850 2.5L 1996 intermittent stalling

Hi All,

Just putting this out there in case anyone has heard of a similar case
and there is a straightforward answer.

I have an 850 2.5L 1996 (Fenix 5.2 fuel system) which this last week has
begin stalling intermittently during normal driving. There is no common
conditions - hot, cold, uphill, on the flat - the engine stalls.

It happened to my wife at first and I had thought it was perhaps due to
something simple like the idle speed being too low but tonight it has
happened twice to me during normal driving conditions. Then engine just
dies at normal revs.

It is a bit disconcerting of course. The second time it happened tonight
it was difficult to start again. When the engine did take it was not
idling smoothly for a couple of minutes but that might have been becasue
it was too rich. The engine actually runs beautifully so i don't think
it is related to plugs or HT leads.

I checked the ECU for the fuel injection reports 1-1-1 - no error.

I need to investigate more tomorrow when it is daylight but would an
clogged airfilter cause this sort of behaviour?

Any other suggestions would be appreciated!

Cheers
NK

 

Does the tachometer drop like a rock when it stalls, or does it follow
the engine RPM down? Does the ignition system display any codes? A
clogged air filter will normally make the engine feel low on power, but
random stalling is not a problem I'd expect from that.

 

Hi,

If you haven't had this problem before, it's probably time. It's the rubber
elbow on the alternator end of the inlet manifold, which is very hard to see
and reach. It connects to the other side of the manifold near the flame
trap. The rubber elbow perishes and goes soggy and sticky and eventually
gets a hole which lets air into the manifold. You will eventually get an
error code (I got 2-2-1 "long term fuel mixture too weak in part-load
stage"), but before that the idle speed will play up.

Mine eventually started making a lot of noise which is what led me to it.
Before that I had unusual idling problems.

I bypassed the original piping layout due to it's inaccessiblity and ran a
piece of rubber tubing over the top of the manifold to the flame trap, and
held it in place with cable ties.

To check it, try poking it with a thin stick, or try and get you hand in
there when the engine's not too hot.

Regards
Barry

 

Many thanks Barry for your excellent insight.

I had a good root around the engine today and I think I found the elbow/
tube you meant (see http://picasaweb.google.com/lh/
photo/8ctZn9vdvaVtDaVco2TkwQ?feat=directlink) but it looked fine to me
other than a little orange/brown residue in the tube - is that normal?

Is that cylindrical part the 'flame trap'?

I also noticed the similar pipe heading off from the manifold to a sensor
above the radiator which reads the manifold pressure (the 'Manifold
Absolute Pressure Sensor'). I am suspicious of this because it has the
capability to stop the engine immediately.

I dismantled the MAP setup and everything seemed to be in order (see
http://picasaweb.google.com/lh/photo/EsFCWVqDuXvkvB_w3PpLSA?
feat=directlink)

After I disconnected the sensor I got correctly got a 1-2-1 error about
the MAP in the ECU and the 'lambda' sign on the dash. Previously I have
only got 1-1-1.

So would a faulty sensor be able to stop the engine and *not* register an
error with the ECU?

I reassembled everything and took the car for a test drive but only got
about 100m down the road when the engine cut out without warning. I then
started it again and took it for a 15min ride without incident.

Still scratching my head so any ideas gratefully received,

Many thanks
Noel

 

Hi Noel,

No the hose you are pointing at is the vacuum line to the fuel rail pressure
regulator. (It is in my car anyway.)

The elbow I'm referring to is more to the left and lower down. Look in the
small gap just to the right of the power steering fluid container and the
left end of the inlet manifold where the 5th inlet runner pipe (not quite
shown in your picture) joins to the "large round part that goes to the
throttle body on the right". Under the top radiator hose. It is hard to
reach with your fingers.

The elbow is also larger in diameter to the one in your photograph.

I wouldn't expect much residue in the pipe from the fuel pressure regulator
unless the regulator diaphram has a leak. Much like the pipe to the MAP
sensor. There shouldn't be much airflow back and forth. Shouldn't stop the
engine suddenly anyway.

As your engine is actually cutting out whilst driving, I think you might
have a different fault to the air leak I suggested you check for. Mine when
leaking badly didn't stop the car, merely brought up the engine fault light
and mucked up the idle.

I have a copy of an article from an English magazine from about 10 years ago
which describes the Fenix engine management system on the Volvo 850 in
detail which I can email to you if you give me your address (about 8.5MB).
It might help you.

Most engine sensors are monitored for readings which are out of normal range
and the ECU will report a problem. But the ECU can only report what the
designers have told it do, and they can't foresee all the problems that
might occur.

A sudden engine cut out like you describe seems to me like an electrical
fault, and you do really need to find the actual fault itself rather than
try things and hope you fix it. You need to know that it is fixed, and to
do this you need to locate a fault. Intermittent faults, particularly in a
(moving) car can be very difficult to locate. You probably realise this by
now anyway.

I live in Western Sydney, Australia, a very mild climate and very kind to
cars. I wonder where you are and is your car likely to suffer from
corrosion due to weather conditions. There are many connectors in a modern
car that can give trouble, including earthing points for various components.
The earthing for the "ignition amplifer" is a known problem in the 850. The
article I mentioned points this out. I believe the ignition switch itself
can be source of problem too, particularly if a heavy load of keys is
regularly swung from it.

Lastly, and this also won't stop the engine immediately is the ignition
leads. I had a slight miss when my car was about 6 years old, which got
progressively worse. It turned out the plastic tubes that fit inside the
engine to carry the current to the spark plugs were progessively breaking
down and arcing to the engine. Worth checking occasionally. Also have you
had the ABS module fail yet? It is a do-it-youself repair if you're
competent with electronic printed circuit board repair. Merely needs some
joints resoldered. Also the airconditioner evaporator (the inside the car
bit) should have needed replacing by now )

regards
Barry
(barvic139_at_internode.on.net) remove the "_at_" and replace with @

 

Thanks Barry. I had to leave the car at someone else's house but I'll
try and track down this pipe later when I cycle up there. I think you
are right though that the issue is not the same.

I took the car for a spin yesterday and it was fine until the return leg
when the engine cut out whilst climbing a hill. An interesting clue
which (I had noticed previously but could not be sure about) was that the
engine seemed flooded when it was restarted. Really flooded - very
strong smell of petrol and the engine was struggling to idle. If you put
any revs on the engine it cut out so I had to let it idle for a minute or
so until the richness had cleared and the engine settled down.

So I am thinking now that there is a problem with the fuel mixture or the
perhaps a fuel blockage or something? Fuel pump stopping?

I live in London and the only problems we have ever had with the Volvo
are when we have had very hot summers (ie not very often!). The car has
always been very, very reliable.

I'll read around the fuel system I think although I guess there should be
something logged in the ECU for a problem like the fuel pump cutting out.

Cheers
Noel

 

Is that white /grey colour on the pipe you have in your picture a sign of
arcing from some electrical source ?
I once had issues with old rubber boots on the spark plug leads shorting out
in a V6 Volvo they had become conductive
with old age .

 

Hi Noel,

Don't forget the obvious (and cheapest to fix), the fuel filter.... Also
you'll probably find some details on the wed re problems with the fuel pump
relay. I've seem them mentioned before, but they might not refer to 850s.

Though I wouldn't expect a fuel stoppage to cause engine flooding. See my
previous mention of your vacuum pipe to the fuel pressure regulator. It
should be clean inside unless there's a (fuel) leak in the regulator
diaphram itself. That could cause richness problems, as petrol would be
sucked into the inlet.

Anyway these are just thoughts, hope you locate your problem.

Barry

 

Fuel pump relays often have dry joints (usualy volvo thing) - can you hear
the pump prime when you switch the ignition on?? It is on the underside of
the fuse box, accessed from under the bonnet..

And secondly, ignition switches themselves can get intermittent. Especially
if your keys are a large heavy bunch. With the engine running- try wiggling
the key around - if it splutters you've found the problem.