Question about 1991 Chevrolet Lumina
If car has a carburetor instead of fuel injection, lokk down into the throat of the carburetor and see if you can see small amount of fuel dripping, if so the needle and seat inside the caruretor are probably dirty and stuck, causing you the problem. Could also have a vacuum hose off or cracked/broken.
Posted on Apr 30, 2010
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Posted on Jan 02, 2017
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Jul 08, 2014 | 2001 Pontiac Sunfire
Fig. Fig. 1: ALDL connector-1994 models
Listings of the trouble for the various engine control system covered in this guide are located in this section. Remember that a code only points to the faulty circuit NOT necessarily to a faulty component. Loose, damaged or corroded connections may contribute to a fault code on a circuit when the sensor or component is operating properly. Be sure that the components are faulty before replacing them, especially the expensive ones. The Assembly Line Diagnostic Link (ALDL) connector or Data Link Connector (DLC) may be located under the dash and sometimes covered with a plastic cover labeled DIAGNOSTIC CONNECTOR.
Fig. Fig. 1: Typical Manifold Absolute Pressure (MAP) sensor
wiring diagram (wire color, terminal identification/location may vary on
Fig. Fig. 2: Using jumper wires and a high impedance voltmeter
test between MAP sensor terminals A and C with the key ON and engine
off. The voltage should be approximately 5 volts
Fig. Fig. 3: Next test between MAP sensor terminals A and B with
the key ON and engine off. The voltage should be approximately 0.5 volts
Throttle position sensor test
TESTINGSee Figures 1, 2 and 3
Fig. Fig. 1: Common Throttle Position Sensor (TPS) wiring diagram
(wire color, terminal identification/location may vary on certain
Fig. Fig. 2: Using jumper wires and high impedance voltmeter, test
between the sensor ground and reference terminals, the voltage should
be approximately 5 volts
Fig. Fig. 3: Next test between the sensor signal and ground
terminals, verify that the TPS voltage increases or decreases smoothly
as the throttle is opened or closed
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Fig. Fig. 3: Location of the MAP sensor-TBI system shown
Fig. Fig. 4: Probe the terminals of the MAP sensor to check for proper reference voltage
Fig. Fig. 5: Manifold Absolute Pressure (MAP) sensor wiring diagram
TPS TESTINGSee Figures 2, 3 and 4
Fig. Fig. 2: Using a DVOM, backprobe terminals A and B of the TPS sensor to check for proper reference voltage
Fig. Fig. 3: Using the DVOM, backprobe terminals C and B of the
TPS sensor, open and close the throttle and make sure the voltage
Fig. Fig. 4: Throttle Position Sensor (TPS) wiring diagram
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Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction
The MAP (Manifold Absolute Pressure) sensor is part of the fuel management system. It reacts to changes in engine manifold pressure. The PCM (Powertrain Control Module) monitors the MAP sensor continually to properly run the engine. Changes in engine load require changes in the amount of fuel injected, and timing of the ignition system, etc. An engine under load has more manifold pressure(or less vacuum) than an engine that is coasting. As the load changes, the MAP sensor voltage signal to the PCM changes accordingly. To check the MAP sensor operation, though, the PCM watches other sensors to verify that the MAP sensor is working properly.
For example, the PCM compares the TPS (Throttle Position Sensor) signal to the MAP signal to verify the MAP signal isn't "sticking". If the PCM doesn't see a MAP sensor change immediately follow a change in the throttle pedal sensor, it knows there is a problem with the MAP sensor and sets P0105. Or, if the PCM notices that the TPS indicates the engine is under load, but the MAP signal indicates that the engine is "coasting" it, again, knows there is a problem with the MAP sensor or TPS and sets P0105.
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Symptoms of a P0105 check engine light code may include:
A P0105 DTC could be caused by:
Using a scanner or code reader, turn the ignition on and engine OFF; what does the MAP sensor voltage read? It should be about 4 Volts for sea level. If you are at a higher altitude, it should decrease about half a volt or so for each 1,000 ft. of altitude (this will vary from model to model) Or if you have a separate MAF (Mass air flow) sensor on your vehicle, they are usually equipped with a Barometric pressure reading. If so, the Baro reading should match the MAP reading (they both measure ambient air pressure). If they're roughly equal, then, check for Freeze Frame data of the MAP sensor (if available).
NOTE: Freeze Frame data is the PCM recording a fault when it happens. It captures the readings of the various PIDS (parameter identifiers)available to troubleshoot what happened. It's like a recording of the problem as it happened. At idle a typical MAP sensor Voltage reading should be about a volt, and at WOT (wide open throttle) it should approach 4.5 to 5 Volts. As for the TPS, at idle, the voltage reading is about 1 Volt or less. As the throttle is opened the reading will increase to 4.5 Volts at WOT. Do the two readings make sense? For example, if the TPS reading on Freeze Frame data shows 2.5 Volts (indicating partial throttle) does the MAP sensor indicate a reading that isn't at either extreme? Using the Freeze Frame data (if available) compare the MAP reading to the TPS when the problem occurred. This can help you identify what happened
If you have no access to Freeze Frame data then check if the MAP sensor voltage changes when you apply vacuum to it. You can do this by mouth or a vacuum pump. The voltage should increase as you apply vacuum. If the reading doesn't change as you apply vacuum, make sure there are no obstructions in the hose to the sensor. If the hose is clear, the MAP sensor is usually bad, but it doesn't rule out the following from causing the problem: Does the MAP sensor appear to be stuck at less than .5 Volts? Then:
NOTE: This code shouldn't set if the MAP is stuck at extremely low voltage, however, I'm adding it in because there's no way to know for certain for which vehicles a low voltage condition may set a P0105.
Does the MAP sensor appear to be stuck at full 4.5 voltage? Then:
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