Question
sensors on the air man
QUESTION: Hi,we have a problem with our Hyundai excel x3 car that stops while driving. when the car engines stops there is a knocking/vibration coming from the middle sensor on the air manifold. the sensor seems warmer than the other sensors and the engine will not start until this unit cools down. we have a spare unit and swap it over and the engine is fine again. The car may run fine for a week or two then it stops again...again we swap the unit over with the old one and the engine starts again. The part number in a kefico 9 540 930 001. sorry for the vague use of technical terms, if needed I could send you a picture.
many thanks
Mark brooks
ANSWER: The component you're describing is the idle actuator. If the ignition is on and the engine is not running, it's normal for the actuator to vibrate. The reason this component is warmer than the others is that it actually has a motor inside, whereas the other two (the MAP sensor on the bottom of the picture and the throttle position sensor on the top) are simply electronic sensors. My initial speculation is that the idle actuator isn't the cause of the stalling; it's more likely that a faulty crank sensor would cause this.
If you're able, interrogate the engine control module (ECM) for trouble codes.
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QUESTION: Many thanks for your reply.
could you tell me were I can find the crank sensor? I will change this too. Also it seems weird that when the engine wont start and we change the idle actuator, the engine fires up fine!
Also would the idle actuator have a relay that might be faulty if so where can I find this.
One more question.....sorry to be a pain. Interrogating the ECM, will the trouble codes appear even when there is'nt a fault, just wondering if they are stored for intermittant faults.
Thanks for your time
Mark Brooks
AnswerThe crank sensor mounts directly in the engine block. It's in the front on the transmission end of the engine beside the oil pressure switch.
I agree it seems odd that the problem goes away when the idle actuator is changed, but if the idle actuator were actually the issue, I wouldn't expect it to be the same with both actuators. It's more likely that changing the actuator allows enough time for the faulty component to cool.
There is no relay for the idle actuator. It is directly controlled by the ECM.
If there is no fault, the ECM should not store a code. In your case, there's obviously some sort of fault, since the engine cranks but does not start. Whether this fault is recognized by the ECM is hard to say (unless the check engine lamp is turned on) without checking for diagnostic trouble codes. The ECM will store a code the first time it sees a fault, but will not turn on the check engine lamp until the problem occurs at least once on each of two consecutive tests.
