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2001 740i Starts and then while idling dies after 15 sec

Discussion in 'E38 (1995-2001)' started by kdn32303, Dec 6, 2008.

    kdn32303 guest

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    Hey everyone,

    So I have a little problem... I have a 2001 740i Sport and when I start the car it starts with no problem, but while idling it dies after about 10-15 seconds... the RPM goes up as it would when it starts, then it just goes down and dies.... any ideas as to what this might be.

    Im now living int he sticks and would like to see if I can take care of this little issue on my own.

    thanks:confused:

    kdn32303 guest

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    Does this sound like it might be the camshaft sensor (CPS) ?
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    mooseheadm5

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    It could be, but without being able to check the codes, you are sunk. First thing is to check for any massive vacuum leaks, like the intake boot or one of the idle hoses cracked. Other than that, it is really hard to say.

    kdn32303 guest

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    How would I go about checking for a vacuum leak? Today the car hasnt died, but it just seems to struggle... shakes... esp when the car is put into drive... I havent actually driven it...
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    mooseheadm5

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    <warning, do this at your own risk>
    If you can get the car to run, you can try to spray carb cleaner at all areas where you suspect there may be a vacuum leak. You may want to remove the top cover on the engine first so you can see it all. IIRC that year has the little buttons you have to press down while pulling up on the cover. Anyhow, with the motor running, you can spray a little carb cleaner at the intake boot, the back of the intake (this is the breather separator that often goes bad), the actual intake ports where the plastic intake meets the heads. If the idle picks up and smooths out at all, then you have found a vacuum leak. This is because the carb cleaner acts as extra fuel for the unmetered air going into the intake. Fixing anything other than the intake boot, or a hose at the back of the intake (there is also a little rubber cap at the back that can split and cause problems) will require tools and skills you may not posess, but finding if there is an intake leak is the first step.

    kdn32303 guest

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    I am definately going to take a look at your recommendations. What do you think about the possibility of having gotten some bad gas? I did just get gas the day before the problem started....
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    mooseheadm5

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    That is always a possibility. Since you said that, also check that your gas cap it tight.

    kdn32303 guest

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    Yea im not thinking its gas... I ordered new camshaft sensors, they are going to be in today... so im going to keep my fingers crossed that its something simple.
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    mooseheadm5

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    I hope for your sake that is the problem, but it is a shot in the dark at best. I also hope you ordered genuine BMW cam position sensors, as I have seen about a dozen aftermarket ones DOA or fail within a month.
    I will tell you it is not wise to attempt to fix a problem for which you have done no diagnostics by simply loading up the parts gun and firing it. That gets really expensive really fast if you miss. If you plan to keep working on this car to "save money" you should at least get some sort of QUALITY code scanner for BMWs. If you had one, you would instantly be able to read the codes and learn if, in fact, you need cam position sensors. Don't mean to sound harsh, just giving you the info I have learned after years of being a BMW tech.

    kdn32303 guest

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    Interesting development... The problem is that I just moved out to the sticks in TN and the closest place I can bring my car to is over 100 miles away... But I put in the new cam sensors and that didnt help... The car starts, the RPM goes up like normal and then the engine just dies... but... If i unplug the MAF thing, the sensor, when its unplugged it doesnt die... plug it back in... and it dies... does this make any sense?
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    mooseheadm5

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    Yes, that MIGHT mean that you have a bad MAF sensor, but it is not a 100% guaranteed test. You really really really need to scan the codes on that thing. Even a generic OBD2 scanner is better than nothing at this point. With the MAF unplugged the car is going by a guess lookup table for fuelling and will note that the MAF is not sending a signal. Right now, I can 100% guarantee that if you scan for codes that you will find a code for the MAF because you unplugged it, but don't know what else you will find.

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