By on June 29, 2009

TTAC commentator Aren Cambre writes:

I have a question about my 2002 Nissan Maxima. A while back, I had the battery disconnected for a few hours. After reconnecting, the car forgot how to maintain idle right after starting: if I don’t nudge the gas pedal for several seconds after starting, RPMs fall to 0. Internet research is conflicting. Some say it will heal on its own, others say dealer-only repair.

It’s been a few months now. How do I fix this? Is it really dealer only? If I don’t fix, will I hurt the car? (I don’t mind nudging the gas pedal–kind of like when I set the carburetor choke on my ’74 Nova.)

Sajeev answers:

So it’s been a few months? Unless you cover less than five miles per month, the computer should re-learn its operating environment (and change its evil ways) by now. So I share your disappointment. Actually, I am all choked up.

The Maxima is no different then the Nova: but today we use the term “Idle Air Control Valve” instead of “Choke.” It might be a political correctness thing: perhaps choking your car leads to road rage or other violent behavior?

Whatever. Odds are a plugged or failing IAC valve is the culprit. Sometimes it will throw an engine trouble code but I’ve never been so lucky. You can try cleaning the IAC with WD-40 (or equivalent), but this is one time where throwing a part at a problem is a safe bet. After you inspect the vacuum lines, spark plugs, replace fuel filter, etc. to ensure the car is in tip-top shape, of course.

Bonus! A Piston Slap Nugget of Wisdom:

A dealer service bay isn’t normally any better than a reputable, non-franchise shop with access to electronic data warehouses like AllData. I’d wager that the dealer is the worst place to get older models serviced: only the more senior techs know the details in the design, and you won’t be lucky enough to get them working on your car. And you don’t want to know what junior mechanics think of your clunker.

Plus if you’re lucky, there’ll be a sales jockey watching you watch daytime TV and drink shitty coffee in the customer waiting area. If they don’t roll up with a “we are in desperate need of clean trade ins” at first contact, you’ll probably get a model-appropriate brochure with a business card stapled to the cover. Been there, done that and suppressed a gag reflex: vowing to never take an old car to a new car dealership ever again.

[Send your technical queries to]

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19 Comments on “Piston Slap: Choke that Maxima Edition...”

  • avatar

    Some GM vehicles will lose their “memory” and need to be recalibrated if the power has been disconnected for an extended period, maybe Nissans do to. If you’re having problems lasting several months, it might not hurt to find out if that’s the issue. An hour’s labor at the local Nissan place should diagnose the problem and if it’s just a reprogram, they should include it in the price.

  • avatar

    «A dealer service bay isn’t normally any better than a reputable, non-franchise shop with access to electronic data warehouses like AllData»

    Looks like very sound advice.

    At what point in time, would you say, do the seniormost mechanics at a dealer move on and leave the older models to the trainees? When the “All-New” comes out? But what if the “old” is simply last year’s version?

  • avatar

    That’s not a picture of a 2002 Maxima. ;)

  • avatar

    2002 is older?!?! My 1991 is older in my book!


  • avatar

    Why should the Idle Air Control give problems only on start-up and not after the car has been running for a while?

    I take it this occurs right after you turn the key, not once it’s warmed up and waiting a stoplight halfway to work.

  • avatar

    This happened to me as well when I replaced the battery on our 2004 G35x. It seemed to happen more often when the car was warm, just after starting it. It never stalled while driving. I reset the ECU and it corrected itself.

    You can probably find directions how to do this on one of the Nissan forums. Every model is different and there was a bunch of steps necessary to reset mine.

  • avatar
    Daniel J. Stern

    @NBK-Boston: Why should the Idle Air Control give problems only on start-up and not after the car has been running for a while?

    For the same reason automatic chokes used to stick open before the first cold start of the day: gummy gasoline residue would glue the choke pull-off piston to its cylinder wall when cold, but wouldn’t have the adhesion to to so when warm. The fix was to flush the pull-off piston and cylinder with carburetor cleaner, and the solution was Chrysler’s 1964 replacement of the piston-and-cylinder arrangement with an external vacuum pull-off diaphragm pot.

    IAC motor pintles and the associated throttle body air passages do want cleaning from time to time; more so on some engines than on others—this is a relatively cold part of the intake tract, so over time, gasoline condensates accumulate. WD-40 is not an appropriate pick for this (or much of any other) job; the throttle body cleaners intended for the task work much better.

  • avatar
    cRacK hEaD aLLeY

    A Maxima with Alzheimer’s. What’s next? An Explorer with weak shocks? Incontinent Yukons??

  • avatar

    As an owner of a handsome 2002 Maxima, I must say your incorrectly used photo of a 2004-2006 Maxima wounds me greatly with it’s ugliness.

  • avatar

    This may be a dumb question, but when you were working under the hood did you by any chance knock off a vacuum line on the intake side? This would cause exactly your symptoms. (btdt)

  • avatar

    Whenever I have to disconnect the battery I jump a spare battery to the cables so I dont have to reset the clock and radio and wait for the cumputer to straighten out.

  • avatar


    Whenever I have to disconnect the battery I jump a spare battery to the cables so I dont have to reset the clock and radio and wait for the cumputer to straighten out.

    Wait, doesn’t that invalidate the reasons to disconnect the battery?

  • avatar

    Many cars clear out the evaporate emissions canister when started. This pulls fumes from the charcoal can into the engine for a few seconds. The relay could be stuck or the valve dirty. Usually happens only on startup.

    Check to see of you have a vacuum line going to a valve that goes to the evaporation can.

  • avatar

    All, thanks for the responses!

    Cold and hot starts are bad. But small correction to my words: cold start = better likelihood of catching without pedal input, but RPMs still dip to 500 or less before recovering to normal cold idle speed.

    NBK-Boston: Once started, idle is fine. Only problem is starting, nowhere else.

    rtt108: Haven’t needed to mess with anything yet. Don’t recall anything around battery related to vacuum, but will check.

    I hear all of you on IAC, but why would IAC problems only crop up after battery disconnection? This was night-and-day: car started fine before battery disconnect, but after after have to nudge pedal to start.

    BTW, a picture of it is at (Sajeev, fine with me if you want to use it, just don’t hotlink. :-))

  • avatar

    GS650G: That’s interesting. In 2004-2007 I occasionally got vacuum canister purge valve codes, but they haven’t come back since then. Maybe it’s time to finally replace? I think it’s front center of engine?

  • avatar

    Vacuum hoses is a good tip, also check where each part of the intake connects from the air filter through to the throttle body. The last shop I took my car too actually put the air intake on wrong, it looked fine from the top but underneath the intake was pushed in and not on the outside of the throttle body like it should’ve been. That was causing an irregular idle. What were you working on to have the battery disconnected? That’s what I would check first.

  • avatar

    I checked around the engine compartment when I got home and saw no sign of loose vacuum hoses.

    dolo54: I was just replacing the battery. No other work. I probably just had the battery out for too long?

  • avatar
    Jeff Puthuff

    Aren, here is a tutorial on cleaning the Idle Air Control Valve (IACV) from Nissan/Infiniti Car Owners (NICO) club. If you have any questions, the Nissan Tech Forum is a good place to get support.

    When you restarted the car after replacing the battery, did you drive around for at least five minutes, or start it and cut it?

    I would reset the ECU before throwing any parts or labor at it.

    How to reset ECU in 5th and 6th Generation Maximas

    1. Turn ignition switch on and wait about 3 seconds.

    Repeat the following steps (2a and 2b) procedures quickly—five times within 5 seconds.

    2a. Fully depress the accelerator pedal (HARD).
    2b. Fully release the accelerator pedal.

    3. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 10 seconds until the CEL starts blinking.
    4. Fully release the accelerator pedal (while the CEL is still blinking)
    5. Wait about 10 second.
    6. Fully depress the accelerator pedal and keep it for more than 10 seconds.
    7. Fully release the accelerator pedal (The CEL light will continue to blink).
    8. Turn ignition switch to “OFF” position.
    9. Now start the car. The CEL light should be off.

  • avatar

    Jeff Puthuff: Thanks. Would disconnecting the battery overnight also reset the ECU? I did that a couple of weeks ago experimentally–thinking that after the first battery disconnection, something may have gone nutty and a second battery disconnect may clear everything.

    I drove for about 15 minutes after reconnecting the battery the latest time.

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