"Pulsations" at idle?!?!

[MaxSE]

Just noticed this the past couple of months, while waiting at a light with the shifter on "D" and foot on the brake the engine seems to tremble, everyone now and then. When i do catch the tach when it happens, the revs seem to bounce up within 100-150rpm of normal idle. It's very unpredictable, occurs at least a few times every weeks. I don't know if this could be a case of knocking, cause i don't know what knocking would feel like, and i really doubt it cause it's been getting nothing but premium fuel since day one.

Possible factors that i can think of:

1) Keys were reprogrammed by nissan back in august 2002 because the immobilizer system kicked in,according to the dealer someone tried to steal the car and therefore put something other than the original key in the ignition resulting in complete immobilization.

2) The "engine serv.soon" light came on in dec.2002, brought it to nissan, they said it was the oxygen sensor, so got that changed. The problem stopped for about 2 weeks...

3) I live in Montreal Canada, winter it's freaking cold here! Maybe it has something to do with the weather? cause this problem only started when the temperature seemed to drop. Way back in October 2002.


Hope someone can help!

Thanks!

[n1smo]

You'll definitely know if your car was knocking. Your engine will have a pinging sound when you are going uphill or during acceleration.

Your explaination was so broad that it is hard to pin down what is wrong with your car. There are many reasons for what you stated. One reason might be your car is not getting enough fuel... This can be a cogged fuel filter or injector. How many miles do you have? Being that it is a 99' I would say you have around 60,000. So if you or the dealer still have not changed it, it is time. Other reasons could be clogged/bad PCV valve, and bad spark plugs. And then ofcourse your MAF sensor could be bad or your ignition coil is bad. There are a lot that can be wrong with your car. So start with the easy stuff such as sparkplugs and fuel filter. PCV valve is also easy to clean/replace if you know where it is located. Invest some money in a service manual if you don't take your car to the dealer to be serviced. These cars are not mantainence free as Nissan marketing department would have you think. And no, those spark plugs do not last 60,000/ 100,000 miles. I switched mine out at 50,000 miles...