MAP Sensor

[Drover181]

Anyone know that if the map sensor is gone on a 96 grand am 2.4L will it start? mine poped the hose off a few times and would start but not enough power to move so now i replaced the hose yesterday so it wont pop off again and she wont start at all, when she was running she was running real rough like she was missing and this all started when the hose came off the map sensor. I checked the codes on it and it did come up map sensor. Oh and also do anyone know if these can be tested>?

[J-Ri]

If you can look at live data with whatever you checked the codes with, look at the MAP reading. Should be barometric pressure with KOEO.

Otherwise, you can check the resistance. I don't know off hand what it should be. If I remember, I'll check while at work tomorrow and post what i find.

[xeroinfinity]

Yeah the MAP controls engine timing and fuel delivery.
So yes if its bad it may not start or run properly.

Testing the MAP....
Backprobe with a high impedance voltmeter at MAP sensor terminals A and C.
With the key ON and engine off, the voltmeter reading should be approximately 5.0 volts.

If the voltage is not as specified, either the wiring to the MAP sensor or the PCM may be faulty. Correct any wiring or PCM faults before continuing test.

Backprobe with the high impedance voltmeter at MAP sensor terminals B and A.
Verify that the sensor voltage is approximately 0.5 volts with the engine not running (at sea level).

Record MAP sensor voltage with the key ON and engine off.

Start the vehicle, verify that the sensor voltage is greater than 1.5 volts (above the recorded reading) at idle.

Verify that the sensor voltage increases to approximately 4.5. volts (above the recorded reading) at Wide Open Throttle (WOT).

If the sensor voltage is not as specified, check the sensor and the sensor vacuum source for a leak or a restriction. If no leaks or restrictions are found, the sensor may be defective and should be replaced.

Hope that helps.

[Drover181]

Changed the Map Sensor and the thing will still not start it wont even offer to start, even tho the code was coming up for the map sensor.

Any ideas where i should start troubleshooting or maps of the vaccume hoses

[xeroinfinity]

Well the first question I'd ask is why did the hose pop off...

How are the spark plugs ?
You could have other ignition system components failing.

What exactly was the code(s) you got ??

Are you getting fuel ?

[Drover181]

Plugs were changed about 5000km ago probably less so i'm assuming they are good

ahh i don't know if i'm getting fuel but the fuel pump is cutting in. Anyway to check for fuel besides taking out the plugs to see if they were wet?

The 2 codes i am getting is
P0107
P0108

and i dont know why the hose poped off thats what seems strange, shouldnt there be vaccume on that? My thoughts was the hose was weak and just able to fall off the map sensor easisly but he wasn't that loose. He came off twice while the car was being driven.

Oh and i do have 5 Volt going to the sensor and the ground is good on it too

[Drover181]

Ok so some progress, i hauled all 4 plugs out and all of them were blackened right up and no spark on any of them not the smallest bit. Getting new plugs as we speak and gonna try that but what would cause all 4 plugs to do that?

[Drover181]

Put an old set of plugs in the car and she started but still has a miss to her like she did when the map sensor was acting up but now no code shows up, now could be the plugs, gonna get a new set tomorrow and try but still wondering why the plugs fouled

[J-Ri]

If the car is burning oil, that can cause the plugs to foul real fast. Do a compression test to see if the rings are leaking. On the first test, do it normally. On the second test, put a few drops of oil in the cylinder being tested. The oil will temporarily seal the rings, so if the pressure comes up on the second test, the rings are not sealing properly.

Also, if the black is carbon deposits from the engine running rich, the MAP sensor could be the cause, telling the computer the load is higher than it is, and delivering more fuel.

[Drover181]

Well the car has 330000km on it but i dont think its burning oil and if it is it's not much add probably half a quart between oil changes and shes leaking a small drop. the plugs themselfs were black like carbon built up on them not like an oily substance. Guy at a gm dealership told me it could be the fuel pump not delievering enough fuel, any imput on that?

[xeroinfinity]

The Map sensor reads intake pressure, low vacum/wide open throtle, high pressure/closed throtle.
It sends this voltage signal to the PCM, which controls the fuel delivery and Ignition timing.
I'd say you are on the right track. Have the Ignition module tested I bet that's your trouble.

Also the engine probly back fired poping off the hose on the Map.

Hope that helps

[Drover181]

How do you go abouts testing the Ignition module??? hes under the top pan with the coils right?

[J-Ri]

Originally Posted by Drover181

Guy at a gm dealership told me it could be the fuel pump not delievering enough fuel, any imput on that?

Was he wearing a clean shirt and sitting behind a desk/counter?

If it's running lean (not enough fuel), the plugs would be white-ish. Running rich causes them to be black.

[J-Ri]

Originally Posted by Drover181

How do you go abouts testing the Ignition module??? hes under the top pan with the coils right?

I would take it to a parts store that offers free testing. They'll almost always allow you to return the one you buy if they give you a bad diagnosis.

Yes, it's the box attached to the electrical connector that's visible at the edge of the cover on the rear of the engine (left side of car)

[Drover181]

Originally Posted by J-Ri

Was he wearing a clean shirt and sitting behind a desk/counter?

If it's running lean (not enough fuel), the plugs would be white-ish. Running rich causes them to be black.

lol nope this one was the mechanic haha

i'll get him tested tomorrow