MAP Sensor relocation
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Northstar Engines and System Technical Discussion Discussion, MAP Sensor relocation in Cadillac Engine Technical Discussion; Hello everyone ,I have used this site many many times for a long time ,I decided to join today ,This ...
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    packrat427's Avatar
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    MAP Sensor relocation

    Hello everyone ,I have used this site many many times for a long time ,I decided to join today ,This site has helped many time while working on my 94 Seville SLS
    I try to do all of my own work ,but I am stumped on this one
    Has onyone relocated the MAP sensor outside of the engine .
    Caddy engineers have said that my excessive map sensor failure is from excessive blow by and is messing up the sensor every 6 mos ? I have never seen any blow by or smoke out of the exhaust .
    So they say it can be relocated ,but gave me no direction and the dealer has never done one, it does leak a excessive amount of oil when you drive it hard . Maybe the blowby is what is pushing all the oil out.
    Just wondered if anyone had relocated one or had the same problem

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    chevelle is offline Cadillac Owners Enthusiast
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    Re: MAP Sensor relocation

    "Caddy engineers" have told you this....????......LOL

    There is really no reason to try and relocate the MAP sensor outside of the intake manifold. Oil leaks or "blow by" shouldn't cause a MAP sensor failure.

    What sort of MAP sensors are failing? Are they OEM factory parts or an aftermarket part?

    It is entirely possible to mount the MAP sensor outside of the intake manifold. You would have to route the wiring harness to the MAP sensor from the intake to the outside and connect the MAP sensor to the intake manifold vacuum via a vacuum hose. Then it would work just like it does inside the manifold....and it would be connected to the intake manifold with the hose just like it is today...

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    1993 eldorado green1's Avatar
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    Re: MAP Sensor relocation

    i agree with chevelle, if the map sensor is failing like that then either a your using a cheap part or b it is not seating all the way down when installed.

    the only reason i can come up with as for the fialing is if your vacume lines have too much oil in them and its trying to pressurize the map sensor.

    when a non turbo/supercharged engine is running at idle the motor creates vacume, at W.O.T it actually goes to zero vacume. if your getting oil in the vacume lines then its possibly time for new rings or you have a plugged pcv system.

    relocating the map somewhere else is not gonna help you at all if you are having a problem with oil in the vacume lines...

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    packrat427's Avatar
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    Re: MAP Sensor relocation

    They are all factory parts , I would think ,the last 5 have been under warranty,I paid for the first one about 3 years ago and They have failed on a average of every 6 mos. They had called tech last time wondering why so many ,This time they called, and one of the engineers had said that the sensor was pulling the oil in and causing it to fail ,I guess that they have had several with this , but he said it was from the blowby,and this one would not be covered under warranty since they knew what was causing it now ? The Engineer said that there was a way to relocate it on the outside ,you would need to modify the harness ,but the dealer said that they had never done one , I guess with the sensor being farther away from the source it would not let it be directly exposed to the oil up thru the extended line that it would require to hook it all up.
    The MAP sensor values are all over the place when it starts acting up ,causing it to surge ,RPM to flare or drop ,and it has died ,it has always been the map sensor, and it has always fixed it .

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    1993 eldorado green1's Avatar
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    Re: MAP Sensor relocation

    Quote Originally Posted by packrat427
    They are all factory parts , I would think ,the last 5 have been under warranty,I paid for the first one about 3 years ago and They have failed on a average of every 6 mos. They had called tech last time wondering why so many ,This time they called, and one of the engineers had said that the sensor was pulling the oil in and causing it to fail ,I guess that they have had several with this , but he said it was from the blowby,and this one would not be covered under warranty since they knew what was causing it now ? The Engineer said that there was a way to relocate it on the outside ,you would need to modify the harness ,but the dealer said that they had never done one , I guess with the sensor being farther away from the source it would not let it be directly exposed to the oil up thru the extended line that it would require to hook it all up.
    The MAP sensor values are all over the place when it starts acting up ,causing it to surge ,RPM to flare or drop ,and it has died ,it has always been the map sensor, and it has always fixed it .

    i would still check the pcv system and "seafoam" the engine to possibly clean the valves/top piston rings and see if that helps.. i had a issue with oil burning when at idle, it would smoke so badly that you couldnt even see out of the rear window when i would take off. i did the seafoam treatment through the vacume lines and it solved my problem.

    i would think that if your northstar had that much blow by then it would be using alot of oil between oil changes. does it?

    possibly try another dealership, where did you take the car that they told you about this map sensor problem?

    where did you buy the original map sensor from??

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    parts68 is offline Cadillac Owners Fanatic
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    Re: MAP Sensor relocation

    My 78 Seville (which was a Beta version of an FI car) has the MAP
    located next to the PCM which is underneath the ashtray in dash.
    A long nylon tube connects it.
    I would think this proved to be undesireable as it takes too long for the MAP to react to changes in engine vacuum.

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    Re: MAP Sensor relocation

    I own stock in Seafoam products ,LOL .. I use it religiously in all my cars ,I pour it in the intake tube ,I pull off the hose on the brake booster ,and one other line on the T/B and feed it all thru there then shut it off for 15-20 min and then watch her smoke like a freight train going down the road .
    It had a code the very first time for the map sensor along with another code ,I don't have them handy it has been almost 3 years .
    I had all the work done at a Cadillac dealer the first time for it ,and all the others were covered by the GM warranty, because it was less than a year, I hope they were all GM parts .
    It leaks oil but I have never seen a hint of smoke out the exhaust or anything that resembles blowby with the oil fill cap off it has the normal oil pan leak.
    As for the dealer it was done by is the oldest Family owned Cadillac dealer in U.S. ,it was Tallman Cadillac here in Decatur ,Il. over 100 years ,they just sold it in last 6 mos. I just thought I would throw that in

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    Re: MAP Sensor relocation

    Well I just got the car back today ,and I found out something with a some value ,some of you may already know ,cadillac has known of this problem for a long time ,not all Northstars are going to do this ,especially if properly maintained and not given the chance to carbon up.
    But the stuck rings that cause most of what is going on in my situation,(blowby) that fail the MAP sensor ,Cadillac has a special tool that has a special injector that sprays a solvent in a cone pattern into each cylinder, because of the cyl.angle ,they don't just pour it in,and they do this 3 times to decarbonize the rings to break it up and help create more tension between the ring /cylinder wall .
    I was not aware of this machine that Cadillac has issued to dealers to help deal with this .
    So my theory is that there is alot of these cars running around out there unsuspecting , that need decarbonized ,
    The origional owner must have babied this car because when I first got it ,I replaced the EGR valve ,and had to have all the EGR ports in the head cleaned out which had over 2 handfulls of carbon cleaned out , All of the ports were clogged up and was pulling vac on 1 cylinder ,and was creating a feeling of a miss under light load , more often when it was in OD. at 45 mph .
    Sorry for the long post , but I thought I would share this.

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    parts68 is offline Cadillac Owners Fanatic
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    Re: MAP Sensor relocation

    I would do top engine cleaner soak followed by the water injector trick

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    Re: MAP Sensor relocation

    I can do a top end clean ,but you lost me on the water injector trick , and how do you do the soak with the angle of the cylinder and the solvent running to the bottom of the cyl. Thanks .. Doug

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    parts68 is offline Cadillac Owners Fanatic
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    Re: MAP Sensor relocation

    yea its really not that easy to soak a V shaped engine.
    I make sure that the piston is down alittle in cylinder
    and spray it in with one of those large syringes used for
    measuring 2 cycle oil.
    If you put the clear tube on the end of syringe it will fit
    in spark plug hole.
    You also remove the injector and squirt in there.
    The instructions say soak for 30 minutes but I leave overnight.
    Suck out all the excess,turn engine over by hand to blow out
    thru the spark plug holes,reinstall injectors and plugs,fire it up and run at high idle.
    warm engine up and make sure you dont have to shut it off for 30 minutes.
    after warm up get a squirt bottle or even a large type ketchup bottle,filled with plain water.
    Slowly squirt into the throttle body but never choke the engine down and keep revs high enough to avoid stalling.
    run engine for 15 minutes after a bottle of water,change engine oil& filter.
    This is probably not something the average DIY should do but if you feel comfortable enough do so.
    Minus is that if done wrong you can break or ruin something.
    Ive decarbonized many an engine with this procedure that would otherwise
    need heads removed.
    Its like steam cleaning the inside of combustion chamber.
    Next step is to blow it out with a few 6K blasts.
    Your N* needs to be excersized like a pure bred race horse

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    Re: MAP Sensor relocation

    10-4 Gotcha , I will try it soon ,that all sounds familiar ,what the dealer said , spray it with the machine ,let it soak overnight , and then suck it out ,then run it ,and they do this 3 times he said . I would like to have access to that machine some weekend !!
    I never give mine a break , I think alot of the problems occured before I got it , even the manual suggest 2nd gear accel,decel to help keeping it cleaned out ,but the last time I done that it threw 2 codes ,but I cleared them . Thanks again.. Doug

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    parts68 is offline Cadillac Owners Fanatic
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    Re: MAP Sensor relocation

    WOT is your friend

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    Re: MAP Sensor relocation

    We are more than friends ,we are related I have never babied it !
    I am going to try some things this weekend ,I use the seafoam all the time ,but I am going to do a more saturated top end clean this time ,maybe multiple times to help free up the ring's and grooves to see if that helps. I will try your procedure soon ,it is so close to what the dealer does with the machine. Thanks...Doug

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    parts68 is offline Cadillac Owners Fanatic
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    Re: MAP Sensor relocation

    Use GM top engine cleaner not seafoam

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