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 Post subject: 1996 Dodge Neon Check Engine Light MAP Sensor?
PostPosted: Fri Oct 21, 2011 3:30 pm 
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I have a 1996 Dodge Neon that used to run really good and get excellent gas mileage. Then one day the check engine light came on and it has lost a lot of power, and runs kind of rough. When I sit a steady 40mph I can feel it kind of sputtering. It is now getting horrible gas mileage and you can smell gas in the exhaust. The engine code it gives me is "P0171 System Too Lean Bank 1". So far I have done a tuneup (spark plugs, wires, air filter, oil change, fuel filter, O2 Sensor). Doesn't run any better.

So I picked up a Chilton Neon Repair Manual, it says you can test the MAP sensor by checking the output voltage with the engine off but key in the on position, and again at a normal idle. It says it should should give 4.5 volts with the key on and engine off, When I tested it I got 15 volts! I didn't know that was even possible as the battery only gives out 12? Then when I start the car I dont think it was giving any voltage or around 1.5. (Did this the other day I forget now, I was testing all the different wires on the sensor. Only the 4th wire is the MAP output voltage. The IAT sensor is combined in it.)

Has anybody else experienced anything similar or know anything I don't or am missing? I figure its probably bad, but it is $85 at Autozone and money is tight, I would hate to replace it and still have the same issues with it.

Thank you for any advice, knowledge, etc. I really appreciate you even reading this.

-Jordan :bye:


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 Post subject: Re: 1996 Dodge Neon Check Engine Light MAP Sensor?
PostPosted: Sat Oct 22, 2011 9:52 am 
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Re test the map sensor before spending any cash.

Also check the fuel pressure first.

Better yet - Follow the diagnostic procedure for that code to the letter before wasting money changing good parts.

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 Post subject: Re: 1996 Dodge Neon Check Engine Light MAP Sensor?
PostPosted: Sat Oct 22, 2011 8:37 pm 
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Do you know where I can find a diagnostic procedure chart? The only one I could find had dead images. Thank you.


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 Post subject: Re: 1996 Dodge Neon Check Engine Light MAP Sensor?
PostPosted: Sun Oct 23, 2011 7:40 am 
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You can clean it for free, to see if that would help. Usually covered in oil being that the intake usually is too.

I wouldn't be so sure of the MAP sensor, anyways.

A lean code, coupled with a gas smell in the exhaust is typical of a vaccuum/exhaust leak. There could be too much air getting into the engine, and the PCM throws the code because it can't add enough fuel, or there is an exhaust leak before the O2 sensor and there is more air getting at it than is coming out of the engine - therefore making the computer think it's running too lean but infact it's running rich because it over-compensates.

Could also be: fuel pump, o2 sensor, bad catalytic converter.... list goes on.

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 Post subject: Re: 1996 Dodge Neon Check Engine Light MAP Sensor?
PostPosted: Thu Oct 27, 2011 8:11 pm 
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Ok so I cleaned the MAP sensor today, it was pretty oily. Sprayed some carb cleaner and gently blew it off with the compressor. Also found a broken vacuum line, doesnt seem like a very important one though. It just runs from the air intake hose to the valve cover. Anybody know what the vacuum line does? I searched it and I think it said its the air supply for the PCV? Dont think that would make my car throw that code and run so crappy. Dont see any exhaust leaks as far as I can tell. This sucks..


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 Post subject: Re: 1996 Dodge Neon Check Engine Light MAP Sensor?
PostPosted: Fri Oct 28, 2011 6:41 am 
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That's an important one. It's the PCV hose. With it broken you have a vaccuum leak.

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 Post subject: Re: 1996 Dodge Neon Check Engine Light MAP Sensor?
PostPosted: Fri Oct 28, 2011 8:42 am 
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Browno wrote:
That's an important one. It's the PCV hose. With it broken you have a vaccuum leak.

That sounds like the PCV hose to me too. And yes, that hose and the PCV valve are IMPORTANT.

The PCV (positive crankcase ventilation) system siphons the blowby vapors (combustion byproduct vapors, unburnt fuel vapors and ambient moisture) that collect in an engine's crankcase. The crankcase is sealed to contain the blowby vapors and keep them from polluting the atmosphere. However, the blowby vapors need to be removed from the system to prevent them from contaminating your oil (blowby vapors will turn into sludge in your oil). So, vapors from the crankcase via the PCV are moved into the intake manifold so they will be reburned during combustion.

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 Post subject: Re: 1996 Dodge Neon Check Engine Light MAP Sensor?
PostPosted: Sun Oct 30, 2011 7:36 pm 
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The vacuum hose does not run into the air manifold it runs from the plastic air hose before the air filter. Im going to replace it tomorrow and see if anything changes. Unlikely..


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