About 4 weeks ago, I noticed that on occasion when first starting my car in the morning, that just for the fist 50-70 seconds (around a minute), that the idle seemed to drop a little low and cause the car to vibrate just a tiny bit. Not very noticable at this point. Thought it may be due to change in ambient temperarture as it had been warm and gotten dramatically cooler around the time this began. Decided to keep an eye on it.

Stayed about the same for the next few weeks, although did begin to notice that on occasion when accelerating from a lengthy stop (long stop light or long wait at stop sign) that there would be somewhat of a lag period from when I pushed down on the accelerator and when the car really responded. Like a lowl, and then it would kick in and accelerate normally. Consulted some friends and itwas suggested that I try a fuel injection system cleaner. So did that, seemed to help with the lag issues as I did not notice it in the week following the addition.

Then starting mid last week, the idle issue seemed to become more dramatic. To the point where upon first starting the car in the morning, it wold idle to rpms so low that it came close to stalling out. Then I would hear the engine rev on its own as to compensate for the low idle and after that it would run smoothly and did not repeat the issue until the next morning–only mornings.

Today, it actually stalled out in the morning bc it idled too low. I restarted the engine and then it ran along smooth the three mile distance to work. Decided to take it into the shop, and after stting for about 2 hours it started up fine and did not idle out or stall.

Got to the shop, and explained the symptoms and when I came back to get the car, it was not fixed, as they said they had checked the fuel pressure and that was good, as well as the vacuum system which was good. They wanted me to bring it back in the morning so that they could work on it cold. As I left the shop, it was horrible. At least 30 times worse than when I dropped it off. So bad, that I could not even get it home. It was as if the fuel was just not circulating evenly.

The car is a Nissan 2001 Sentra. Never had any work done other than new radiator hose and thermostat. Some people have told me that spark plugs and wires can cause this issue and that it may just need a tune up. All belts appear fine. There is a check engine light on, that has been on for months. The code is generic and does not indicate much of anything (according to the shop mechanic).

Can anyone offer some help? I do not want them running up my bill, especially if all it needs is a tune up. I asked the guy what he thought it may be and he just said it could be a number of things-generic answer. Mentioned a mass flow sensor, but then said he did not think that was it….

Any help out there, would be greatly appreciated. I am in urgent need, as I need to speak with these people tomorrow.

Thanks in advance!
Thank you all for your quick feedback. I had always heard that you could take your car into an AutoZone and places like that and they could tell you what the code meant as well. And maybe I did not phrase it correctly, but it did give code, the mechanic just said that there could be several things that could be the culprit. (This is not my usual mechanic, as I moved and am due for a short business trip Thursday, and needed it handled). I know they said the code was definatley something to do with the fuel system, if that helps.
EDIT: I am going to add this in here, just for future reference in the event someone else has this question.

It turned out that the code was indicative of a fuel system error. Since there are several components to the fuel system, and some of my descriptions and previous work had ruled out some of it, they were able to figure it out today. It turned out to be the mass air flow sensor/controller as well as the cam sensor. Both components had gone bad. I just picked it up after work today an it is running well and the check engine light is off.

I will say tha the mark up on the mass air flow controller was steep (about 50%), the cam sensor was slightly cheaper than the average. So for anyone out there who can, I suggest getting the mass flow sensor from an auto store yourself, and eith putting it in yourself, or finding a place that will put in the part you bought for you.

Thanks. Because you were all very responsive I will let this one go to vote or will go w/ thumbs up