Map Sensor 305 Carburetor?
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Map Sensor 305 Carburetor?
I have a 1985 Trans Am 305 with a carburetor. I am getting a check engine light code 34 (MAP sensor circuit error (signal low indicating high vacuum)...
Does the carb motor have a Map Sensor?
The car runs no problems...
Any advise would be appreciated...
Does the carb motor have a Map Sensor?
The car runs no problems...
Any advise would be appreciated...
Joined: Feb 2017
Posts: 4,174
Likes: 569
From: Meriden, CT 06451
Car: 84 TA orig. 305 LG4 "H" E4ME
Engine: 334 SBC - stroked 305 M4ME Q-Jet
Transmission: upgraded 700R4 3200 stall
Axle/Gears: 10bolt 4.10 Posi w Lakewood TA Bars
Re: Map Sensor 305 Carburetor?
Joined: May 2004
Posts: 5,338
Likes: 73
From: Lexington, SC
Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
Re: Map Sensor 305 Carburetor?
the carb does not have a MAP sensor. it does have a vacuum sensor and associated barometer sensor that provides the ecm the info it would otherwise receive from a MAP sensor.
the vac sensor is located near the brake booster and should have a thin, hard plastic vacuum line connected to it, run through the ECM harness and attached to the rear of the carb. the vac sensor seldom fails but the vacuum line can become disconnected or broken. the code you get refers to the vac sensor on the carb cars.
the baro sensor looks identical, is attached to the cowl near the blower motor but does NOT have a vacuum line connected to it.
the vac sensor is located near the brake booster and should have a thin, hard plastic vacuum line connected to it, run through the ECM harness and attached to the rear of the carb. the vac sensor seldom fails but the vacuum line can become disconnected or broken. the code you get refers to the vac sensor on the carb cars.
the baro sensor looks identical, is attached to the cowl near the blower motor but does NOT have a vacuum line connected to it.
Joined: Sep 2005
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Car: Yes
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Re: Map Sensor 305 Carburetor?
Vacuum is the same thing as MAP, except that MAP (Manifold Absolute Pressure) is independent of atmospheric pressure. That is, it is the absolute pressure, referenced to 0 pressure (hard vacuum), whereas vacuum is referenced to atmospheric.
That's the reason why the later carb systems have both a MAP and a baro sensor... "vacuum" is the difference between the 2. With a MAP sensor only, such as the early cars had, the whole setup is very sensitive to atmospheric pressure; for example at high altitude.
So, that sensor with the vac line is in fact a MAP sensor.
Other than that, good advice.
That's the reason why the later carb systems have both a MAP and a baro sensor... "vacuum" is the difference between the 2. With a MAP sensor only, such as the early cars had, the whole setup is very sensitive to atmospheric pressure; for example at high altitude.
So, that sensor with the vac line is in fact a MAP sensor.
Other than that, good advice.
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Joined: Jun 2012
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From: Concord N.H.
Car: 1985 T/A
Re: Map Sensor 305 Carburetor?
The things you learn when you try to just read every new post at night.
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