91 740 Wagon (940 body) - MAF (air flow meter) check

goldmember · Post by **goldmember** » 05 May 2008, 00:42

Hello

Is there any way to check if the MAF is working? I am having an intermittent spluttering (go to accelerate and the car goes nowhere and nearly stalls & sounds like its starving of fuel) problem. The lamda light comes on. I check the codes and it says its the MAF. The spluttering stops, the light stays on until it happens again. I reset the diagnostic unit and the lamda light disappears but the problem returns in about a month.

Upon checking the MAF, I'm getting a regular 1.38V out of it (I think the spec. should be 1.4V, but the difference could be in my multimeter). I tap the MAF with the meter on it, without any change in voltage at all.

The other question I have is, can I just supply a permanent 1.4V to the computer and bypass the MAF alltogether? Would it affect cold starting or performance on really hot days? This may be an easier fix than forking out at least $100 on an aftermarket or refurbished MAF.

Cheers

George

anbran · Post by **anbran** » 05 May 2008, 07:45

I'm not sure that this is the proper way to diagnose, but I had the same problem with sputtering, etc. I would unhook the wire connection to the MAF and noticed that nothing would happen. As soon as I re-connected it, the engine stalled.

I did this a few times to be sure and then called a few Volvo mechanics. They usually said that the MAF is faulty.

I had been having the problem, on and off, for months...every 50 or so kilometres. Drove me nuts!

Anyway, I finally replaced the MAF with a brand new one from FCP over 4000 km ago...

Its been running great since! (not even a slight hesitation or anything.)

Hope this helps!

goldmember · Post by **goldmember** » 16 May 2008, 17:57

OK (BTW mileage is just shy of 215000 km.)

I changed the MAF. I did it while the car was running to see what would happen when the old one was disconnected (started running lumpy) and then fitted the new one (while still running - lumpy) and the revs went up a little then came down the right level and stabilised.

This would indicate to me that the new MAF is working.

The problem I have now is that whenever the car is started, it is very lumpy with it sounding like it is about to conk out but stabilises after about 20-30 seconds. With the old MAF, it did not do this.

I reset the computer and it still did it.

Last night I disconnected the negative terminal for the whole nitght (as I read on someone else's post here) and this morning it still does it.

Also, I don't feel it is running as good as it used to. It is an aftermarket MAF I purchased from partsdome UK, via Ebay.
Any ideas?

cheers

George

Post by **billofdurham** » 17 May 2008, 12:30

When you checked the codes did you get 1-2-1?

That is the MAF but could also be the main fuel relay. On checking with a multimeter my books say the voltage at the MAF should be 12volts.

The attachment describes how to check both the MAF and the main relay which is in the fuse/relay block at position E.

Bill.

goldmember · Post by **goldmember** » 17 May 2008, 14:10

Hi Bill

Thanks for your reply.

The only code I was getting was 3-2-2. I reset the computer and it didn't take long for the code to return.

After taking the car out last night and stalling a couple of times, the lamda light is back on. The new codes are: 1-2-1, 2-3-2 & 3-2-2.

You mention an attachment, I can't see it, how do I access it?

I have a couple of voltage checks between ground & the output (terminal3) and they should be 1.4V DC & 2.3V DC for iginition on (only) & idle respectively. I'll check these and get back to you.

Regards

George

Post by **billofdurham** » 17 May 2008, 15:28

Sorry George, I forgot to attach the attachment. There is something about memory loss as one gets older but I can't remember what it is.........

Attachment:

Code 2-3-2 is Lambda adjustment - Check intake manifold and fuel pressure.

3-2-2 is Air flow meter hot wire - Check the airflow meter which you have already done. Suggest you check the relay.

Bill.

goldmember · Post by **goldmember** » 18 May 2008, 03:12

Hi Bill

thanks for the attachment.

The new Air Mass Meter does not work. I did the simplest check first. While the car was running (like crap), I disconnected the plug and it made no difference.

I also checked for the output voltage and it was a few millivolts instead of 1.4V with the ignition key turned (but motor not running).

I put in the old air mass meter and the car ran OK again. I cleared the codes and it has been OK since. (but I still have not solved the original intermittent car running like crap problem and then getting the 1-2-1 code ).

I emailed Partsdome (with a nice email) for a refund, I'll let you know how it goes.

Has anyone else had intermittent problems like this and found it was the air mass meter (other than Anbran)?

I am getting 12V DC between pints 1 (ground) & 5, so the imput signal seams to be OK. As an asside, I took some resistance readings between the terminals on the unit and compared it to the original one I have. Resistance on the original Bosch unit between pins 2 & 4 and 2 & 5 is about 20kOhms. On the new unit (which is cactus) the reading is only 2kohm.

My suspicion is that the cheap unit that I purchased from Partsdome (I knew it was not an original from the start) did not last the burn off phase, (when the engine is turned off). This is why it gave me the code of only 3-2-2 to start with. Then, on the 2nd use, the burn of phase destroyed the meter totally. The little wires are still in tact although they are not nice and taught like the original Bosch unit. They seem not to be pulled tight. I did notice this though before I even used it and was not as a result of whatever happened in the car.

I'll keep you posted how I go.

Cheers

George

Post by **billofdurham** » 18 May 2008, 12:08

It certainly sounds as though you have a dud new sensor. Hope you get a refund.

The original 1-2-1 problem could have been caused by the main fuel relay starting to go bad. They can cause intermittent problems for quite some time before dying.

Bill.

goldmember · Post by **goldmember** » 18 May 2008, 13:57

I just received a refund from Partsdome. Very impressed!!

Bill, can you please advise where to find the main fuel relay?

Cheers

George

Post by **billofdurham** » 18 May 2008, 15:28

Very fast for a refund. With that sort of service they are worth patronising.

Main fuel relay is at position E on the main fuse/relay panel, centre of dash under the dentre console. See attached (must remember to attach it):

My memory has improved!!

Bill.