E30 Zone

Hi Guys,

Ok I've started this new topic as I thought the old title could be misleading and, having now done abit of trouble shooting, I can rule out some could be's.

Basically my car is running really rough and cutting out once warm. It can just about idle when it's cold, once it's warm it won’t idle, revs drops to almost stalling before it revs itself back to circa 1000rpm and then eventiually cutting out. If you rev it it doesn't rev cleanly till above 3000rpm, you can hold rev's and it won't stall. You also need to use the accelerator to start it other wise it won't start.

Once it's warm and cut's out it, you can start it a couple of times. Then, if it stalls again, it won't crank??? Before was making a clanking/loud clicking noise now I get nothing. The lights on the dash board dim and the little lights above the headlight switch go out when you turn the key but now cranking or any noise? If I leave it over night it will then crank and fire fine until it's warm then I get the above?

When it's cold and you start it the battery light stay on as does another light with the( ! ) On it until you rev it, then these lights go out.

Have replaced AFM with known working one”¦no change
Checked plus and leads (not done a multi-meter test yet though)
Spayed brake cleaner around the inlet, (made no difference to warm idle although I may have been spraying in the wrong place)

Am going to attempted to remove pulse sender tonight.

The main trouble is that once it's warm and being an auto it cuts out when you come to a junction etc then won't start hence I can't really drive it outside the village I live. I'm don't wanna go replacing a load of bits that don't need replacing and frankly can't afford too. The car is an 86 325i auto, I have an 89 325i manual that I can use for parts if they can be interchanged.

I love the car to bits and want it back on the road, advice needed please. My mechanical knowledge is limited so please explain like you would to a 10 year old.

willnz wrote:The cutting out could be caused by insufficient voltage being supplied on idle due to bad connections/earth/faulty alternator etc so go through all of the above.

Yes, this is almost certainly all due to the engine being starved of electrical power!
Have you measured the battery voltage, with and without the car running?

Thanks for the replies guys. No i will get a multimeter tonight and get testing.

It's a very good suggestion and one that i had not thought off. Just before the car started "behaving" like this we were driving through a very bumpy car park. It could be that one of the earths has worked/come loose.

The battery terminals are fine and the battery is a genuine BMW one.

Thanks

the battery connections may be fine, but the connections of the negative (dont like calling it Earth or Ground as it is neither!!) to the car body/chassis may be loose or corroded, and pay close attention to the straps from the alternator to the body.

with your meter set on DC volts measure across the terminals, yoou should have about 12.5 volts with engine off, and about 14 volts with engine running ona fast idle.

Tested the battery with engine off and get 12v, 14v with engine running. I also disconnected teh battery negative whilst engine running and it continued to run so i think the alternater is doing it's job.

Checked battery earth, alternater earth and they appeared fine and well connected.

Removed the dizzy and cleaned the points up, the spark plugs are now covered in black soot so it's not burning the fuel.

I also removed the HT leads one by one whilst the engine was running (only got belted once) and there was no noticable difference when i removed cylinder 5's lead??? That plug was the most black.

Going to try a new set of plugs and leads but have you guys got any other ideas? I think the plugs went like this due to another problem as when i checked them before they weren't as black. Maybe the constant cranking and running of the engine for a short while has made them go like that???

EDIT, it also didn't stop cranking yestarday. Before, after a short while, the car wouldn't crank. You'd turn the key and nothing but yestarday she kept on going.

My M30'd car was showing the same hesitancy/spluttering/bad idle until yesterday, solved it (eventually) by unplugging the lambda sensor which must have been fubar'd during a recent exhaust system swap. I think the car must have been running hugely rich, and unplugging the lambda means the ECU uses a default fuel map instead.

Just mentioning it in case your car has a lambda sensor in the exhaust - catalyst equipped cars only I believe.

SteSE wrote:Checked battery earth, alternater earth and they appeared fine and well connected.

Did you remove, and sand/clean/refit these connections? Often they "look" fine, but have corroded where the spade connector meets the car chassis.

Martin.

Not sure if it will have a lambda sensor, doubt it as it's an 86 car but will check. It should be on the downpipe of the exhaust manifold right??

Your right in what you say, i didn't remove clean and replace the connectors. Just gave them a tug and breif visual look over.

Whilst I still think that earth straps are the most likely cause, another possible might be the blue temp sensor that tells the ECU coolant temp. You can measure the resistance across it's two terminals, and see if it is working correctly. The correct resistance values are somewhere on the board, but on my M30, it reads about 210 ohms at normal operating temp. If this sensor is faulty, the ECU may think the engine is always cold and vastly overfuel.

Yes, lambda is likely to be at the bottom of the downpipes.

Martin.

Yes was a bit foolish not to remove them and give them a clean, will do so tonight if i get a chance.

Car seems to warm up as normal, the temp gauge goes up as normal.

One thing though is that the fan seems to be always on, even from cold??? And, i get a big whoosh when i rev the car. Not sure if it's normal or not?

SteSE wrote:Car seems to warm up as normal, the temp gauge goes up as normal.

There are two temp sensors, a brown one for the dash gauge, and a blue one for the ECU signal. Completely separate.

No real clue about the fan question Im afraid as my car has an electric fan, but my E32 735i viscous fan always rotates regardless of engine temp. Slower when cold though.

Martin.

AHHHHHHHHHHHHHHHHH

This thing is testing me.

So far to date have replaced ICV, AFM, Pulse sender, checked/cleaned what earths i can find, tested alternator and have drained petrol and replaced with fresh stuff and it STILL won't idle when warm.

Any other suggestions before i smash it up

EDIT:- Idles fine when cold, for about 5 minutes and then hunts and stalls

Have just replaced the blue temp sender to no avail! any other ideas i will try anything

just a thought really but could it be a hole in a hose somewhere that opens when warm to let unmetered air in?

Your OP suggests you have more than one fault! Nothing to do with the engine temp sensor will stop it from cranking - that will be an electrical fault of some kind!
Similarly, if the warning lights don't go out until the engine is revved, you have another electrical fault, or the engine is idling very low for whatever reason.
Back to the temp related problem: Does the pre facelift loom have a C192 connector like the facelift one? Does it suffer from the same problems?

i had quite a lot of these faults your describing on my old 320 auto, and i put an ecu on it in the end, and it ran fine and still is! im not saying this is the fault with yours but if you had one readily avaliable might be worth a try

cheers ash

Hi guys thanks for the replies.

Brian, the only fault now seems to be it hunting then dieing after 5/10 mins of engine starting. The other faults, not cranking after a while seems to have gone away. The dash lights will occasionally stay on when started until the engine is reved but this is when the engine is warm and not running correctly and attempting to idling around 500 rpm mark. A quick rev and the dash lights go out.

The car starts and idles fine from cold for about 5 or 10 minutes. After this it starts to hunt slightly for another couple of minutes. This progressively gets worse until the engine stalls.

Brianmoooore wrote:Back to the temp related problem: Does the pre facelift loom have a C192 connector like the facelift one? Does it suffer from the same problems?

It does have a connector but not as big as the facelift one, i'll get a photo tonight to show.