98 V70XC MAF Voltage Help

dmcfan · Post by **dmcfan** » 15 Jun 2015, 14:49

Perhaps it is the mobile site but I cannot find the how to topic on how to test the MAF with a multimeter and what to look for.

Post by **abscate** » 15 Jun 2015, 15:41

A quicker test is to turn engine off, disconnect the electrical plug from the MAF, and start the car up and see if it runs better. What are your symptoms leading you to think the MAF is faulty?

dmcfan · Post by **dmcfan** » 15 Jun 2015, 15:55

I have had what has felt like a random misfire for a few months now that eventually turned into a few hundred rpm drop at idle after driving then sluggish off the line after the rpm drop. No codes so I figured time to do the full tune up. I replaced the plugs, wires, cap, rotor, fuel filter, air filter with the kit from FCP. The parts were definitely needed and it ran much better after it was all done.

After a few days of not having the stalling symptoms they came back along with the p0171 code. This is the only code coming up. I have seen a lot of posts with that code being accompanied by others but that is not in my case.

So Saturday I used MAF cleaner and did seafoam in the intake only and cleared the code. The car ran much better and was problem free until this morning and the stumbling is back along with the CEL.

dmcfan · Post by **dmcfan** » 15 Jun 2015, 16:32

Also sometimes when accelerating the car feels like it hits a wall and the rpms stick and hold then goes back to normal.

Post by **jimmy57** » 15 Jun 2015, 17:15

Before you spend much time and money try this:
disconnect the MAF connector
Spray WD-40 into the connector and plug it in and unplug 5-6 times
Spray the connector again and then shake the WD-40 out of the connector
Plug the connector back onto the MAF
Use a cable tie and secure the cable to the MAF body. Loop the harness back by the MAF body, it is long enough.

The MAF connector and pins "fret" from wiggling and the reistance build up and make for a bad connection that affects the MAF signal by a few millivolts. That is plenty enough to cuase driveability problems.
This was a service bulletin for these cars 14 years ago when they were relatively new.

dmcfan · Post by **dmcfan** » 15 Jun 2015, 18:56

Could you elaborate more about "loop the harness back by the MAF body"?

dmcfan · Post by **dmcfan** » 15 Jun 2015, 22:03

Found the full tab. I will give it a try but not having high hopes as it just doesn't seem like that would fix these issues but who knows. I am just hoping it isn't the fuel pump given the amount of work needed to replace on the XC.

Post by **abscate** » 16 Jun 2015, 00:53

A P0171 code is often caused by a vacuum leak. Get a scanner with real time data and see if your MAF is putting out a good air flow reading to diagnose. It's cheaper to buy the scanner than the MAF or pay to have it scanned.

dmcfan · Post by **dmcfan** » 16 Jun 2015, 02:46

Any recommendations on scanners? Since mine is a 98 I want to make sure it can also reset my service light.

For the vacuum leak it would probably be best to get a smoke test then?

Post by **jimmy57** » 16 Jun 2015, 05:57

The connection problem lowers signal voltage, lower signal voltage means ECM computes a shorter injector fueling time per cycle which leans the mixture. Volvo produced the bulletin that instructed tying the cable to the MAF body as shown in photo mf2 attached to address MAF connector causing intermittent stumble, erratic idle, and codes related to fuel mixture.
If the MAF connector is the issue then wiggling the connector while engine is running may make engine rougher or misfire.
As I said this may not be it. You listed that it ran better after MAF cleaning. When you cleaned MAF you unplugged it or at least the connection got moved. This might have changed the connection temporarily. A cable tie is a few cents and then you drive it to see if it is OK or not.
I found reference to the bulletin: http://workshop-manuals.com/volvo/v70_g ... tor_loose/