320 has developed a stutter

[Tom202]

Evening all.
My cars developed a problem where it stutters intermittently, very odd and i cant think what is wrong with it. As far as i know the fuel pump is a good one, at least its not whining like the one i replaced. I have recently replaced the crank position sensor, as that just packed up. The fault I'm experiencing feels very much like when the CPS was dying, but surely it cant be that as its a brand new sensor? Has anyone got any ideas? I'd like to just ignore it and hope it goes away, but i don't want to end up stranded again.

Any help would be appreciated,

Tom

[Jim320i]

Have you checked over all the obvious hoses for leaks? Dont rule out the cps problem just because its new, it could be faulty, or the issue could have been something else in the first place which in turn is causing that to play up again.

[Tom202]

Cheers for the quick reply jim. I have checked the hoses yeah, they are all intact and there are no obvious leaks. The stutter is quite violent like the ignition system is cutting in and out. Could it be a dodgey relay or something like that ?

[Jim320i]

Might be btter waiting for someone with a bit more experience as everything I have learnt is through mine playing up.

Check the engine cap too as it sounds to me like air is getting in somewhere it shouldnt but i'm probably wrong.

Check over the rubber boot section thing that runs from the afm to the throttle body as you may find a big hole in the bottom of it. Mine has a slight tear in it and that affects itquite a bit. Best just to take it off and have a look rather than feeling for one though as they go unmissed.


If not, i'm not sure, but someone will be along with a better answer any moment now.

[eddieg]

Replace main and fuel pump relays? Cheap.
AFM problems - check out the threads on this. U tube video on overhaul. Try replacement/second hand or known working afm from another car?

[Brianmoooore]

What does the rev counter do when it stutters? Just drop slightly to reflect the reduced revs, or try to drop to zero?

[Tom202]

Hi Brian, Thanks for the reply. Not sure what the rev counter was up to, but it just completely conked out, so i have the checked the crank sensor again, as i have only just replaced it, and found it to be faulty, again! Is there a reason why my car is eating crank sensors ?

[eltel]

make sure that the crank sensor isnt catching on any of the pulleys,very common problem to wear through.??

[Tom202]

Yeah, I have had a good look over it it, there is no physical damage to it

[eltel]

have you ever tested the old crank sensors (if you can).. ?? maybe a dodgy connection on the loom multiplug and by refitting a new one you are disturbing it into working for a while.

had this happen on a old one, 3 new sensors till i figured it out!!

[Tom202]

Yeah tested both of them and they were both knackered

[eltel]

very strange!! i will have a think but brian is your best bet on technical phenomenon.. cheap sensors??

[Brianmoooore]

The sensor consists of a coil of very fine wire wound around a magnet, so until the insulation begins to fail and moisture gets in, they should be 100% reliable - as long as they aren't savaged by the water pump pulley.

[eltel]

again brian will be the most help but im sure there is no battery voltage etc going to the sensor, was thinking about a surge of unregulated power breaking it but i dont think it can be...i cant think what could be causing it to fail so quickly

[m_jermyn]

How do you test the crank position sensor and what exactly are the symptoms of a faulty one?

[eltel]

Disconnect it from under the diagnostic socket then measure the resistance across the two pins nearest to the lead. Should be around 540 ohms and stay somewhere near constant with you wiggling the wire

[eltel]

sorry forgot to answer the 2nd part.. when they start to fail the engine can cut out for a split second as you're driving along then return to normal.
they can cause starting/running problems and when totally gone you wont start the car!

if the cps is faulty you will almost certainly have some major running fault

[m_jermyn]

Hmmm sounds like this could be my issue. The CPS is a month old too. My car has developed a stutter and yesterday it even cut out. Will be checking today for a faulty one.

[eltel]

also check your wiring underneath the inlet manifold..also give it a wiggle with the car moving to see if it alters the engine speed etc.

from there you could be looking at fuel pump testing etc

[Tom202]

If moisture got into it how long would it take to kill it? There have been some pretty bad floods up here in the lake district and the old girl has been ploughing through, thought they hadn't caused any damage though

[Tom202]

New sensor came today, i fitted it, the car started up, and got to the petrol station... then it broke down. there is petrol in it yes. i am not getting a ready of around 500 across the pins in the sensor, it cant possibly be that my car has destroyed 3 sensors can it ? someone please help!!

[Tom202]

reading* of around 500 ohms even

[Tom202]

And now it has just started it up again. Does anyone have any idea what this could be ?
EDIT

Now it wont start again, this is driving me mad, my dad has suggested it could be an ignition amplifier, does this car have such a thing? could it be a break in a wire somewhere ?

Edit again

I have just checked the resistance across the pins on the cps and i am now getting no continuity across it at all, but earlier i was getting 800, this is very confusing

[Brianmoooore]

What does the rev counter do when it stutters? Just drop slightly to reflect the reduced revs, or try to drop to zero?

[Tom202]

Sorry Brian,i am not sure, i haven't seen what the rev counter does as it was only a few seconds of splutter. The problem has really developed now though, to the point where i don't want to drive the car.
The car seems to start when its been left for a few hours, but given a few minutes run, if you turn it off, and go to start it again there is no spark.
I have changed the CPS twice now, both times the sensors have been brand new, but both times i have had high readings of resistance of around 800ohm, and the new sensor sometimes i dont get a reading at all.
Is there a chance that i have wrecked the sensors before fitting them by continuity checking them with my multimeter? I have been talking to a mechanic who says the problem could be to do with the ignition amplifier, which i am told is in the ecu on the motronic system?
Can you just straight replace the ECU on these cars for another motronic unit?
Also, i have just been out to the car, i tested the resistance across pins 1 and 2 of the CPS, and got a reading of 800ohms, then i started the car, and left it running, until after about 15 mins it conked out. Took another reading across pins 1 and 2 of the cps, and the resistance is now so high the multimeter cant read it. Can you think of any explanation as to why this is happening?
This car was my pride and joy, but its really let me down recently, need to get her going asap as i live in the lake district and am very stranded where i am. Any advice is gladly recieved.
Thanks

[Tom202]

Anyone got any thoughts ?

[kman82]

if you can get it going I would really try and answer Brian's question and then he can help you out...

What does the rev counter do when it stutters? Just drop slightly to reflect the reduced revs, or try to drop to zero?

[Tom202]

well it doesn't stutter any more, it just dies, completely, then wont start up again for a few hours

[Brianmoooore]

Plugs wet after cranking or not?

[Tom202]

Yeah, it is definitely getting fuel. It is like the sensor is overloaded and will only work for a certain amount of time, is it possible that i have damaged the sensor by continuity checking it accidently? Or that some wires are shorting at putting a current through the sensor and damaging it?

[Brianmoooore]

Sparks at the plugs?

[Tom202]

No, once the car packs up there is no spark

[Brianmoooore]

Connecting battery voltage straight across the sensor would only flow a current of 20 odd milliamps, and dissipate around one third of a watt. Can't see that doing any damage.

[Tom202]

Do you think that it could possibly be a duff sensor then? As the varying resistance across the pins confuses me a lot. As i said, starts off about 800 ohms, then after about 10 mins of running, the car packs up, and the meter across the two pins reads an open circuit.

then if you leave it for a few hours, it comes back to 800 ohms?

[Brianmoooore]

If there's no spark at the plugs, then they shouldn't be getting very wet with fuel either, as the fuel pump shouldn't be running.
The resistance measured across the crank sensor when unplugged from the engine loom, should be consistent, apart from a very small temperature related change.
Going open circuit after a few minutes of running is typical of a failing sensor.