1996 Deville...... 4.6 Northstar trouble......lotsa trouble.
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Northstar Engines and System Technical Discussion Discussion, 1996 Deville...... 4.6 Northstar trouble......lotsa trouble. in Cadillac Engine Technical Discussion; Hello, it's me again! I have a 96 Deville 4.6 that I just can't seem to get it to pass ...
  1. #1
    ralphieboy57 is offline Cadillac Owners Member
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    1996 Deville...... 4.6 Northstar trouble......lotsa trouble.

    Hello, it's me again!I have a 96 Deville 4.6 that I just can't seem to get it to pass smog here in California. I have replaced THE PLUGS, PLUG WIRES, FPR regulator, Intake manifold gaskets, anti backfire valve, air filter, oil change. After I did the intake manifold anti backfire valve, it started right up and ran good for a few days and now it runs real bad and eats gas like crazy, and it hesitates on acceleration. Hard to start hot or cold. Here are the codes it now throws.

    P1406- is an EGR pintle position problem.

    P0108- Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage.

    P0151- HO2S Circuit Low Voltage

    P0300- Engine Misfire Detected.

    What would cause all this to happen? Did I do something wrong? Im about ready to give this car away or junk it but I got too much $$$ into it and I am just too suborn to not finish the job I set out to do. I consider myself a expert Auto mechanic and have never had a car stump me like this one. Any help would be appreciated.

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    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
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    Judging by the codes...

    A sticking EGR valve, a faulty MAP sensor (or problem in the circuit), and a faulty O2 sensor (or problem in the circuit).

  4. #3
    rodnok01's Avatar
    rodnok01 is online now Cadillac Owners Connoisseur
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    Re: 1996 Deville 4.6 Northstar trouble......lotsa trouble.

    Did you use AC 41950 plugs? Clean the TB?
    I'd be poking around looking for another vacuum leak also if codes don't lead to a fix.

  5. #4
    The Donald is offline Cadillac Owners Fanatic
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    Re: 1996 Deville 4.6 Northstar trouble......lotsa trouble.

    Quote Originally Posted by ralphieboy57 View Post
    Hello, it's me again!I have a 96 Deville 4.6 that I just can't seem to get it to pass smog here in California. I have replaced THE PLUGS, PLUG WIRES, FPR regulator, Intake manifold gaskets, anti backfire valve, air filter, oil change. After I did the intake manifold anti backfire valve, it started right up and ran good for a few days and now it runs real bad and eats gas like crazy, and it hesitates on acceleration. Hard to start hot or cold. Here are the codes it now throws.

    P1406- is an EGR pintle position problem.
    Ive got a 98 Deville, put thousands into it and it keeps popping codes I'll drive it till it quits then I'll junk it. No more old high mileage cars of anykind for me. I wouldnt buy a Cadillac unless it was at least a 2010.

    P0108- Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage.

    P0151- HO2S Circuit Low Voltage

    P0300- Engine Misfire Detected.

    What would cause all this to happen? Did I do something wrong? Im about ready to give this car away or junk it but I got too much $$$ into it and I am just too suborn to not finish the job I set out to do. I consider myself a expert Auto mechanic and have never had a car stump me like this one. Any help would be appreciated.
    You bought an old Cadillac.. I wouldnt touch one of these unless it was at least a 2006 or better yet 2010 (ask me how I know) my 98 Deville has me broke and it's still popping codes I'll drive it till it wont go anymore and then I'll junk it but I'm not putting any more money in this disaster.

  6. #5
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: 1996 Deville 4.6 Northstar trouble......lotsa trouble.

    Let's move this down to Engines, Northstar. Down there, you might get more engine diagnosis than here in Deville.

  7. #6
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    Re: 1996 Deville...... 4.6 Northstar trouble......lotsa trouble.

    Seems pretty obvious to me. Clean the EGR valve, replace the MAP & O2 sensor and clean the TB if you didn't do it when you had the manifold off. After that you should pass with flying colors.

  8. #7
    ralphieboy57 is offline Cadillac Owners Member
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    Re: 1996 Deville...... 4.6 Northstar trouble......lotsa trouble.

    Quote Originally Posted by Ranger View Post
    Seems pretty obvious to me. Clean the EGR valve, replace the MAP & O2 sensor and clean the TB if you didn't do it when you had the manifold off. After that you should pass with flying colors.
    I did clean the throttle body. But EGR, no it wasn't cleaned. That will be my Monday afternoon project.

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    Quote Originally Posted by The Donald View Post
    You bought an old Cadillac.. I wouldnt touch one of these unless it was at least a 2006 or better yet 2010 (ask me how I know) my 98 Deville has me broke and it's still popping codes I'll drive it till it wont go anymore and then I'll junk it but I'm not putting any more money in this disaster.
    Bottom line your right. But if that was the norm there wouldn't be any of those beautiful classic cars you see from time to time on the road. The old Devilles are a testament to what America is all about.

    ----------

    Again, thank you all who take there time to answer questions from people like me. Your wisdom and knowledge about these cars is priceless.

  9. #8
    Tailfin's Avatar
    Tailfin is offline Cadillac Owners Enthusiast
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    Re: 1996 Deville...... 4.6 Northstar trouble......lotsa trouble.

    I agree with Ranger...those first 3 codes...the EGR valve, the O2 sensor...there are probably 2, or maybe even 3 on a California car..., and the MAP sensor...are all things that would directly affect emissions. I'd just replace them all. All that other stuff you replaced would have much less affect on emissions than what the codes are telling you.... Are you saying those codes were all not there before you did work?

  10. #9
    Ranger's Avatar
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    Re: 1996 Deville...... 4.6 Northstar trouble......lotsa trouble.

    It's a '96 so it has 4 O2 sensors.

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