Chrysler Repair/intermittent shutdown problem: 3.3L '99
QUESTION: Its me again with the same problem and a new indication of where the problem may lie.
I drove about 600 miles two days ago. During that time, it happened several times momentarily and all times my foot was on accelerator and therefore I can rule out idle control valve and egr valve for sure. Now, every time it happened, I noticed that the rpm does not reduce at all. However, the speed needle takes a big dip like from 120 km/h to 60km/h in a split second. Now, I know that the speed did not actually reduce in half in that split second (the car just took a quick jerk). Based on this observation, I believe that something might be wrong with the speed sensor(s). I was checking reviews on advance auto parts and noticed that one user has left a comment that replacing a speed sensor fixed a misfire! What do you say? Is it possible? How many speed sensors are there on this vehicle?
Thanks for your help.
ANSWER: Hi Shafique,
There is an input torque converter speed sensor near the torque converter bell housing and then there is an output speed sensor at the far end of the transmission. They look identically to one another and are mounted on the side of the transmission facing the front of the vehicle. It is possible that the output sensor is getting flakey, or that the wiring from it to the transmission control module is flakey. The engine and the transmission on-going operations are impacted by both sensors so it is conceivable that a momentary loss to the output speed sensor would provoke not only a drop in the speedometer but also the engine to 'miss' because of a false reading of the output speed. So check the harness for the rear sensor and if that seems alright then try replacing the sensor.
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QUESTION: Two more questions:
1) Are these input and output sensors identical? (or just identical looks as I see that advance autoparts is selling these separately.
2) As I understand from your explanation that the symptoms that my van is having can only be caused by OUTPUT speed sensor and that I do not need to worry about input speed sensor. Am I right?
ANSWER: I would believe that they are not identical because they are sold for a specific location/purpose.
I would believe that the engine function would not be impacted by a defective input speed sensor. I am not certain whether the dip in the speedometer reading will explain the momentary engine shutdown, but your observation that the speedo reading when it happens is much more significant than the actual slowdown of the vehicle suggests it may be playing a role in initiating the momentary shutdown. However, because the speedo reading is based upon an electrical signal that goes from the sensor to the TCM and then to the PCM via the data bus, it may not be the cause of the shutdown but rather just another manifestation of it, what ever is the real cause. So don't be surprised if replacing the sensor does not solve the problem.
Let me know either way, please.
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QUESTION: I want to know if there are any precautions while replacing the Output speed sensor. As I understand:
1) This is the sensor located outwards towards the driver's side.
2) Just need to unscrew the old and screw in the new one.
Am I right?
Yes, the sensor is located just to the right of the vertical shifting rod. When removing it be sure that the weather seal is transferred from the old one to the new one. The torque spec is about the same as for a spark plug, 20 foot-pounds.
Thanks for the prior answer rating/nomination. Feel free to do the same for this one.