what is a map sensor

[jblackburn]

Mass AIRFLOW sensor is in the tube coming out of the air filter box and down to the turbocharger or into the engine, depending on which model.

The one picture above is a barometric pressure sensor - just there to sense change in elevation. The mass airflow sensor measures the amount of air sucked in by the engine, and adjusts fuel mixture accordingly.

If you're getting a code for the Manifold Atmospheric PRESSURE sensor, it has nothing to do with the airflow sensor.

[smarzig]

staurt any luck on your end? your symptoms and mine are literally exactly the same except mine occurred after a garage change my serpentine belt and AC compressor and pulley.

[stuartg3]

Smarzig,

no luck yet on my end - although I haven't spent much time yet. I had my wife take the car to the local auto parts to have the codes checked. As suspected, there were no codes to be read (there is no check engine light). Evidently the car doesn't realize that it's messed up!

I did verify that the timing belt looks great (was changed out not long ago) and the timing marks seem to be lining up correctly (that was a big concern given that the engine is an interference engine).

Based on some advice I have gotten, the next few things that I am going to check will be the plugs (visual inspection and maybe replacement just because) - I haven't checked the records to see when (if) they have been changed. Next I will clean the throttle body and look at/clean the MAF sensor. Wish I could follow jda2000's advice and swap out the MAF with another volvo owner.

I'm still looking for an answer as to whether anybody knows how to verify if the coils are bad/weak? Read about a guy that had similar symptoms (on another forum) that ended up replacing 2 coils to solve his problem. I'm also guessing that my non-turbo car has a MAP sensor also?

[stuartg3]

Okay, so the latest update on my wife's '03 V70 is that I have changed the plugs (they were due for changing although they didn't look too bad), I looked at the MAF sensor (looked fine - but dirty) and cleaned the MAF sensor, and I cleaned the throttle body.

I had high hopes, but there was no difference in the way the car drove. I now have some techron fuel system cleaner in the car. I'm not sure if it's wishful thinking but maybe it's getter a little better. I guess the most significant symptom is that the car acts like a carbureted car when you floor the engine from idle and the old carburetor would dump too much fuel and flood the engine. I'm thinking (hoping) that this is clogged fuel injectors putting liquid (instead of atomized) fuel into the cylinders. I'll post back after we run this tank through the car and let you know if any of this helps.

[jblackburn]

Stuart, wouldn't hurt to change the fuel filter as well just to eliminate things. I'd say this is either a bad sensor (MAF) or some kind of leak somewhere. The MAP sensor won't rob you of power; in fact, it doesn't really do anything.

Follow behind the car and have her stomp the pedal. Do you notice black smoke out the tailpipe?

[stuartg3]

okay, the fuel injector cleaner doesn't seem to be working. I have run most of it through the engine and still no change. I thought I knew where the fuel filter was located (based on a post I read on this or another forum) but I couldn't find the filter tonight. Does anyone know where to look? I thought it was in front of the rear wheel on the passenger side of the vehicle. I found what may be the fuel pump - located above the rear sub-frame. It was a rectangular sort of thing. I'm not sure how you would get to it without removing the rear sub-frame (unless you access it from the top from an access hole in the car). I don't think the filter was up there, but I was using a poor light in the dark.

I wasn't able to check for black smoke - what would that tell me? BTW, the catalytic converter was not too hot (I was told that a plugged cat would be very hot) and the other thing I verified was that there is a second O2 sensor at the cat. Based on what I have been told, I feel fairly sure that I don't have a bad cat because I would be seeing an error code from that sensor.

[jblackburn]

Black smoke coupled with trouble accelerating means that the engine is dumping too much fuel into itself and choking on it.

I had a Buick that had the mass airflow sensor go bad, and it would buck and shudder at partial throttle, but if you floored it and got the revs on up, it would pull smooth as butter. The Volvo, on the other hand, just fell flat on its face and wouldn't even run - smoked like a diesel too.

You can unplug the airflow sensor and try running the car - you will set a check engine light for sure, but it should go into limp mode without it and run on a 'best guess' estimate. Don't go around gunning it too much in that condition, but that should let you see if it will still hesitate at low RPM and/or rev above 4500 without choking. The sensors can (and do) go bad frequently without setting codes.

[stuartg3]

I unplugged the MAF and there was a short stutter of the idle and then the car smoothed out. When I drove the car there was no difference. The hesitation off of idle and the surging at higher rpm were still there.

[jda2000]

stuartg3,

the car should not run equal or better with the MAF unplugged. It should run worst since you are disconnecting a good part.
This indicates your MAF needs replacing.

[smarzig]

I'm now dying to know what the heck the thing is since i have this exact same issue.
When my serp belt snapped,on the way to mechanic, i was able to accelerate as much as I wanted If i recall correctly even through I had
no power steering. That sure isnt the case after belt and AC Comp/pulley replace.

One final note, things did get a little better because before i would step on the pedal and the engine/car didnt respond at all, but not after the battery reset/tap on the break the engine at least will rev accordingly but wont accelerate. Shifting is perfect.