Nissan Repair: crankshaft & knock sensor replacement, crankshaft sensor, mercury villager

Question
QUESTION: I have a 1999 Mercury Villager with the 6V 3.3L Quest engine. CEL is on with codes for crankshaft sensor & camshaft sensor according to my husband (sorry don't have the codes handy). Engine runs but starts shuddering/hesitating as engine warms up & engine sometimes dies but will restart after sitting for a while. Took it to a mechanic today who quoted replacing the crankshaft sensor & knock sensor to the tune of $800. We can replace the crankshaft sensor ourselves, is it really necessary to replace the knock sensor or could it wait a couple months (3 months max)until we have the cash to do major maintenance as planned? Also what does replacing the camshaft sensor entail & why would the mechanic not quote us for that if the CEL was coding for the camshaft sensor?

ANSWER: Hi Mell -

First of all, it would be very helpful if I could get the exact codes, so I know what we are chasing. It would be better if you took it somewhere else, as it seems the quotes are very high. I think Autozone will download the codes for free. I just want to ensure we are targeting the right sensors.

The crankshaft sensor is relatively simple to replace, as is the knock sensor, however you may need to remove the intake manifold for that one. The camshaft sensor will take some time, if I remember correctly for the 3.3 engine. Maybe that mechanic did not want, or does not know how to replace that sensor, so he kept it out (I am just guessing).

So, I would clear the codes, and see if the CEL returns. If and when it does, then we can be sure that there are actual issues with the sensors.

I also would just replace the ignition module in the distributor. This would cause the engine not to start when it is hot, but will start later when the engine temp goes down.

Hope this helps -
aloha
calvin

---------- FOLLOW-UP ----------

QUESTION: the CEL codes were P0325 & P0340, the CEL has not reoccurred yet since resetting but we're not driving more than a couple blocks to the store & back at any given time. Current symptoms are the vehicle drives fine from a cold start but as engine reaches normal operating temp it will die while idling & small occasional hesitation/shudders while driving if continuing to drive, the longer it is driven the stronger & more frequent the hesitation/shuddering sensation becomes.

Answer
Hi Mell -

Thank you for getting the codes.
Sometimes there are many codes for the same device, some define high voltage, low voltage, circuit malfunctions, left side of the car or right side, etc, so the exact code will narrow down the search.

With that said, here are the definitions for the codes:

P0325 - Knock sensor bank 1 circuit malfunction (bank 1 is passenger side of the car)
P0340 - Crankshaft position sensor malfunction

Because the codes did not return yet, they are called soft codes, which is either intermittent or happen under certain conditions. In addition, "circuit malfunction" tells me that most likely it is not the sensor that needs repair. This is why I tell people to monitor first before jumping into an expensive repair that may not be the cause.

I would go ahead and replace that module in the distributor first and see what kind of result you have with that. Also, when was the last time the car was tuned up?

Hope this helps -
aloha
calvin