My 1998 V70 AWD has been reporting an error code of P0107 for some time now. The generic explanation of this code is MAP sensor reading low. As this car does not have a Manifold Absolute Pressure sensor, I am assuming the problem is some other fuel metering/intake problem. Does this sound right? When the code first showed up, there was no noticable problem with the car. Recently it started stalling when coasting to a stop, but restarted fine and seemed to have a steady idle. Just once or twice it stumbled on the highway. Then one day it was running rough, stalled at some trafic lights, then would only run a few yards and stall again. I took it to an independent mechanic (I have no previous experience with him) who insists the problem is the sensor that Volvo calls a MAP sensor, which is actually an accelerometer bolted to the front right fender used to pick up road noise (cancels the road noise for the knock sensors). This doesn't sound right to me. Any group wisdom here?

In the "may be related" area: Oil has been pooling on top of the cylinder head and appears to be coming from the oil filler cap (also leaking around distributor). While looking for a leak in the intake system (for the CEL problem) I found the rubber elbow between the inlet maniflod nipple (next to the power steering pump) and the small vacuum hose to the PCV tree (just downstream of the MAF sensor), was all squishy and collapsed (but apparently not leaking air into the manifold). Am I right in thinking this could cause the PCV system to stop venting and cause oil vapour to blow past the filler cap? I plan on replacing the whole PCV system at this point, as I have lots of bits off already.

Any chance these two issues are linked?

Any help appreciated.

 

They might be but not sure.

The Map Sensor is really the Mass flow sensor mounted in the Air box.

The hose you found collapsed you can bypass the intake end and run it differently.
Cap the side of the intake. Then run the Hose from the turbo induction hose to the manifold. You will have to cut the stock hose at the Plastic part of the hose and keep the elbow. They are 2 different sizes. The elbow on the induction pipe is bigger at the hose. So keep a couple inches of the plastic hose and run a rubber one up to the Vaccum tree and you are set.

 

That's a very tempting idea (moving the vacuum source for the PCV to the "T"). I was planning on replacing all the PCV system, but it is a big job and I don't really want to take the inlet manifold off. I think I will give that a try.

With respect to the MAF sensor: There are codes specific to the MAF sensor and I am not getting them. Do you think the MAF sensor is out of spec (thus causing the P0107 code) but not broken enough to cause a MAF error code? If so, I assume the only way to find out is to replace the MAF sensor?

When I talked to the parts guy at FCP Groton, he said he had not heard of a case where replacing the road noise accelerometer (which Volvo calls a MAP) fixed anything. However, he said there was a barometric pressure sensor (presumably to measure ambient atmospheric pressure) that sometimes caused problems. I can't find such a device in the manuals or in the car. Any idea where it is, what it does, and if it could be the problem?

Just out of interest, on these lite pressure turbo cars, what is the maximum boost seen? Does the pressure in the inlet manifold go possative (above atmospheric)?

Thanks for the help.

 

It is possible about starting to go bad.


The Baro sensor would be located just in front of the washer fluid fill.
It is mounted to a bracket. Like next to the hood latch.

Max Boost is I believe like 10 to 12.

 

Thanks for the location of the barometric pressure sensor. This is the part the mechanic was pointing at and saying was bad, but he kept calling it a MAP sensor. He also quoted me a price for the part that was consistent with the price of the sensor Volvo calls the MAP sensor (vertical acceleration sensor), over $400 (ouch!!).
I can see how the barometric pressure sensor (AKA altitude sensor?) could cause this error code, so I think he may have diagnosed the right part, but he is getting confused about the name and was ordering the wrong part.

 

$400.00 must be another part then.

 

Thought I'd just give an update.
First, thanks for all the help. It's great to have people that have "been there, done that" giving you the benefit of their experience.

So in the end I decided to do a complete PCV system replacement: New oil trap and all hoses (except the big MAF to turbo hose) and clamps. Also new oil filler cap seal.
Replaced the altitude (barometric pressure) sensor.
New plugs, plug wires, distributor cap, rotor, air filter.
Thorough clean of throttle body.

I have done about 25 miles since completion and no codes have shown up yet, but I still have a couple of problems.

First, I still have the problem that the car stalls when slowing to a stop, or when idleing. It doesn't splutter and die, it will be idleing OK and then just die like I turned it off. Running the AC seems to make it worse.

Second, if I pull the oil dip stick with the engine hot and running (or remove the oil filler cap), I get the puffing smoke you would expect if the PCV system was blocked. But of course it's all new!!! Don't know if that's causing an oil leak yet (like it was before), I have not driven far enough to tell.

I plan on removing and cleaning the idle control valve tonight, but I'm not too optimistic.

 

Maybe also a bad Cam sensor.
It doesn't act like it is running out of Gas does it?

 

"Maybe also a bad Cam sensor.
It doesn't act like it is running out of Gas does it?"

I did remove/clean/check the idle air valve and it looks and works fine. When I test drove the car to see if the cleaning had improved things, I didn't get out of the driveway before it stalled, so, no improvement.

For the next few trips I modified my driving technique. When slowing down or stopped, keep right foot on gas and brake with left foot. By keeping the rpm around 1000 I had no stalling. Today I drove normally (no keeping the revs up when stopped) and had the AC on and it seems to be idling fine. Guess I'll just wait until the symptoms return.

I did have a couple of questions arising from my recent work on the intake manifold:

First, when I was doing the PCV system replacement, I pulled the fuel rail complete with injectors from the intake manifold. I ordered new seal from FCT for reassembly. What I got were the blue seals about one inch in diameter and resembling a lipped oil seal. When I look in the Haynes manual and at pictures on line, I see these seals installed in the first, larger counter bore in the intake manifold. However, there were no such seals installed on my car. My injectors have a small (maybe 1/4" or 3/8" diameter) regular black rubber "O" ring in a groove right at the very tip of the injector. This pushes into the second, smaller counter bore in the intake manifold. When I contacted FCT they said they only had one seal listed. It looked as though my injectors had a groove where the big blue injector seals would sit and therefore would not have sealed there anyway if I had tried to use them. The pictures show black (or dark blue) injectors, while mine are red. Any idea what is going on here and what I should have installed? I ended up putting it back with the old seals as I did not have new ones available.

Second, while I had everything apart, I tried to check as many components in the vacuum lines as I could using a small hand operated vacuum pump. The only thing I found that was suspect was one of the check valves in the evap cannister purge plumbing. There are two, the suspect one is in the pipe that goes to the intake manifold. When I checked it, the flow in the direction of the arrow (toward the intake manifold) was wide open. In the other direction (which I assume should be completely sealed?) I got a reduced flow, but not a seal. When I tried to buy a replacement I was told I had to buy the complete hose assembly for $60 so I declined and replaced the old one. Any thoughts on how critical this is and whether it's worth replacing?

 

Well I finally fixed the stalling problem by replacing the Air Mass Meter. I first tried cleaning it and that made things worse.

Thanks for all the help here.