Engine: 2.0 Carb B200K/B200F: Air Mass Meter

[Angie]

Some time ago I started a thread about the unpredictable behaviour of the engine, and it seemed to be caused by a fault with the AMM, though other possibilities were suggested.

Anyway, after a lot of visits to the garage, and a chat with a very helpful man at Truro Motor Company, the problem does appear to be related to the AMM, though not necessarily the meter itself but more likely the connector. By moving it the engine speed alters dramatically, and the running varies from very rough to very smooth.

What I want to know is can a replacement connector be fitted, and if so does anyone know where to get one?

[stephend]

Did you wiggle or did he?

[Angie]

When I saw there was a reply I thought, hoped, it might be something useful!!

[tannachyallen]

I would try carefully cleaning all the pins and applying Vaseline or electrical connector jelly. Connections dry out and that plug is in a fairly warm area.

Dave A.

[Stephen Edwin]

I am very pleased that the actual problem appears to have been found at last.

I hope someone will prove me wrong but I suspect you would have to use a hopefully known good second hand connector. Possibly a part loom but that would probably be QUITE some task to fit. More likely a connector with a good length of cable/wires attached, to be spliced or fitted with a suitable connector to the car's wiring.

Originally Posted by tannachyallen

I would try carefully cleaning all the pins and applying Vaseline or electrical connector jelly. Connections dry out and that plug is in a fairly warm area.

Dave A.

Yes. I would first try say Contact Cleaner. It's a solvent and is not a good answer but it does often work. Maplin sell a reasonably priced aerosol spray, incluidng a "straw" for precise application. Or there might be a better way to clean the connections?

I have heard it claimed that even WD40 can help to clean contacts. I don't use that jack of all trades product except to disperse damp.

Originally Posted by stephend

Did you wiggle or did he?

Originally Posted by Angie

When I saw there was a reply I thought, hoped, it might be something useful!!

The information might help the experts to advise further.

[stephend]

Originally Posted by Angie

When I saw there was a reply I thought, hoped, it might be something useful!!

Ok, ok...! Do I recall correctly that you'd already tried swapping AMMs and the problem remained? If so, it's not the connector on the AMM itself, but must be the cable or plug that connects to it - in which case, as Stephen Edwin suggests, it's a case of replace or repair.

It's certainly worth trying contact cleaner spray, as has also been suggested, but check for green crystalline deposits (corrosion): if it has these, it probably won't clean up well.

I respectfully disagree with the suggestion re Vaseline: it's a non-conductor, so can't help with electrical contact. The reason you can get away with using it is that the act of making the connection scrapes away the Vaseline at the point of contact. What it is useful for is smearing over a contact that has already been connected (like battery terminals), in order to protect the assembled connection from dirt and water ingress.

The other possibility is a broken wire inside the insulation, making poor or intermittent contact where the broken ends touch. The best way to test this is using a multimeter to check for electrical continuity, wiggling each conductor in turn along its length until you find the dodgy bit. Sometimes it's obvious from external damage - or turns out to be where the wire turns through a bend, or has a cable tie round it, or similar - anything that might be associated with damage, flexing etc.

If you do find a broken conductor, you can clean it up and resolder, and re-seal it with heat-shrink insulation, also available from Maplins.

[Angie]

Thanks for the sensible replies! The plug thing which connects to the AMM seems to be the culprit as moving that really does alter the engine behaviour, from practically stalling to racing away at around 2,000rpm. Moving the wires at any distance from the plug doesn't have that effect, which led the mechanic to think that a new plug (connector, or whatever it's called) might be the answer. He's tried cleaning it and closing off the contacts a bit but no improvement, so maybe it's just where the wires actually enter the plug. I just wondered if that type of plug is obtainable new or if I'd need to get a s/h one and as suggested, have it connected to the existing wiring. Obviously a new one would be preferable, presumably that type of plug must have been used on quite a lot of vehicles so maybe someone still makes them.

[Stephen Edwin]

So out of interest, how many wires are connected by that plug?

Can a multimeter be deployed from each wire well back in the cabling to the correspnding pin of the plug, then move the cable and see if the resistance changes? This should only involve cutting open the cable sheaf and piercing the insulation of each wite with a seriously sharp probe.

Or, perhaps to confirm any apparent findings, cut open the relevant part of the plug itself, check the connection of each wire to its pin and move each wire in turn and observe the effect on the engine running. What voltage is involved? What insulation would be required?

If a problem is found re one or more wire, can it be soldered or similar to the plug?

Can individual connectors be used instead of the plug? Perhaps temporarily.

This would all be [semi] destructive testing re the plug, but what is there to lose?

All replies are sensible. Some replies are more sensible than others.


.

[stephend]

Multi-pin connectors on vehicles always seem to be unique to the specific application, so I doubt you'd get a new part from anyone other than Volvo.

From a technical point of view, a new section of loom, or good s/h, would be the best bet, although tracing the cable run and locating the other end might turn out to be a headache. Otherwise, the option of splicing in a replacement plug and cables to the existing cables is going to be the most practical. Making sound joins and protecting them is then the important thing. Unless you're a dab hand at soldering (like I'm not!!), you might consider farming the job out to an auto electrician.

I don't know about the AMM connector specifically (mine doesn't have this) but Volvo multi-pin connectors that I've looked at don't look like you could disassemble them non-destructively, unfortunately.

[classicswede]

If the plug is the problem and cleaning does not help I could find you one with some cable on it