850 engine cuts out

Help! My 850 2.5 10-valve sometimes cuts out on a right turn, which
is very inconvenient on roundabouts in the UK. The symptoms are: 1-
the engine dies and will not re-start. 2- the engine cranks but there
is no spark at the coil. 3- when you turn on the ignition the
temperature gauge goes right up, then right down even though the
engine temperature is normal before it cuts out. 4- after about 40
minutes it will re-start and the temp. gauge works normally. It has
happened twice now, and after the second time the Lambda light has
stayed on. After the first time I did 150 miles, threw the car round
lots of right turns (which was fun) - no problems until yesterday,
when it died on a busy roundabout. Please can someone help? Or
should I re-plan my routes to always turn left? Could it be an
immobiliser fault? (I did try switching the immobiliser on and off but
no help). Thanks, Marvin

 

Tricky one!!

I would suggest you check the connections at the ignition coil, and
under-mounted amp, and especially the earth ring connector that is trapped
under one of the bolts. Remove the coil unit entirely, as its often painted
under neath and the earth connection is less than ideal electrically.

Also check the King HT lead is properly restrained in the clips around the
air filter, and the Air temp sensor wiring is routed as far away from the HT
lead as possible.

Also check the Cam Position Sensor (CPS) wiring plug on the end of the
exhaust cam, and the Crank Angle Sensor (CAS) plug wiring below it.

I am mystifed by your weird temp gauge readings,- it may well the ECU is
being spiked by stray HT, but it should restart straight away though.

Tim..

 

Thanks Tim, I had checked the wiring but not the coil earth - I will
do that. It's tricky to find a fault that has gone...

 

But it's not entirely gone. You have a code stored in the ECU that
caused the Lambda light. That code should point you in the correct
direction.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Thanks guys. Today the car stopped again, but I had my trusty
voltmeter with me. I measured the voltage on the coil: ignition on -
nothing. Cranking - 12v to chassis on both red and blue wires, of
course no voltage across the coil. I tried earthing the coil body/
amplifier heatsink - no change. I don't expect either coil connection
to be grounded but the fault must be in whatever it is that drives the
coil amplifier. Time, I thought, to read the fault codes: Socket A
pins 2 and 3 give 1-1-1, socket B pin 5 gives 1-1-1. None of the
other pins give any flashes. I hope this means something to
someone... the temp. gauge was doing the same thing: switch on, the
needle goes to halfway, pauses for second, then goes right up, pauses
for a few seconds then falls to zero. After an hour and a half, as I
was attaching the tow rope, my wife tried the key and she fired up,
drove home with no problems. I didn't mention it before, but the
central locking gives trouble in damp weather, especially the
tailgate, and the remote often will not lock the doors although it
will unlock them after I have locked them manually. Could this be an
immobiliser fault? Where is the immobilser located, and can I disable
it?

 

No, it wont be an immobilizer fault, as it is inhibited whilst the engine is
running.

Seeing as you had no +12v at the coil with key on, I would head straight for
the main relay (underside of fuse box) Sounds to me that the ECU is not
powered up when it dies. - dry joint in the relay.

If you can- check for +5v at one of the engine sensors (pin 1 if its a 3 pin
connector) the next time it quits. If 0v the ECU is not powered.

Either replace the relay, or open it up and resolder the PCB.

Tim..

 

Hi again just an update... the ECU was still powered because it
started the fuel pump briefly when the key was turned. Someone on
another forum suggested the coolant temperature sender - I replaced
that, and the thermostat as well because you have to remove the elbow
to get at the sender, and the car has not broken down for 40 miles so
far (it wouldn't do more than 10 miles before). The only trouble is
that the idle is now down to 550 RPM hot or cold, and it stalls
easily.... I think I'll start by cleaning the idle valve, but what
next? Cheers, Alan

 

Pull the codes. It will most likely be the camshaft sensor. I had the same problem, having the engine die for no apparent reason and not starting at all. Replaced the cam shaft sensor and she runs like a charm now. Maybe change the fuel relay while your at it.