Undiagnoseable problem?

I’ve had an ongoing issue for a few months. While my car is idling, it will start to shake as if it’s about to run out of gas or stall. The problem only occurs sporadically - once or twice a week - but lately, it has been happening right after I start the car whereas previously it occurred while stopped at lights, etc., also. I also smell gas fumes while the car is shaking. After driving for a minute or two, the shaking will stop. At times, it’s accompanied by the check-engine light flashing on and off, but the light does not stay on and no repair codes are saved in the computer. So when I take it to the repair shop, they basically tell me they can’t diagnose the problem because no codes were saved. I have had the throttle body cleaned, which helped for a couple of weeks. I’m at a loss - don’t know what the problem is and the two repair shops so far have basically been too lazy to do any investigation further than checking the codes, despite my requests. Any suggestions?

Model year, mileage…

It’s a 2003 with about 93,000 miles on it.

It’s hard to say much about what to do next without knowing the model year of the car and which engine it has.
The flashing check engine light means that a misfire is occurring, and that you are damaging your expensive catalytic converter(s).
Even after the light goes off, the check engine codes are retained and readable for at least a few driving cycles. The next time the light comes on, go directly to an auto parts store to see if they can retrieve the code(s) for you, even if the light is off. If not, then you will have to go somewhere with a Nissan specific scan tool. You don’t want to put this off, as this problem will cause more and more damage.

When is the last time you got new spark plugs and wires, fuel filter and air filter? Has anyone checked the fuel pressure?

Alison, As Others Have Suggested There Are Many Possibilities Here. Nothing Points At A Specific Cause For The Problem And Unfortunately, Intermittent Problems Present A Bigger Challenge.

[list]Do you know if you have the QR25DE engine ? Maybe there’s a sticker under the hood that indicates which engine you have.[/list]

[list]When you give it some gas when it’s idling roughly, does it then run well ?[/list]

There is a Nissan TSB (Tehnical Service Bulletin) that addresses the above 2 symptoms and guides Nissan Technicians through an ECM (engine control module) reprogramming procedure.

Alison, please be advised that this is one of many guesses and I’m not implying that this bulletin and procedure will fix your car. Obviously if mechanics can’t fix it with the car in front of them, then to diagnose or fix it online is impossible. It’s just an example of one of many possibilities.

Has the car’s battery been run down (discharged) or did you have to replace it recently because it died ?

As Cigroller has suggested engine basics and basic maintenance cannot be overlooked. Is the car up to date on maintenance as outlined in the Owner’s Manual ?

As Tardis has suggested, a Nissan dealer may be best equipped to handle a problem of this nature.


Alison, Three More Questions . . .

[list]Did you find out if you have the QR25DE (apparently a 2.5L) engine ? [/list]
[list]Are you the car’s original owner ? [/list]
[list]Do you know if the car’s ever been into a Nissan dealer for a recall or voluntary recall ? [/list]

Calling a dealer, with your VIN (vehicle identification number) handy, will let them check to see if there are any “open” recalls on this vehicle.

I see that there was a voluntary recall for certain VIN 2003 - 2004 Altimas with the QR25DE (2.5L) engines to have their Crank Angle Sensor reprogrammed.

Although the recall is to keep cars from just shutting off while driving, I thought this reprogramming could get you in the door of the dealer and hooked up to their computer and possibly go through the idle relearning procedure.


Bumped Up. Waiting For Response.

I have taken it to the Nissan dealer within one driving cycle, and they have told me there is no code saved.

I hope you brought a lunch because you probably will be waiting a while, what am I talking about? It seems when we give our readers even just a small job like this the result is no response back. It seems if we cannot provide an absolute answer without requesting more info,we are not so useful.

In fairness, the OP did respond today (4th post down). Still no info on which engine though.

Actually, I responded twice, but one of the posts did not appear. Here’s the information again: There are no open recalls on the car, so I don’t think it’s a QR25DE (2.5L) engine as the dealer told me there were no recalls associated with my VIN number. I have taken it to the Nissan dealer to look at the problem twice now. Basic maintenance is complete and up to date per the manual but I have not recently changed the spark plugs. The battery was most recently discharged in November when a tune up was done. The battery was replaced when I bought the car in 2008. When I give it gas after it is idling poorly, it does not help - I have to drive it for about a minute before it improves. I’m thinking it might be an engine intake manifold leak.

If your 2003 Nissan is a 4 cylinder Altima, then you have the QR25DE engine.
If you have the 6 cylinder, 3.5 liter engine, then the engine code is VQ35DE.

Are there any TSB’s that apply to your car and situation? TSB’s are different than recalls.