Edmunds Answers



  • zaken1 12/31/11 7:07 pm PST

    This kind of intermittent starting usually comes from a camshaft position sensor that is on the way out. I would replace that part; rather than waiting forever for it to set a code. A failing crankshaft position sensor could do this, too; but it is not as likely.

    A bad crank sensor will shut the spark off; while a bad cam position sensor will stop the trigger pulses to the fuel injectors. So if you find there is no spark to the plugs when it doesn't start; the crank ssnsor is the cause. If it has spark when it doesn't start; and it only fires when starting fluid is sprayed into the throttle body; the cam position sensor is bad.

  • fybg2709 01/01/12 11:02 pm PST

    So, today, it FINALLY threw a code. Mass air flow sensor...replaced it, car is running fine today...we'll see if she starts tomorrow! I won't trust her for a good long time after all this!

  • fybg2709 01/02/12 4:15 pm PST

    Ha...go figure...no start again today...nickle, dime, hundred dollar bill...can't wait to get rid of this lemmon!!

  • zaken1 01/02/12 9:04 pm PST

    Did you check for spark and see if it fired with starting fluid, like I suggested in my previous post? People pay me good money for this kind of advice, but when I give it in this forum for free; it is sometimes not taken seriously enough.

  • fybg2709 01/07/12 10:28 pm PST

    Has spark...replaced cam sensor today...it started the first time, but later wouldn't. The only way to get it to start is reset the computer with disconnecting battery completely for at least an hour. It starts that way everytime...but this doesn't seem like it could be good for it. Fuel pump sounds fine as well...open to more suggestions...$300 later and 3 weeks into this mess....good thing I don't have to pay a mechanic for 3 weeks worth of time!

    Thanks for your input so far.

  • zaken1 01/07/12 11:45 pm PST

    By disconnecting the battery, you are temporarily resetting any trouble codes that are in the computer. I say ¨temporarily¨ resetting the codes, because disconnecting the battery does not erase codes in 2003 cars. It only works in 1995 and older cars. The proper way to clear codes in a 2003 car is to use a code scanner with code clearing capabilities. If you just disconnect the battery; the old stored codes will come back soon after you start the motor. And that is why the trouble keeps coming back.

    So, since clearing old codes always makes the motor start; why not do it right, and buy and use a code scanner to get rid of those old codes permanently. It is not hurting anything to clear codes. Otherwise, there is no way of knowing whether anything you previously did has already fixed the problem.

  • fybg2709 01/08/12 1:23 pm PST

    Thanks Zaken...but that didn't work either...checking all connections again today...looking for loose, broken, poorly connected anything...someone suggested replacing IAF sensor...might do that as it's about $20...still open to any other suggestions.
    Anyone want to buy it? 3K and it's yours!

  • zaken1 01/08/12 2:33 pm PST

    Please tell me whether your car has the 4 cylinder or the V-6 motor. We need to know the engine type in order to be able to understand what is happening. I wish everyone would list their engine and car model information in their first post; but all too many people don't.

    I also need to know exactly what parts were replaced when you said "Ignition has been replaced." Did you mean the ignition switch; ignition module, ignition coils; or some other part? Also; how many miles are on the spark plugs in this car? If you've never changed the plugs; at least tell me how many years you've had the car; or how many years it has been since the plugs were replaced.

    It will be a waste of time and money to replace the IAT sensor; this part does not affect starting. But it would be a good idea to replace the fuel pump relay.

  • fybg2709 01/09/12 9:15 am PST

    It's got the v6 in it. Ignition switch replaced. We've had it for 3 years...it got new plugs before we brought it home that day. Checked fuel pressure yesterday, seemed fine at that moment. It started after we checked the fuel pressure...and again later...but not this morning.

  • zaken1 01/09/12 2:38 pm PST

    Thanks for the information. I would replace the ignition coils with either BWD #E51, or Airtex/Wells #5C1058, and also replace the spark plug cables with either BWD #CH76150 or Bosch #09362 or Standard Motor Products #7695. Please use only those brands and part numbers.

  • zaken1 01/10/12 2:22 pm PST

    Hi again; I woke up today with a new perspective on this problem. Here's a test you can do that will provide valuable information. Make sure that all electrical accessories are turned off, the key is not in the ignition, and close all doors. Then disconnect the battery ground cable and let it sit for at least 2 full minutes. Then briefly touch the battery ground cable clamp to the battery post from which it was disconnected. Watch for a spark when the cable clamp touches the post. If there is a spark when the cable clamp touches the post, then do not connect the cable. Instead, leave the cable off and disconnect the heavy power cable at the alternator. Wrap the alternator cable end in a rag, or cover the metal terminal on the end with electrical tape, so it cannot touch ground. Then try touching the battery ground cable to its post again, and see if there is a spark this time.

    If there is no spark when the battery ground cable touches its post this time; the alternator has a shorted diode. If there still is a spark this time; there is a short in the car's electrical system.

    Either a shorted alternator diode or a short in the electrical system will drain the battery when the car sits. This is why the car won't start after it has been sitting. When you disconnect the battery for two hours or more, the battery has time to recover enough to have sufficent power to start the motor easily.

    If the alternator has a shorted diode, please only buy a replacement alternator at a NAPA parts store. The reason for this is that most other parts stores sell cheaply rebuilt alternators which are not properly tested and often contain questionable used parts taken from other old alternators. There is a massive failure rate on these "rebuilt" alternators, which often leads to getting two or three defective units in a row from the store. NAPA is the only local place I know of that still properly rebuilds and tests their electrical parts.

    Alternator diodes will blow out immediately if a battery cable is ever disconnected while the motor is running. There is an old myth that an alternator can be tested by doing this; but that was only safe to do 50 years ago; when cars still had DC generators. Modern alternators produce enough power at idle that they will build up 150 volts or more when a battery cable is disconnected; the diodes can only withstand about 50 volts, so they blow when that is done.

    If there is still a spark when the test is done with the alternator cable disconnected; you'll need to pull all the fuses and relays, one at a time, from the underhood and under dash fuse blocks; and test for spark at the battery ground cable after each one is pulled. Put each fuse back where it came from before pulling the next one. When there is no spark in the test; you have found the circuit where the drain is coming from.

  • sidnoea 05/23/15 12:27 pm PST

    Sorry for pulling up an old thread, but my 2003 Grand Am is having a very similar problem where it will only start if I disconnect the computer for 15 minutes. Did you ever get a resolution on this issue? I would love to avoid buying a new PCM if I don't have to.

  • Stever@Edmunds 05/23/15 8:32 pm PST

    Since this is an old thread, try posting a new question. Might get more attention that way.


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