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Nissan Maxima 2003

About 30 percent of the time you turn over the ignition and instead of the RPMs jumping to about 1500, they only go to about 900-1000 and then the car will die. It seems to help to depress the brake or gun the engine (you can bring it back from the brink most of the time by doing this). If it does die, the second time you start it it’s fine. Once running there are no problems. This started after the first battery change (about 3 years ago), but now it is on it’s 3rd battery and is still acting up.

If you break this into three paragraphs, with three main subjects, I may try to help you. As it is, it’s is too mixed to do anything with.

I doubt that the battery is a factor.

It sounds to me like you either have a bad temp sensor, wo when the engine is cold the ECU is unaware of it and does not make the proper adjustments (increased injector pulsewidths) or, more probably, you’re haing difficulty with fuel pressure or with the fuel draining back into the tank when the engine is shut down.

The fuel line works like a drinking straw. If you a sealed system the fuel will stay in the line and immediately repressurize when the pump is started. If you have a path for air to enter, such as a leaky injector, the fuel can drain back down into the tank as the car sits. It will then have to refill and repressurize before running properly.

Is the temp sensor controlled by the ECU or is it part of the ECU? Obviously I don’t know what I am talking about : ). But from your comments one possibility is a bad temp sensor, as for the fuel draining back into the tank, what is failing there that needs reparing if that in fact is the cause?

The temp sensor is controlled by the coolant temp, and reports values to the ECU. It is not part of the ECU and is a fairly cheap and easy thing to replace in most cases.

Fuel draining back into the tank is normally from a bad check valve at the fuel pump.

One thing you can do to find out about about this is to turn the key to start, but not all the way until it cranks - just till all of the dash lights come on. Listen when you do this and you should hear something hum for a couple/few seconds - that is the fuel pump. When the hum stops turn the key back off, then to start without cranking again. Do that a few times and then fire it up. If this problem goes away then this fuel pressure bleed is a good bet. BUT - as it is an intermittent problem it will be hard to say when to call this testing done. The more straightforward approach is to put a fuel pressure gauge on it, measure the drain down and the pressure produced by the first cycle of the fuel pump.

I will toss out one other possibility which is perhaps the first signs of a sticky idle air control valve (IAC) - this is the thing that controls the idle and consists of a little ECU controlled motor and pintle that opens to varying degrees to control the amount of air going into the engine at idle. The internals get gunked up over time and if the pintle sticks will cause idle problems. Yours would obviously not be bad - yet. A new IAC is usually not cheap - but cleaning an existing one is cheap and easy.

It works like this: The engine coolant temperature sensor sends a message (actually a voltage) to the engine computer (ECM) telling it what the engine temperature is. The ECM sends a signal (a choppy voltage) to the idle air control valve (iacv) to make it open the intake bypass air a certain amount. In your case the iacv responds as it should, or, maybe it doesn’t. Your mission: find out.
The repairs manuals tell how to do ohm and voltage checks on these components.

This started after the first battery change (about 3 years ago), but now it is on it’s 3rd battery

Three batteries in three years???   Let's start there.  Why have you needed so many batteries?  If you don't know let's work on that one.  Maybe a bad charging system?

Thanks everyone. This is my daughter’s car. I think one of the battery changes was at her request because the symptoms started after the first battery change. Since she has taken it to the Nissan dealership multiple times trying to diagnose the root of the problem to no avail she thought that might be the problem. (But the other 2 batteries does seem excessive and maybe unnecessary?!?). I’ll have her pursue these suggestions here and post the results.

It has proven fruitless to take it to that Nissan dealership. Ask around (of friends, and even mechanics) for a decent independent repair shop/person.
[You could, even, download and print the responses for your prospective mechanic. Just think of it, unlike at a Nissan dealer(usually), you’ll get to meet, and speak, to a real, live, mechanic! Wow!]

Respectfully, even with a leaky check valve the fuel will stay in the line without a path for air to enter the line, just as fluid stays in a straw when you cap it with your finger. The injectors all should fully close when deenergized. However the line will depressurize immediately upon turning the engine off. Repressurization should only take a moment, though, and should not be noticable on startup.

I’m in full agreement with the rest of the post.