My Tahoe is not wanting to start
My car has 145000 miles.
My car has an automatic transmission.
The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer which will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage.
When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed. This is all controlled by the idle air control valve. When the engine RPM drops below the normal range of 750-800 RPM (for most cars), this may indicate a dirty or faulty idle air control valve.
In cases where this valve is dirty or failing, your vehicle may stall instead of slowing to an idle after the release of the throttle. I would recommend having an expert from YourMechanic come to your location to diagnose the hard start and replace the valve if necessary.
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If the cranking of the engine is sluggish, like your vehicle is harder to start on cold mornings, it starts inconsistently, or there`s no sound and interior lights when you try to start, suspect a failing battery, a loose or corroded connection or electrical draw.
An oxygen sensor monitors and analyzes the amount of oxygen in a vehicle`s exhaust system after combustion. A dirty, damaged or malfunctioning O2 sensor (or sensors) affects the air/fuel mixture, causing the engine to idle rough.
Perhaps your battery`s dead, or your alternator, which charges the battery, isn`t working correctly. If the source of the clicking is electrical, the starter (a small motor energized by the battery that gets the engine running) doesn`t have enough juice to stay powered.
One common culprit for this problem is the crankshaft position sensor, which measures the position and speed of the crankshaft. The computer uses the information from this sensor to know when to fire the spark plugs. If the sensor isn`t working, the spark plugs won`t fire, keeping the engine from starting.
Perhaps the single most common cause of rough idle comes in the form of a misfiring engine. As you may know, any automotive engine contains multiple cylinders. Each of these cylinders contributes to powering your car by combusting a mixture of gasoline and air.
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The GM 3.8l motor has been installed in Buicks, Pontiacs and Chevrolets for decades. Particularly during the 90’s and early 00’s, these motors have used an ignition module with three coils mounted to it. This module is prone to just this type of failure. When it gets too hot, it quits working. When it cools off, it starts again. It can also display intermittent no start conditions. This is a pattern failure on this particular motor. Before I would ever replace the module, I would check for spark and injector pulse. If it just lacks spark, I would check for a crank sensor signal and replace the ignition module.
Before we get too far ahead of ourselves, do a few tests first:
Check fuel pressure. If there is none, check the fuse and the relay.
Check for injector pulse with a noid light. If this is missing, I would suspect a crank sensor. It could be a bad Power Control Module (PCM). (PCM’s are very rare to fail. I have never changed a PCM on one of these cars.)
Check for spark with a spark tester. If it is lacking spark but has injector pulse, suspect the ignition module.
If all these are present, I would take a compression test of all the cylinders. If camshaft timing is off, several of the cylinders will have significantly lower compression. Also, camshaft timing won’t start sometimes then not others; it will either start and run bad or it won’t start at all. It may sound like it is trying to start, but it won’t start.
If all of this sounds to daunting, I recommend booking a car is not starting inspection with YourMechanic
It can also be a weak fuel pump or an air flow meter issue. If the engine runs fine once it is started, then I would check the computer for codes first. If none are present, then I would run the engine and see what the sensor readings are to see if anything comes up faulty.
If those are also fine, then I check the fuel pressure to see if the pump is getting weak or to see if the pressure bleeds off while the vehicle sits. If you are thinking of having this starting issue inspected, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair this problem.
The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal. When this happens, the job of the idle air control valve is to bring this deceleration down to a slow and smooth idle rather than suddenly cutting off the fuel supply causing the motor to die. When the idle air control valve is not working properly, this cause a disruption in this process resulting in the engine not being able to idle properly. I would recommend having a professional come to your location to diagnose and inspect your vehicle.