Possible Emissions System Fault?

[MrBloxz]

Hi all

I own a 1993 Volvo 240 Torslanda, its ran perfectly for the last 2 years but recently I've had an issue where the engine cuts out.

The first time it happened was during deceleration towards stopping at a zebra crossing, the engine cut out but started again straight away by turning the key.

The next time I used the car I managed to drive 6-7 miles normally to the shops fine but on the return journey it did exactly the same thing at a set of traffic lights , approximately a mile down the road at a speed bump it cut out again and when I turned the key it was idling at about 1500rmp and intermittently lost revs until it cut out at the next set of traffic lights, I managed to get home but it cut out another couple times on the way.

When it cut out the 3rd time a dashboard light came on with the lambda symbol which I have read relates to Emissions systems?

The car has recently developed a small hole in the exhaust but its past the cat so I wouldn't have thought it could be that

Anybody have any idea what could be causing this issue?

Thanks
Kallum

[Bugjam1999]

Hi,

So the engine cutting out going over a speed bump sounds like a loose connection to me, which you might be able to trace by wiggling wires with the engine idling- I’d start with the wiring for the crank sensor first, but there are other potential culprits, the ignition amplifier is another.

The lambda light on the dash indicates that there are fault codes stored to be read in the diagnostic system (which may or may not be related to emissions, there’s just one indicator light for all codes).

This gives an overview of how to read the codes- your car will have a black diagnostic box on the bulkhead on the near side (passenger side) of the engine bay under the bonnet.

https://www.volvoclub.org.uk/faq/EngineOBDCodes.html

Have a read of that site and see if you can read the stored fault codes.

Then as above I’d try letting the engine idle and wiggle wires to the crank sensor and the ignition amplifier as a start, others may have other suggestions.

Cheers

[Bugjam1999]

Similar information with some helpful photos in this thread:

https://www.volvoforums.org.uk/showthread.php?t=122391

[MrBloxz]

Originally Posted by Bugjam1999

Similar information with some helpful photos in this thread:

https://www.volvoforums.org.uk/showthread.php?t=122391

Thanks for the info, checked it and got a 1-2-1 so looks like its Mass Air Flow Meter related

[Bugjam1999]

Fair enough- several on eBay for around £40 or so.

There have been various threads on line saying the cheap aftermarket ones rarely work/fail quickly, so I’d go for a secondhand original one.

They’re easy to fit.

Cheers

[Laird Scooby]

Before you splash out on a new MAF, check all your fuses are pushed fully home, they often work loose, particularly in the fuseboxes hidden behind ashtrays.

If all is well, pull each fuse in turn and check the blades aren't oxidised/dirty due to age - if necessary clean with either some emery tape or a brass wire brush or simply renew, regardless of whether it's blwon or not.

Also inspect the fusible link inside each fuse for hairline cracks, this can also cause the same effect.

Along similar lines, check the hoses from the MAF to the throttle body and the AICV for security and splits - anything even not quite right here will throw a MAF sensor fault, especially if there's a split that opens up as you go over a bump.

If you do fit a new MAF, pull the memory fuse for the fuel ECU to reset the ECU and its fault codes. On the 7/940 it's fuse #1, not sure if it's the same on 240 models but probably is.
Refit a couple of minutes later before trying to start the car.

[Clifford Pope]

I agree the MAF convoluted hose is prone to splitting. It tends to split along the corrugations, failing as the engine rocks, or if ther hose is rubbing on the inner wing.
Splits can be very hard to spot. Try in the dark shining a torch along it from one end while blocking the other and flexing the hose.

[Bugjam1999]

This is all good advice- hoses are cheap and easy to replace and it’s possible one has split, as others have said.

I wouldn’t try and find a break, I’d just buy a few metres of new silicone 4mm hose and some decent zip ties and replace them all - chances are they haven’t been replaced before.

Also, you could take the existing MAF off and clean it using a can of spray MAF cleaner, since that’s also cheap and quick.

Since it’s a 240, it’ll have cylindrical fuses not blades and they can be a bit fickle- pull them all out and clean them and the contacts they fit into.

After putting it back together the codes can be cleared using the guide I linked to above, so clear the codes and then take it for a test drive to see if that fixed it.

Cheers

[Laird Scooby]

Originally Posted by Bugjam1999

This is all good advice- hoses are cheap and easy to replace and it’s possible one has split, as others have said.

I wouldn’t try and find a break, I’d just buy a few metres of new silicone 4mm hose and some decent zip ties and replace them all - chances are they haven’t been replaced before.

It wasn't the vacuum hoses i was referring to - they obviously need checking as well.

The one i was referring to is the one covered in aluminium tape on mine :



Note also the plastic plumbing fitting for the AICV take-off!

The hose between the MAF and throttle body on mine is made of what appears to be extruded or possibly vacuum formed polyethylene/polythene so gluing it isn't really an option.
The stub for the AICV was originally welded in but had split round the seam where it joined the main hose. Hence the plumbing fitting to feed air to the AICV, only way i could get it to not leak!

Also the reason for the aluminium tape is firstly to protect it from heat and impact and secondly because it had developed pinholes during the 30+ years it's been on the car. No doubt from the heat from the exhaust manifold!

The added benefit is it keeps the air inside cooler so it's more dense when it actually reches the cylinders! Certainly made it feel livelier after adding the aluminium tape!

Any leaks on this hose, the convoluted one that joins it to the MAF or any of the hoses to/from the AICV will throw a fault on the MAF so well worth checking them thoroughly and not assuming - if in doubt make sure it's tight with a Jubilee clip and/or replace the hoses if available - mine wasn't!

As for the Continental fuses, i'd forgotten about them being in the 240 - a 1/4" or 6mm drill bit between the fingers is ideal for cleaning the contacts in the fuse box and refitting the fuse and spinning it round several times is a good way to clean the contact points quickly and easily - free tip of the trade there!
Be warned the fusible link on them is fragile at best so be careful!