Ask a Car Mechanic and Get Answers to Your Car Questions ASAP
Is that nipple exposed or inserted into the intake? Here is more testing info on the MAP, let me know about that vacuum nipple.
The Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure, which result from engine load and speed changes. The pressure measured by the MAP sensor is the difference betcovered in this guideen barometric pressure (outside air) and manifold pressure (vacuum). A closed throttle engine coastdown would produce a relatively low MAP value (approximately 20-35 kPa), while wide-open throttle would produce a high value (100 kPa). This high value is produced when the pressure inside the manifold is the same as outside the manifold, and 100% of outside air (or 100 kPa) is being measured. This MAP output is the opposite of what you would measure on a vacuum gauge. The use of this sensor also allows the PCM to adjust automatically for different altitude.
The PCM sends a 5 volt reference signal to the MAP sensor. As the MAP changes, the electrical resistance of the sensor also changes. By monitoring the sensor output voltage, the PCM can determine the manifold pressure. A higher pressure, locovered in this guider vacuum (high voltage) requires more fuel, while a locovered in this guider pressure, higher vacuum (low voltage) requires less fuel. The PCM uses the MAP sensor to control fuel delivery and ignition timing. A failure in the MAP sensor circuit should set a Code.
The MAP sensor voltage reading is the opposite of a vacuum gauge reading. When manifold pressure is high, the MAP sensor value is high, and vacuum is low.
MAP sensor specifications-note how altitude and pressure affect the voltage readingsREMOVAL & INSTALLATION
OK so the nipple can mount into the manifold directly? One way or the other that nipple has to be connected to the manifold.
It is still about 105-110ish. Looks like this week is going to be humid-I'm not far from you, I'm in Vegas. The more troubles the rest of the country has I don't know why anyone would not want to live in the southwest. The heat more than make up for the lack of natural disasters-dont you agree?
Let me know what you find out with your map sensor. When you do get it mounted to vacuum, clear the codes and see what happens. I'm sure this is your problem.
Thanks for using JA
Yes...I agree...extreme heat beats hurricanes anyday!
There is nothing readily apparent, that connects directly onto the nipple. As I said, I spun it around (nipple facing downward, as in the illustration you sent), snapped it back into it's plastic harness, sealed up the manifold cover and headed out for a test ride, after clearing the history from the diag. display. After about 15 minutes of driving highway and local, there were no problems, but...this has happened before, only to have it re-appear a couple days down the road. I remain cautiosly optimistic.
One last thing re: the MAP sensor connector (nipple). You stated it has to be connected to the manifold somehow, yet, as I previously stated, there wasn't anything readily visible, for the nipple to connect into. If you think it would be helpful, I could remove the cover again and snap a couple shots of the connector, with the sensor snapped in and with it removed.
Let me know,
The pictures displayed OK. When the map sensor is installed in its holder like that the nipple should be connected to the manifold with a grommett. What I dont understand is how if it has been unhooked all this time, that should have been a huge vacuum leak. Check it out and let me know what you see.
no grommet to be found. is the grommet supposed to be attached to something, like a vac. hose, like you previusly referenced? I also pulled up the fuel rail cover that surrounds the perimeter of the manifold and had a look underneath for anything that looked like it belonged attached to the nipple, but found nothing. Is there a way for you to confirm that something is supposed to be attached to the nipple?
I just posted but it disappeared.
What I said was, there is definitely a port there, I can see that it is a direct port not a vacuum line connection. The port must be clogged up with carbon, that would explain why there is not manifold vacuum loss without the map installed.
Access your diagnostic mode and scroll through the ECM data until you see the MAP. Observe the MAP readings while driving and let me know what it says.
I just returned from another test drive and the damn thing stalled again! The old p032 and p095 are back and I just made an appointment with the local shop in town that last attempted to service this issue back in Feb, unsuccessfully. Are you aware of anyone here in Havasu that could make this problem go away?
What shop did you have it at? I know exactly what is wrong with it now, we just have to find someone competent to listen to what it is and fix it. That might be easier said than done.
Are you in today? Sure would like to click the accept button in exchange for resolution to this issue!
I beleive that your port for the map sensor in the intake is probably carboned up and plugged. I don't know of any other explanation as to how it could be running either-the vacuum port has got to be pluggd up, and the sensor has just been running in default mode.
Do you understand why the map has to be connected to manifold vacuum?. The way it has been running, the sensor has not actually been reading anything. The wires are just ground, 5v reference, and signal to the ECM, the signal however is from the pressure reading from the manifold.
Ask him about the port that it goes into-I would have my doubts too. So you went and talked to him and he said he was going to take care of it today or tomorrow? I would not pay him any more money-that is a pretty basic concept-that the map sensor has to be connected by vacuum to the manifold-hence the name manifold absolute pressure sensor! If the port was not totally plugged up the mistake couldnt even have been made because the vacuumm leak would be so bad it wouldnt run right anyway.
When you do get it resolved, make sure that the battery gets unhooked for at least 20 minutes to clear the capacitors out. The computer builds a kind of database while the engine is running and it is going to be completely out of whack becuase of running that way for so long. What has happened is the computer has substituted values or just recalibrated everything else around the fact that there is no manifold pressure data, so it needs to be completely cleared to start the fuel trim tables over again.
Let me know how it goes. I can't wait to hear what he has to say about the vacuum port! I should be in on and off all day so I'll watch for your post.
I'm going to drop off the car this afternoon and hope for the best.
While the cover was still removed yesterday, I scrutinized what was underneath the sensor's mount. All I could see was the throttle body, off to the rioght, in the picture I sent you. I cleaned that with carb cleaner a few months ago, but...it didn't appear dirty at that time. Aside from that, there was no visual evidence of any "port" that you made reference to. Regardless, I'll bring him a copy of your comments, after editing out the payment references. ;)
More to come...
hi...just got the car back and they guy said he replaced the MAP sensor and that he couldn't get the car to act-up. Because of your replies, you made me realize the MAP sensor was installed upside-down, which was a major discovery. Although your references to it being installed directly into a "port" remain ambiguous at best (could not find any sort of port that fits your description), I feel that you at least are entitled to the $9.00 for your efforts.
Have a nice extended weekend in the 100-teens! I know I will!
OK there is nothing ambiguous about the fact that a MAP sensor has to be hooked to manifold vacuum to be functioning. I find it very amazing that a so-called professional technician is unaware of this fact. I think this is illustrated by the fact that he gets a zero reading and thinks the sensor must be replaced every time he checks the car.
For some reason, I cannot find a picture of the pre-1996 northstar map sensor anywhere, including in GM electronic service information. I did however, take the cover off a friends 1996 Northstar just to show you that I am not crazy. This MAP sensor is a little different style than yours but if you look at the picture you will see the port I was referring to that the sensor fits into.
I have figured out that on your car you are missing a vacuum line connection form the gold colored nipple close to the map sensor bracket to the sensor. The port is probably clogged up due to carbon so there is no leak.
I appreciate you accepting but I do not want to end this session with you thinking that there is not supposed to be vacuum to the MAP sensor. I dont care if you change it every week forever you will not get rid of that code until you hook it up.
So please take it somewhere and get someone to clean out that port and hook it to vacuum. I gaurantee this will solve you problem. And please let me know when you get it done.