Question about 1991 Chevrolet S-10
My truck has been spiting a sputtering, I have changes the tps sensor, map sensor, cap, roto, wires, plugs, rebuilt carborator, and replaced vaccume lines, what could be causing my truck to not take off and die out and backfire all the time I have to constantly pump the gas peddle to keep it running.
Hello,when you changed the cap and rotor did you have them check the timming,the timing chain may have jumped a clog,fuel pump may be getting weak,check you air filter make sure you pull it out in case mice filled up the space undernieth the element,check or change fuel filter,,may be a bad batch of gas may have some water in it,,good luck..
Posted on Feb 09, 2013
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Posted on Jan 02, 2017
Spray the intake with carb cleaner to find the vacuum leak. Check where the EGR mounts and the throttle body gasket sense you had both off.
Posted on May 10, 2009
It sounds very likely that it is going lean. Could be a bad Mass airflow sensor or a fuel pump, maybe plugged injectors. The first thing to do if you can get your hands on one, is to put a scan tool on it that reads live data and go up a long steady hill while you are watching the O2 sensor voltage. It should toggle back and forth across .5V, if it remains below .5V while you drive, then you know it's not getting enough fuel. If so, check the fuel pressure to spec. If it is good, then the pump is fine and you're chasing the other two.
Posted on Mar 08, 2009
TPS probably not cause surging idle. Could be IAC motor, could be MAF sensor. If you dont have a check engine light I would be thinking IAC motor.
Posted on Jan 21, 2011
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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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