Nov 222009
 

Had the crank position sensor replaced new in my 1993 plymouth laser. Several times now engine turns over but does not engage. After getting it towed to garage it would start up! Can the new sensor be faulty and work intermittently? Could it be the engine control module? Had the fuel pump checked but it is fine. Also had the fuse box next to battery terminal replaced

  8 Responses to “1993 plymouth laser Engine turns over but will not start”

  1. You first need to find out what it isn’t getting.
    1. Spark
    2. Fuel
    3. Injector Pulse
    4. Correct Timing
    5. Compression

    http://www.freeautomechanic.com/nostart.html

  2. Thanx for your suggestion but as you know the items you listed above all check out when the car is running but..

    I want to avoid having to pay for towing the car again as it has happened twice since the Crank Position sensor was replaced. The mechanic says all that can be done is wait until the problem manifests itself again but this means I have to leave the car at the garage for who knows how long. Last time it took 2 weeks before the car wouldn’t start

    So guess what I’m hoping for is another opinion as to what the problem “might be”

    When mechanic first identified the initial problem it was the crank position sensor. Assuming the new one is OK what else could it be that works intermittently. Can either the ignition coil, ignition switch or ECM work intermittently or something else? Trying to narrow it down as best as possible. For example if only the ignition switch could possibly work intermittently then I would chance it and replace this item but if any of the 3 mentioned or more could work intermittently then I would wait until the problem occurs again as it is expensive. If practical I want to avoid having to wait for the problem to happen again.
    If possible Your best guess and advise regarding whether any of the items I mentioned could work intermittently would be much appreciated

    Again, Thanx

  3. In this case the only way to know for sure is to wait until it won’t start. Testing anything when it runs will test good as you already know. There are too many possible causes to start throwing parts at it. The best thing is to do as your mechanic has suggested and wait for it to happen again.

    An ignition module is the most common failure part for this, but it is best to make certain if you want it to be a reliable fix.

  4. Much Appreciated Jaxer

  5. Car finally failed and diagnosed as bad PCM (ECU). Found a used one and had it replaced. Car working fine now except the manufacturer specifications say the Idle should be at no more than 850 rpm when engine warm and transmission in neutral. However the idle rpm is 1100 at best and the idle adjustment screw is turned to its maximum. When transmission is in drive (and engine warm) it should idle at around 650 at full stop as it used to but now it idles at around 800. At cold idle the RPM is 2200, much higher than before.
    I can wait until the engine warms before shifting out of park otherwise getting a hard knock. This can’t be good on the transmission.
    Now my gas mileage has worsened.
    Advise/suggestions would be greatly appreciated. What could it be (Oxygen sensor? Replaced PCM?).
    Mechanic is miffed. No diagnostic codes showing up.
    You should probably know that a few months ago the rpm would fluctuate up and down during cold starts. Had the throttle body replaced with a used one which eliminated the problem.

  6. Car finally failed and diagnosed as bad PCM (ECU). Found a used one and had it replaced. Car working fine now except the manufacturer specifications say the Idle should be at no more than 850 rpm when engine warm and transmission in neutral. However the idle rpm is 1100 at best and the idle adjustment screw is turned to its maximum. When transmission is in drive (and engine warm) it should idle at around 650 at full stop as it used to but now it idles at around 800. At cold idle the RPM is 2200, much higher than before.
    I can wait until the engine warms before shifting out of park otherwise getting a hard knock. This can’t be good on the transmission.
    Now my gas mileage has worsened.
    Advise/suggestions would be greatly appreciated. What could it be (Oxygen sensor? Replaced PCM?).
    Mechanic is miffed. No diagnostic codes showing up.
    You should probably know that a few months ago the rpm would fluctuate up and down during cold starts. Had the throttle body replaced with a used one which eliminated the problem.

    Sorry If I posted twice but not sure whether I did this right the first time

  7. Usually a flutuating idle is related to bad IAC or a vacuum leak. A higer idle than normal would cause me to lean toward a vacuum leak, as this would also force the engine to need more fuel and cause your fuel mileage to get worse.

  8. The idle isn’t fluctuating, it’s to high on cold starts (2200 rpm) and also when engine warmed (800 rpm should be 650) . I was wrong about the gas mileage. Its better, forgot about how much the car had been running (while parked). Checked the actual mileage and it is fine. Fairly certain the IAC is attached to the throttle body or am I mistaken? The throttle body was replaced with a used one 2/3 months ago because the idle was surging/fluctuating when starting up the cold engine. If not in the throttle body where would it be? Can I remove & clean it and if so how does one clean this or would it be better to get it replaced.
    I do notice a faint hiss when I lift the hood and get my ear real close. It’s where the hose for the PCV Valve is situated. Checked the hose and it is fine. Plugged and opened it see if this would change the idle, nothing.
    My gut tells me the PCM needs to be replaced. Expensive to rebuild, hope I’m wrong.
    Thanx for all your advise,

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