometimes the car will run longer than a minute - the longer i leave it switched off the longer it will run the first time - longer meaning few days, week

[Low_E30]

Blue temp sensor??

[boston325]

I thought of that - thermo time switch - same thing??, but would that cause a problem when the car has reached operating temperature??

[Brianmoooore]

If the rev counter drops instantly to zero, it's an electrical fault!
Crank position sensor is the obvious candidate to be the villain, but you say you've already changed this, so the next suspect in line is the DME relay (white one (usualy) situated under the cover by the air filter/AFM). No need to buy new - a second hand one will do to prove the point.
Another test you can do is to attach a bulb or LED from the ignition coil + terminal to earth, to check if the ignition supply is behaving itself.

[boston325]

yeah the revs drop as the engine dies. its an instant cut out tho, very very occationally it will run for more than a 1minute, about 2 or 3, and cut out again. the longer i leave it the longer it stays on. I kinda know location of most parts on the car, but does these 325's have something called Ingition Amplifier on em?

[boston325]

thanks brian, that is going to be the next thing for me to check tomorrow morning!!! is the relay same as a 318i, as i know someone who's got one, could just try off that

[Brianmoooore]

318i relay is the same, and the ultimate test for any component is to swap it with another car, cure the fault in the original car, and transfer the problem to the other car.

[boston325]

tried tried the relays, but no luck, changed the thermo time switch again no luck, was talking to a bmw breaker and he suggested fuel pump??
can fuel pumps be intermittent?? as in run for 30secs to 1 minute?

[Brianmoooore]

If the rev counter drops instantly to zero, it's an electrical fault!

[boston325]

the revs tracks the engine as it dies, i,ve noticed a funy whistle type noise from near the throttle body as i rev the car

[Brianmoooore]

the revs tracks the engine as it dies, i,ve noticed a funy whistle type noise from near the throttle body as i rev the car

If you'd made this clear when i first asked, nine days ago, this would probably be all sorted by now!
Could well be fuel pump related. Take out the rear seat base, remove the RH inspection cover, connect a 12 volt bulb to the fuel pump connector, and run the car like this. See if the light goes out exactly at the time the engine cuts.
Whistling is probably a perished blanking cap on the unused stub pipe on the inlet manifold just behind the throttle position switch. Half the E30s in the country have this cap all or partly missing, giving idle problems.

[boston325]

thanks brian, this stub pipe, i dont exactly understand which one it is, do i have to remove the throttle body to access it?

[zaust]

Try swapping the dme relay too fella. It's an easy and commonly over looked cause.

[boston325]

thanks zaust , i tried both relays from a running e30, and vica versa, both the relays are working

[boston325]

i removed the throttle body and the stub pipe is as new, next check is the fuel pump, do i need to have the fuel pump connected with the bulb to check or am i just checking current?

[Brianmoooore]

Connect the bulb as well as the pump, so that you can see if the bulb goes out when the engine cuts.

[boston325]

Things I have changed so far -

crankshaft position sensor - new
Ignition coil
Distributor
Rotor arm - new
Cleaned ICV
Cleaned throttle body - stud pipe in as new condition
Thermo time switch - new (brown)
Fuel pump tested - perfect working order
Fuel filter - new
Light bulb test on ignition coil - stays on constant with no flicker

Not yet had chance to check light bulb test on fuel pump - if the result is light staying on after car dies, what else could it be??

[boston325]

Hi brian, i have the done the bulb test on the fuel pump - this is exactly what happened - after connecting the buld to the fuel pump terminals, turned the key to ignition - no light- as i cranked the engine the light came on strong and constant, as in no flicker, the engine died first and the light stayed approx 1 - 2 secs after the car died and then the light turned off.
Is this normal?
I also did the test on the ignition coil and the flow of current is constant , no flicker

i'm really stuck now????? think i've tried everything apart from a new ecu?? could it be??
your help much appreciated brian

[Brianmoooore]

Fuel pump itself is under strong suspicion! If possible, listen to it, and hear if it stops a couple of seconds before the engine cuts.

[boston325]

was looking on the net - found a 325i auto breaking local - i ended up buying a fuel pump and another crank position sensor - as few mechs have said and also read on internet that even new crank position sensor can be faulty - i believe that as i know of 2 people where it happend - a merc coupe and bmw 728i!!!! - but even with these 2 parts the car still does the same !!!! I thought maybe the fuel pump is pumping but breaking down under pressure
Now i think i have tried everything possible aprt from ecu ??

[Brianmoooore]

I've come across more than one E30 fuel pump that worked perfectly in its original home, but has become faulty once removed and stored for a while, so I still wouldn't discount it yet!
Take out the fuel pump relay, and link together pins 30 and 87 of it's base. This makes the pump run continuously. Run the car like this, and if the pump is still running after its cut out, then the pump is innocent.
ECU failure is extremely rare, but the very last case of cutting out I dealt with (cutting out when fully hot, after fifeteen miles or so or hard driving, restarting almost immediately, then missing and cutting again after a very short while) turned out to be the ECU in the end!

[boston325]

Hi, guess what - i took out the ECU to see the part number and left it on the window sill in my house, refitted it this morning and noticed two wires hanging near where the ECU is situated- Maybe used for earth for something - anyway refitted it and turned the car on and i thinks its sorted!!, what i think the ECU has been taken out at some point, refitted without connecting the two wires which were hanging and just left in place, and maybe not getting good earth, but saying that i have owned the car since 2002!! Now i dont know whether the ECU is at fault or the two wires were loose, or something that i may have knocked near the ECU area ??

[Brianmoooore]

Only earthing point for the ECU is on the top of the RH front suspension turret, and the rest of the wiring to the ECU goes straight out through the bulkhead and into the engine compartment.
What ECU do you have? The 380 is known to be prone to developing idle problems, in that the engine will stall if left to its own devices, but this shouldn't make it 'cut out'.
If the problem is solved, it sounds like you either have some corrosion in the ECU connector, or there's a 'dry' solder joint somewhere inside the ECU.

[boston325]

I'm going to try another ECU over the weekend, secondly i'm going to trace and follow back the 2 wires that I saw and see what is the oher end. I think we've got close to the problem now,

[boston325]

I have finally found the problem, the 2 wires which were conected with the ECU's 4 mounting bolts, 1 of the wire was corroded and giving limited connection, the wire I believe is linked to the alarm/immobiliser. I cut back the wire, rewired with new and reconnected, the car starts and idles as normal now!!!, who'd of thought, 1 rusty wire led me to spend £100plus on new sensors and parts, well atleast I know the car is good for a fair few miles to come.
Problem solved after 2 years when it originally started on bank holiday in august of 2007!!!
Due to time I left the car parked up, only 3 weeks ago I decided to fix it and now with your help and guidance guys its sorted!!!
Thanks till next time - (hope there is no 'next time')!!! lol