325i running probs

[staley_turbo]

This was the first proper drive in the car today. It has a little running issue.
Every now and then it will lose power. I could be cruising or accelerating. Pedal could be flat or 1/4. The power will die - around 30 secs later it will be fine. When it loses the power, i can take it out of gear and it will idle fine but doesn't want to rev.

I have changed the afm.
I have put new plugs in.

Any ideas?

[eltel]

i had the same prob with a previous 325i... totally intermittant with no pattern, i replaced the throttle position switch which helped slightly, but the cure was a new ecu. i think either the chip or actual ecu itself was at fault.

[staley_turbo]

Really? that would be the last thing i would of thought. Ill try a new one if i can find one.

[eltel]

i said exactly the same..i tried valve clearances compression checks, ht leads, dizzy cap and rotor, the tps, checked the wiring plug beneath the inlet manifold (which you should check incase it has corroded)..i changed the white dme relay and orange fuel pump relay...
eventually bit the bullet and an autoelectrician confirmed it was the ecu..replaced the ecu with a 2nd hand unit from here and instantly cured the problem

[staley_turbo]

Right, this still isn't sorted, I'm going to buy a ecu tomorrow but is there anything else it could be?
Today its had new arm and cap. Checked tps. Checked everything we could think of. I haven't checked crank sensors yet but these and not old, i have the receipt for them 5k ago.

[staley_turbo]

Does anyone know what pin numbers for the afm is on 55pin plug?

[clipper]

Just sharing my experience before you splash cash:

I had a similar problem, complete random momentary power loss, it went on for months until one day it died completely and wouldn't restart as it was electrically dead.

New brush pack on the alternator and the problem completely disapeared.

[staley_turbo]

Tried loads more bits today, i got another ecu that was broke - waste of time. Im going to get another ecu tomorrow. I have changed crank sensor, another afm, coil, etc...
Could it be ecu? are they a common problem?
Im not sure about alternator but i have brought a another one.
I put another fuel pump on today but im not sure its any good and it didnt solve the problem, maybe made it worse.

[JoeDiese]

Are you sure it isn't something silly like a clogging fuel filter or something?

Are you certain you're looking at an electrical problem?

If it is electrical, have you replaced the DME/"Main" Relay (the frontmost of the three)with a new one?

[beemerbird]

I think you are not helping yourself by fitting parts of unknown provenance on your car. A new fuel filter is less than a tenner, and it'll do your car no harm. If you carry on fitting an assortment of potentially dodgy scrapyard finds I doubt you will ever solve your problems

[staley_turbo]

New filter today. But the fuel in the tank is stale. I think its a electrical prob but i cant tell. I have not replaced any relays, i have checked them and they seem ok. Its a intermittent fault but is starting to happen more often, say every 30secs it will die.

[staley_turbo]

I cant say im happy with the parts im putting on it. Im buying nearly everything new apart from afm, ecu and fuel pump.

I can leave it ticking over and it will start to idle lumpy, if you try to rev it, it will pop and bang and somtimes rev.

[beemerbird]

How long have you run the car for in total since it's been back on the road?

[staley_turbo]

I have probably done 15 - 20 miles due to the running problem. Its been left to tick over for half hour a couple of times, not much i know.

[beemerbird]

How long was it OFF the road for? Was the battery disconnected? Hope you haven't thrown out all the old bits

[staley_turbo]

I have only thrown the arm and cap as they were dead. It was last MOT`d in 2006 and ran out in 07. The battery was dead when i got it, im not sure if its been disconnected, what affect does this have?

[beemerbird]

Basically you end up with the ECU forgetting that it was designed to be the 'brains' behind the drive characteristics of the car. It has to effectively re-learn what it is. Were they timed half hours at idling?

[staley_turbo]

No, just while working on it, it was left to warm up or cool down etc.. Would an ecu off of a running car fix this?

[eltel]

I'm still thinking ecu.. Especially if it hasn't been used for 3 years.. Could be that the ecu has forgotten it's settings. Mine was off the road in bits for 2 months.. When I connected the battery it popped banged ran rough and wouldn't tick over for 20 minutes or so, then as if by magic it just started running sweetly bar some coolant issues.

[staley_turbo]

But this runs fine half the time?

[beemerbird]

I would stick with the changes you have made, set your stopwatch, and leave the car to idle for about 20 minutes. Then drive it. Then report back.

[staley_turbo]

Will do! I will give it ago now.

[staley_turbo]

No joy

[beemerbird]

Well, that's me out, I'm afraid to say. Good luck with it

[staley_turbo]

Cheers anyway. Another ecu tomorrow, another fuel pump as I'm not happy with the used one that I have fitted. Then testing the loom for faults or breaks. How hard can it be

[JoeDiese]

Erm, why are you going to continue to throw parts at this instead of diagnosing it correctly?

You say the gas in the tank is stale? Drain the tank and put some new in then. Stale gas loses it's volatility and wont burn right no matter what parts you replace...

I severely doubt the ECU is at fault, it won't forget how to make the car run, that's not how it works.

[staley_turbo]

The fuel doesnt explain an intermittent fault. The car would run poor all the time. I know how the ecu works but it was worth a try. The ecu could have a intermittent fault and without testing it I will not know. Have you got any other ideas ?

[eltel]

Not taking anything away from Joe but this is exactly how a 20 yr old electrical component could react if damaged internally... It is well written on here about them losing the settings and like I say mine did exactly what yours is doing..could drive fine for an hour then it would play up and go back to being fine.. The ecu cured it and it literally was the last thing I tried

[kevo]

have you looked at the injector loom? sometimes the large plug can corrode and when the engine moves around or you go over bumps the injectors can cut out intermittently. it's located under the inlet manifold and is routed through a metal bracket thats mounted to the manifold. when the engine is running while parked put your hand on this wire and move it around, if the engine cuts out or anything changes it's worth investigating.
cheers
Kev

[staley_turbo]

Ill give that a go. Sounds logical. Its not ecu, i tested today. I have brought a new fuel pump but not fitted yet as im draining the fuel first.

[beemerbird]

When you have the stale fuel out, fill the tank with as much fresh petrol as you can afford. Over time there may have been some deterioration to the inside of your tank (especially if it's been sitting) causing a rusty sludge to form. Obviously introducing a small amount of fresh fuel into this will leave you with a particle laden mix that will knack your new fuel filter straight away, whereas more fuel will give you a more car-friendly sludge to fuel ratio

[e30maddog]

it might even be worth takin it out for a drive and as soon as it starts the power loss symptom, put your boot down and pull over right after.. sounds strange but its gonna be down to fuel/spark/airflow. (supposeing your compression is fine) so try the above then after you pull over stick your nose up the tailpipe if it stinks of unburnt fuel, then that would at least point you to either spark/airflow... get the airflow meter tested too, if thats ok i would pay more attention to the electrical side. also what type of dizzy do you have? the one on front of cam or down the side above the sump? ive had a few of the 'down the side' dizzy lumps and all have given me problems.. and this would be a total long shot but i got hold of a second hand full exhaust syatem not so long ago, fitted it up and the car acted just as yours does, turned out that during its time of lyin around the scrappy somethin managed to find its way into the pipe.. i did hear somethin rattlein around when drivein but before i got the chance to rip it off and sort it, the item blocked the pipe and after the biggest blowback ever, the engine died and killed the afm, new afm and exhaust and problem solved... you havent brought a second hand exhaust have you? lol

[staley_turbo]

There is no rust in the tank, Ive had abit of fuel out and it is clear.Hopefully the sludge will clear itself, Its had new filter and a pump tomorrow. I will fill the tank to the top though. I will also add some fuel system cleaner.

Driving is not possible anymore, i struggle to get it to move. Compression is good. The exhaust was new a few years ago and is still mint, It smells of stale fuel. Dizzy is at the end of the head and is new.

I have started to check wiring today, but i need to go more in depth when i have some more time.

It will get sorted

[5six7eight]

Did you make any progress on this?

[aeberbach]

Can you solder, know anyone who can? I fixed an intermittent 325i cutout by reflowing all the solder joints in the ECU. Did everything else described here including mounting an inline fuel pressure gauge when I ran out of things to try. Soon as I touched up the solder no more problems. Solder is a brittle metal and 20+ years of vibration can easily cause joints that were not perfect to begin with to fail.