Engine: 2.0 Carb B200K/B200F: Air Mass Meter

[Clifford Pope]

Good theory. The 6-pin AMMs I have are supported by a bracket which has two rubber insulating bushes on the securing bolt. But they have the 6th earthing terminal.

Does a 5-pin AMM have the rubber insulation?

I did a bit of browsing on LH AMM tuning sites, and discovered a community of people who tweak AMMs by varying the earth resistance among other things. Having the right AMM with an earth inlet to play with would obviously be important.
I don't understand a word of all this, it's real Classicswede territory.
It just made me think that perhaps earthing might be relevant in your case.

[Angie]

You're all brilliant, going to the trouble to try and fathom this thing, thank you.

I've just had a look at the Haynes 'spaghetti' wiring diagram and managed to locate the sensor there, component 215. Their most recent diagram is simply '1986-on', not really a lot of help as there seem to have been quite a few changes within the final years of manufacture. The diagram shows a six-connector sensor, but the more detailed diagrams on the thread I referred to earlier all show five contacts. In each case though contact no. 1 goes to earth. My car has only five wires, one to earth therefore, the other four to the ECU.

I consulted the local Volvo dealers, a very helpful bunch as I discovered, and they can get a sensor, for rather less than I paid Braydons, as it happens, but imported from Sweden. However the parts manager said he wouldn't know the number of contacts until it arrived and he could look at it.

I increasingly think that my six-year ongoing problem stems from someone unknowingly fitting an incorrect part. When that part failed I ordered a replacement but inadvertantly compunded the issue by merely reading off the part number, so a new sensor arrives, gets fitted, running improves hugely, and only after a year and all this delving and enquiring does a glimmer of light get through suggesting that the matter goes deeper than simply replacing a component. By the way, the fitting bracket on my friend's car is identical to mine, so superficially the two cars are the same.

So now what I need, people, is a part number for a five-contact AMM (or MAF sensor as the Parts Manager referred to it). Any takers??

[Stephen Edwin]

Sorry Angie I haven't been brave enough to disconnect my Air Mass Meter to count the pins yet, in case I disturb the electrical contacts.

( I'm really not yet convinced by this pin counting method of selection. Has anyone else had problems re the number of pins? It sounds as if your local dealer has only one part number for the component for your car, does that part number come up on their system for all models with same LH 2.4 system? In your shoes I'd like to know what is going on before spending more money.)

*****

I'm slightly lost, is the car running well since you last fitted your existing Air Mass Meter?

*****

Same sort of point from me, yes again. So.

• How long did the car run well with the Air Mass Meter you bought from Braydons? Does that indicate that the Air Mass Meter is OK in itself?
• And how much does it cost to clean up the contacts including the earth bracket and see what happens, compared to buying another Air Mass Meter?
• And how much would a diagnostic test cost?

And the Bosch service centre might advise by telephone about that 5 pin 6 pin issue and about part numbers?

*****

Clifford, Re the support bracket, yes mine has rubber between the bracket and the Air Mass Meter. But is that cushioning rather than electrical insulation? Does the earth connection go through the thread of the machine screw in to the Air Mass Meter?

[Angie]

[QUOTE=Stephen Edwin;2164402]

*****

I'm slightly lost, is the car running well since you last fitted your existing Air Mass Meter?

QUOTE]

Sorry, should have explained. In both cases when the sensor's been replaced the car has run better, this time, with the sensor from my friend's car, even better than before, as far as smoothness under power is concerned, never misses a beat. But - the idling is awful, up to 2,000+rpm sometimes then dropping back to under 1,000. Never really predictable either, makes driving slowly in traffic uncomfortable at times. Sometimes almost cuts out too, momentarily. This leads me to think that the matter of the contacts really is relevant because the sixth contact is probably associated with idling, but of course as my connector only has five contacts/wires the signal isn't being transmitted.

I've emailed the parts department with the part number I bought last year so that they can check it against their information. I still keep coming back too to the wiring diagrams which consistently show only five contacts.

The rubber grommets on the bracket are, I feel sure, an anti-vibration device. The sensor is earthed from contact no. 1 regardless of the number of contacts.

I'm not going to invest in a new sensor until I'm as sure as can be that I've had the incorrect component all these years.

If no other information is available from whatever source I will bite the bullet and go down to Volvo for a diagnostic, which will cost around £70 apparently. Could be money well spent I know, but I want to make sure the obvious faults are attended to first, I've spent very little so far, thank goodness.

[Clifford Pope]

Are you sure it's not another, intermittent fault, confusing the AMM problems?

Coincidentally, the next time I drove my car after reading your latest poor idling post, mine did the same thing. Idling was anything from 1500 to 2000 rpm, wavered about, sometimes would idle properly, sometimes touching the accelerator sent it off high again.

I know from past experience exactly what causes it - the Idle Air Valve shutter needs cleaning again. It does this about once a year. A squirt of WD40, a brush with a fine paint brush, turning the rotor with the wooden end of the brush, another blast of WD40 followed by blowing through it, and it works perfectly again.
Much more infrequently, it's the throttle body and dirt build-up on the butterfly, causing an uneven air flow.
Just a thought.

[Angie]

Thanks for that, Clifford, it's quite possible that there's more going on than just the MAF sensor, but it still remains that there's a mis-match between connector and contacts, so I really do need to resolve that.

The throttle body was cleaned a few weeks ago and that certainly improved things. The idle valve is fairly new, bought around the same time as the MAF sensor, but maybe I could get it cleaned next time the car's in the garage, it's not something I'd like to undertake - I can fit and remove these components but fiddling about with them is a bit more daunting!

I'll get to the bottom of all this eventually and the help and suggestions here are really useful.

[Stephen Edwin]

Angie, is there definitely a pin mismatch? Has anyone got a 240 with a 6 pin connector? And consider Clifford's earlier post:

Originally Posted by Clifford Pope

According to my Haynes the LH2.2 has a 6-pin and the LH2.4 a 5-pin.

But I have just had a look at my two spare AMMs and the one on the car, all from LH2.4, and they all have 6 pins.

If you plug a 5-pin connector onto a 6-pin AMM then obviously one of the two end pins can't go anywhere. According to the diagram one end pin connects to the system relay, so surely that is the important one - apparently the engine works quite well with that mismatch.
But the other end pin (black wire in the connector, numbered 36) on a 6-pin AMM goes only to earth. Perhaps it doesn't matter whether the AMM is earthed or not, so that is why it still works?

And from that post, I don't know why you are sure your Air Mass Meter is earthed via the connector? Perhaps does a multimeter on the ohms scale show that one of the connector pins goes to bodywork earth?

Me, I would clean up the connector pins and the machine screw including its thread that might actually be the earth connection. Possible fit an earth strap or a length of insulated wire from that machine screw to a good known earth point. Cleaning all of that and fitting an earth lead is cheap and can surely do no harm?

Me, I'd go for diagnostic testing providing they can offer something of a serious investigation. It must be worth a "frank discussion" with some Volvo dealer[s] and that Boasch service centre not far frm you. See what each of them can actually offer. Do they have information as to what the correct components are? Will components be tested? Can they detect connection problems? What can they do and how much do each of them charge?

What you don't want is an unexpected possibly large bill for additional testing so I would ask about whether there might be a need for further testing.

Clifford, I'm lost re the components you have just mentioned. If those exist on my B200F I shall have to learn about them and about cleaning them, one day.

[Angie]

I was relying on the wiring diagram, clearly shows contact no.1 to earth, the other four to ECU. You're quite right, though, Stephen, I really do need to find out what's fitted on other cars of similar age.

I did have a chat with the Volvo service manager - surprisingly they still get quite a few 200s in so he seemed to know what he was talking about, which is why he suggested other checks for the garage to carry out before spending money on a diagnostic.

I'm still bothered by this number-of-contacts thing, as when my friend bought his sensor, from the same dealer two or three years ago he was asked if he needed a five-contact or six. At that time they happened to have one in stock, six contacts as required, guess it was old stock, as Bosch, made in Germany. It was that which set my 'liddle grey cells' working! My connector definitely has only five contacts and five wires, it's not been modified or anything, so therein lies the mystery. Just to recap, Haynes diagram '1986-on' shows six wires, no.1 to earth. The more detailed and much clearer diagrams on the link I posted consistently show five for every year from 1989 to 1993, the only different one being four contacts for LH 3.1.

My head hurts!!

[tannachyallen]

Originally Posted by Angie

......much clearer diagrams on the link I posted consistently show five for every year from 1989 to 1993, the only different one being four contacts for LH 3.1..........

My car is a '91' and has 6=6 contacts.........

Dave A

[Stephen Edwin]

Angie, just in case you decide to test with a multimeter, I'm sure you know this, before using the Ohm Scale disconnect the car battery or you could wreck the multimeter. Sorry I forgot to mention that. ANd of course before disconnecting the car battery, be sure you have the radio code if one is needed.

It would be interesting to know about the unspecified "other tests" as opposed to the unspecified "diagnostic". I would still be wanting frank discussions including also with that Bosch service centre.

tannachyallen, that's interesting. A 6 pin cable and on a car within the Haynes age range for 5 pin.

Anyways re myself Angie I'm at or beyond the limit of my little learning. I doubt if I can contribute much more. Sorry.