I just replaced my crank and cam sensor and car still dont start

ANSWER : You should check to see if your vehicle has jumped timing. Have a mechanic verify that the camshaft timing did not jump after scanning and looking at the crankshaft sensor data to verify it is giving a signal. If it is giving a signal, then the cam and crank signals are way off and causing the wrong ignition timing. If you need to have a local expert come check this problem for you, a certified technician from YourMechanic can come to your car’s location to diagnose the hard starting issue and pinpoint the correct fix.

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 : Prior to performing diagnostics be sure you have a fully charged battery that passes a load test. Then, confirm that the engine immobilizer system (security system) is not activated thus preventing the car from starting. To temporarily override the immobilizer system, see these instructions.

Be sure there is adequate fuel in the fuel tank and that the fuel is not old. Check for adequate fuel pressure, injector operation, and a spark at the spark plugs. Basically, if the starter motor is turning the engine over rapidly, at sufficient RPM, but the engine does not catch and run, that means that there is an ignition, fuel, air induction, or mechanical fault in the engine that will have to be repaired. Strictly speaking, you should first check engine compression in the cylinders because if there is no, or inadequate, compression the engine won’t run under any circumstances. If compression is found to be within factory specifications, and there is fresh fuel being delivered by the injectors (not just "to" the injectors) and the ignition system is working, that means that the air fuel ratio of the mixture delivered to the cylinders is so far off that the mixture just won’t ignite. Such could be due to a big vacuum leak, an air induction fault like a stuck idle air control valve or, considering fuel, could be due to a failed temperature sensor that must be working properly to signal the PCM to enrich the mixture on cold start. Other common faults are defective spark plugs or a defective coil. Regardless of the underlying cause, if you request a no start diagnostic the responding certified mechanic will get the problem diagnosed and repaired for you promptly. Please let us know if you have further concerns or questions as we are always here to help you.

ANSWER : Hi there:

That is a very off symptom you’re describing. Without being there to phyisicaly inspect your Nissan, the only thing I’d guess that might be causing this is if the cam sensor you installed was the incorrect one, or perhaps the electrical harness created an electrical fault; causing the ignition relay to not send a signal to the starter relay. You might want to have a professional mobile mechanic complete a car is hard to start inspection; so they can determine why you’re having this issue.

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 : Hello there, thanks for writing in. I’d be happy to help.

If you replaced the sensor twice and the issue persists, then I would look at the connector and ECM as possible sources of the issue. I would carefully inspect the connector to the cam sensor for any signs of oil leakage, damage, or wear, both on the wires and on the metal contacts. If the wiring looks okay I would move on to testing the wiring to make sure that the correct signal is being generated, if it is not then it may be possible that there is an issue with the ECM or wiring. It may also be possible that the aftermarket sensors are the source of the issue, even if they are new. In many cases aftermarket components are not as high of quality as OEM components, and for that reason can cause issues.

If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make any repairs as needed.

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 : Hello. You will need to have the computer scanned and system checked for codes indicating the problem. You may have a bad crankshaft sensor or computer problems with the anti-theft system. If you would like to have this corrected, consider YourMechanic, as a certified professional can come to your home or office to pinpoint the cause of the starting issue and assist with repair.