Has anyone seen a MAP sensor fail on a 6.0? I have some data that seems abnormal.

At idle in neutral = 14.32
At 2500rpm in neutral= 14.14

At idle in drive = 14.46
At 1725rpm in drive = 21.68 (loaded, not moving)

The funny (odd) reading was the Turbo>

in drive at idle the duty cycle was 64.27
in drive at 1725rpm = 55.97
in neutral at idle = 65.03
in neutral at 2500rpm = 45.00

I'm tinking I hgave a bad MAP sensor, has anyone ever seen one go bad on the 6.0?

 

What about the data do you think is abnormal? Remember that it is an absolute pressure sensor. This means it is measuring atmospheric pressure in addition to pressure in the manifold. To know boost pressure, you subtract the BARO sensor value from the MAP value.

 

my thoughts are that the manifold absolute pressure should go up under load, especially given that it is a forced air system (turbo). Am I mis understanding the process?

 

It should. And if I'm reading these right, it did.

The only condition you posted there that consisted of a load was the last one, and the MAP pressure rose by 7 PSI.

 

yes, however the max pressure reading is about 75 psi? And for it to only raise 7psi seems a bit odd? Under loaded condition I have a lot of blue smoke and it has a very strong smell of deisel. My truck does not make black smoke, ever. Also, while under load (driving) the truck seems to boost and then stop boosting and then bosst and then stop, all in a short ime frame. It begins stumbling (shuttering) once it hit overdrive and if I kick it out of overdrive the shuttering stops. it has gotten worse over the last day. The only thing I did was to change the oil, this time I used 15-40? weight oil in lieu of the synthetic. Starts are a bit slower as well, meaning that it doesn't fire right off like it did when I had synthetic oil in it. I'm baffled and simply looing for a solution to this mad equation! lol

 

Boost should never really go above the mid 20's. The boost you show under the load you describe sound normal.

Your problem could be a failing FICM. You can check FICM voltage, but even if it is OK the FICM could still be failing. You might also look at your Injector Control Pressure. If it is low I think it might cause the problems you're describing.

 

I did do that. FICM is constantly at 48.5 volts. Pressure desired is most always within a few pounds of actual pressure. there is a rae occasion where the pressure desired is a bit higher or vice versa, but it is never for more than a second or 2. i replaced the ICP, IPR and HPOP just about a year ago.

 

You could still have a failing FICM. I don't know how you would diagnose it further. Also, blue smoke is a sign of burning oil. It's possible your turbo seal has started to fail and is dumping engine oil in the intake or the exhaust.

 

I thought about that as well but it doesn't seem to be losing oil, or coolant for that matter. I gotta turn in for the night but if oyu have any further thoughts or if anyone else does, please post and I'll check in th emorning. Thanks for your input, as I'm simply stumped right now! The truck does have about 205k on it, so I can't blame it for being tired, but I sure do wish it would just throw a red flag up from the part(s) that is or are failing! LOL... wouldn't that be nice!

 

How much oil did you put in?
check the oil level after it sits overnight.

Perhaps you over-filled the oil?
If you didn't remove the oil filter, it doesn't take as much oil to re-fill???

 

changed the filter and installed 15 quarts

 

If you suspect that the MAP sensor is causing a delay in boost, follow the boost line back to the manifold, remove the fitting and check for carbon buildup in there.
If it were a problem with the MAP sensor itself,one would think it would throw a code of some sort.
Also since you changed oil it could be injector stiction. Those injectors really like the 5w 40 at startup.

 

I actually get a surging boost when accelerating hard. Like something is sticking. It will boost then flat then boost then flat then boost. All of this happens very rapidly. The shuttering when it drops into overdrive is the worst of the problems, I just have to think they are connected. It also sometimes takes more foot feed than normal to get it to kick out of overdrive.

 

Have you checked your EGR valve? The MAP sensor seems to be functioning properly. Stuttering/shuddering is more like an ICP problem, but the EGR valve is a quick and easy check to start with. It's also possible you have a sticky turbo. Has it ever been cleaned?

 

never has been cleaned. the EGR was replaced and left unplugged over a year ago. I cleared all codes and drove the truck to work. Shuddering continued only after in overdrive and ascending slight hills. Truck idles fine though. NOW I have received code p0500 on the OTC. Also the truck doesn't seem to have the pull it used to have. 208k miles now. I know I shuold try cleaning the turbo, I'll get the kit this week. What about a possible plugged (partially) cat?