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post #1 of (permalink) Old 09-04-2002, 08:12 PM Thread Starter
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OT - My Daughters Car Troubles :(

Hi All
I know this isnt Jeep related but it`s within the Jeep family . My daughter who`s going to school has a 89 Pontiac Sunbird w/ 2.0L . Its quit running and the code I`m picking off the computer says the MAP sensor is indicating a LOW signal . Ok anyone have any clue as to what that actually means [img]images/icons/smile.gif[/img] ?
Timing belt is new etc... Could the Oxygen sensor going bad cause that to read low . I`ll be honest , I can do anything on the Jeep engine blindfolded but when it comes to the computer controlled cars , yuk . Just thought someone might have an idea or something . Thanks as always !!


Jeff
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post #2 of (permalink) Old 09-04-2002, 08:24 PM
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Re: OT - My Daughters Car Troubles :(

More than likely the MAP sensor is bad. Early GM MAP sensors were prone to failure. They are cheap and easy to fix. Make sure you dont have a vacuum leak first, then try replacing it. Hope this helps...
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post #3 of (permalink) Old 09-04-2002, 08:32 PM
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Re: OT - My Daughters Car Troubles :(

MAP - Manifold Absolute Pressure if I remember correctly. I'm not that familiar, I've got the MAF.

Low reading could be grounded wire. If you don't see anything, change it out. I think about $30. Search the web for GM error codes or GM trouble codes and you should find more information.
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post #4 of (permalink) Old 09-04-2002, 08:35 PM Thread Starter
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Re: OT - My Daughters Car Troubles :(

Ya everything helps . I was just thinking if it was showing low due to some other component failure . It also showed a code 44 which is Lean Exhaust . Thanks


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post #5 of (permalink) Old 09-04-2002, 09:24 PM
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Re: OT - My Daughters Car Troubles :(

The two codes could be correlated. The MAF/MAP sends information to the ECM about the engine load... how hard it's working. The ECM then leans or enriches the mixture to take into account the load. So, depending on what happened to the sensor, the engine could have been being trimmed too far back on gas and power loss and overheating could be the result until the sensor finally fails and is outside the ECM parameters and an error code is thrown showing two codes, not just a MAF/MAP sensor failure.
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post #6 of (permalink) Old 09-04-2002, 11:59 PM
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Re: OT - My Daughters Car Troubles :(

Typically if it was just a vacuum leak ..it would be accompanied by a high idle. If you unhook the PCV hose the idle will go high and you'll lose all your air doors inside. Swap out the MAP sensor.

Funny though ...I was unaware that a faulty MAP sensor totally disabled the vehicle.
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post #7 of (permalink) Old 09-05-2002, 08:54 AM
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Re: OT - My Daughters Car Troubles :(

I'm guessing that a bad MAP sensor will fool the computer into thinking there is no vacuum. Thus it thinks its WOT and floods the engine.
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post #8 of (permalink) Old 09-05-2002, 06:32 PM Thread Starter
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Re: OT - My Daughters Car Troubles :(

Leve , would a faulty MAP sensor make the vehicle not run at all ? What about a bad Oxygen sensor ? I`m thinking that the O sensor would just make the car run to lean/rich . I`m trying to do the best home work I can before going out and buying my armful of new sensors [img]images/icons/laugh.gif[/img] . Thanks for the all the input guys ! If she ( my daughter) wasnt on the tight college budget I`d take her out and go (semi-new) car shopping . If you`ve had kids in college ( I think you have had , Larry ) you know what kind of extra money they have ( and thats including DAD`S help , hehe) .



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post #9 of (permalink) Old 09-05-2002, 07:39 PM
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Re: OT - My Daughters Car Troubles :(

Jeff, don't discount there could be more than one problem contributing the overall "it ain't running" result. But try first to work on one at a time. I've seen MAP sensors foul up the EFI to the point the ECM is brain dead. It's a place to start. If the engine uses a two step process for setting the EFI, open and closed loop then in open loop the MAP and O2 sensor should be out of the loop. This condition is only when the engine's cold, like when you're trying to start it.

Does the engine cough or sputter? Is there spark? Are the plugs wet, fuel fouled?

More often a bad MAP can cause hard starting, stalling, and missing. In later model EFI even uses the MAP to help decide when to up and down shift the transmission as it is a fairly reliable indicator of manifold vacuum. This may be being used in Open Loop if the EFI's new enough.

As to the O2 sensor... heck you unhook it and the car should still start and run but like you said.. run rich. It's not a bad idea to take the O2 sensor out every now and then and wire brush the housing to free the vents. They can become clogged and then they're not able to sense the mixture and it drives the ECM nuts by sending it a false reading.

At this point I'm not thinking the 02 senosr is involved.

Drop back to basics... we need more input, again:

Do you have:
Spark
Fuel
Air
Timing

What's missing?

And you're right:

College + Kids = NO money. I've had kids in college the last 10 years and now you all know why my Jeep's the ugliest thing on 4 wheels... I think it still has four wheels... it's been a long time....[img]images/icons/frown.gif[/img]
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post #10 of (permalink) Old 09-05-2002, 08:00 PM Thread Starter
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Re: OT - My Daughters Car Troubles :(

Larry

She is on her second computer in this car . Had a re-manufactured one put in last Christmas . I`m going to double/triple check the spark , fuel etc.. and report back tomorrow . I guess the codes I`m pulling from the comp. right now are saying what condition it was in last time it was actually running , correct ? OPEN Oxygen Sensor Circuit and LOW signal on the MAP sensor . That doesnt really mean that those components are bad , right ? I`ll have more info. tomorrow . Thanks again !

If I havent mentioned it , its like a good old motor with the distributor way to far advanced , you know like it really wants to catch , but just doesnt .


Jeff

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