I put new throttle position sensor on now the car wont start i connected everything back on correctly so why wont it crank now ?

ANSWER : Hey there. Replacement of the throttle position sensor on your vehicle is pretty straight forward. There is no adjustment to be made – just remove and replace the sensor and you should be done. If the vehicle isn’t starting, you left something disconnected or there is a separate issue all together. If all of the work has been double checked and you still can’t get to the bottom of it then it is likely another problem that is occurring that is causing it to fail. You’ll want to see if the computer is still indicating a bad sensor even with the new one on. There are other sensors that could be causing the car to go into limp mode, such as a problem with the fuel system or another sensor on the vehicle. I recommend having another expert diagnose the starting problem so that this can be addressed properly.

ANSWER : Hi there. Check the spark plugs and see if they are worn or burned. If the plugs are good and they have a good spark, then the engine compression could be low causing a no start situation. If the spark plugs are not emitting a spark, then the crankshaft position sensor could have failed or disconnected. Check the crankshaft position sensor wiring harness and make sure that its plugged in. Check the sensor and make sure that its not broken or damaged. If you need further assistance with your engine not starting, then seek out a professional, such as one from Your Mechanic, to help you.

ANSWER : First, let’s make sure about some terminology before I proceed. I will assume the motor is actually turning over. If the car is trying to start, the motor has to be turning over or it is not trying to start. This is an important distinction when diagnosing the starting system. As a technician, I go to different parts of the system based on this description.

If the key is stuck in the start position, this is a ignition lock cylinder issue and the reason the starter continues to turn the motor over. If the starter is turning but the motor is not, then the starter is likely the problem. Either that or the teeth on the flex plate are all gone. This would require removing the transmission to repair.

If the car runs intermittently, this can be a big challenge. And it also means the starting system is working. It will need to be diagnosed when it is failing. A working car cannot be diagnosed because there is nothing wrong. Where you park your car should not have any affect. It certainly could be a wiring problem. Wiring problems hide really well and can happen anywhere in the miles of wires that are in your car. Isolating the system that is failing is really important here. At the moment I am unsure which system is failing. Starter system, ignition lock cylinder and or ignition switch electrical or something with the engine control system.

When the car is failing, you need to check for spark and fuel pressure. If neither is present, this is a clue. Usually the crank sensor will do this. Does your car have a tachometer? If so, does it move at all when cranking. This is a clue whether or not the cam and or crank sensor is working. Is there a Check Engine Light on with the key on? If there is a Check Engine Light, the code or codes can be used for specific diagnosis.

All of these concerns will send you down a diagnostic path. Be sure not to confuse yourself by misinterpreting multiple system failures. If the key does stick in the start position, this would be the first problem to solve. After that, does the motor actually turn when the starter turns? After that, the question of "Why won’t it start?" is first answered by finding what the motor is lacking. Fuel, spark etc… Good luck.

If you need assistance with these checks, contact a certified mechanic who has the tools and experience needed to properly diagnose this starting issue with your car.

ANSWER : Your MAP sensor is an important input for your computer. It helps determine the load on the engine to calculate the correct amount of fuel to inject. It sometimes takes a few seconds for the vehicle to realize that the sensor is not producing a good signal.

At that point, it will use other methods to determine the fuel rate, such as pre-programmed fuel maps, throttle position, etc. I would suggest replacing the MAP sensor and retesting. If you would like to have it checked first, a certified technician from YourMechanic will be able to scan your vehicle and test components to determine the root cause of your starting issue before making a repair.

ANSWER : The issue you are having is probably due to an intermittent fault in the starter motor itself or a deficiency in the starter electrical circuit, for example a large voltage drop due to a poor ground or a high resistance connection. These issues can be readily diagnosed and resolved on a mobile basis if you request a hard starting diagnostic. If you request that diagnostic, the responding certified mechanic will get this resolved for you promptly. Based on Toyota’s Factory Service Manual, the battery should not be disconnected if the vehicle engine is running. The battery acts as a large resistive voltage sink and consequently taking the battery out of the circuit, while the alternator is still running, can create a voltage spike on the car’s electrical system which is not good for voltage sensitive components such as the engine computer. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

ANSWER : Check the exhaust system for any leaks before the oxygen sensors. This can contribute to having more oxygen in the exhaust stream causing the sensors to register a false reading. If there is no leaks in the exhaust, then check the engine for any vacuum leaks. Look at all of the vacuum lines, the intake gaskets, and the brake booster. A vacuum leak will cause the engine idle to accelerate fast and also cause the engine to stall when the computer brings the idle down. If you need further assistance with your engine stalling, then seek out a professional, such as one from Your Mechanic, to help you.

ANSWER : With a car that cranks but won’t start, there are a few things that need to be checked. But before I explain them, there is a common thing that happens with Nissan’s. Every once in awhile they will flood the cylinders with fuel and wash the oil film off the cylinder walls and rings. This will reduce compression enough that the car will not start. Fortunately, there is an easy fix for this problem. It is what is known as clear flooding.

Hold the gas pedal all the way to the floor while cranking the motor. It won’t start immediately and when it does it will not run very well at first. Feather the throttle to keep it running until the motor clears out the excess fuel and the motor begins to run smoothly. If after cranking the motor with the gas pedal held to the floor for at least

ANSWER : Hi there – the behavior you describe could be caused by a faulty, or more likely disconnected, coolant temperature sensor sensor. If the coolant temperature sensor for engine management (not necessarily the sensor for temp gauge itself) is disconnected or there is a wiring fault, engine management treats this as VERY cold engine conditions, and provides a very rich mixture to the engine – yielding black smoke. Check to be sure the coolant temperature sensor is operative, and connected properly first. You are likely also getting a problem code, whether the Check Engine light is on or not. These codes will guide diagnosis as well. I recommend a not starting inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.