Plenum Issue??? AIR system issue ???
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Northstar Engines and System Technical Discussion Discussion, Plenum Issue??? AIR system issue ??? in Cadillac Engine Technical Discussion; Hello everyone. I have developed a slightly rough idle on my 02 Deville. I don't have any codes other than ...
  1. #1
    TheC.Hicks's Avatar
    TheC.Hicks is offline Cadillac Owners Member
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    Plenum Issue??? AIR system issue ???

    Hello everyone.

    I have developed a slightly rough idle on my 02 Deville. I don't have any codes other than the p0410 which I am about to get fixed.
    The SES light is on because of the p0410 code obviously, but I've noticed that when I do a WOT or drive uphill, the light flashes and there is a very slight hesitation. Could this be plenum related or would the p0410 cause this?
    I used some Techron the other day and I noticed some improvement. Good stuff...

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  3. #2
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Plenum Issue???

    Secondary AIR won't cause a rough idle - the fresh air goes to the exhaust manifolds, nothing ahead of that.

    Check the usual litany of items: Air filter, air ducting for leaks at/after the MAF, MAF electrical connector, throttlebody cleanliness, PCV system tight with no vacuum leaks, fuel injector electrical connectors tight and clean, FPR and its vacuum signal hose not leaking raw fuel, fuel pressure check (test gauge from auto parts store) - the test port on the fuel rail - looks like a tire valve and cap - 40+ psi at idle.

    Plugs/boots/coil cassette ICM connectors ?? A flashing SES is "severe misfire". A couple of cylinder ignition or fuel injector problems causing rich fuel mixtures WILL damage the catalytic converter and that WILL cost you a real bundle to fix. If the car has over 80,000 miles, is a city driver, or is not driven in a "spirited manner" once in a while, plugs would be suspect. AC Delco #41-987 Platinum ONLY, Don't fall for cutesy boutique plugs and don't let some shop talk you into "These Autolites are just as good". I know it sounds like black magic, but it's true.

    A split plenum usually sets P 0171 and P 0174 (lean mixtues, Bank 1 & 2).

  4. #3
    TheC.Hicks's Avatar
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    Re: Plenum Issue???

    Thanks Submariner. It's interesting because I originally changed the front coil cassette and all the plugs, yet as soon as I started the car, I got the p0410 code. The rough idle started over time. I assumed it could be fuel related, so I will check that out in addition to the other stuff you mentioned.

  5. #4
    Ranger's Avatar
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    Re: Plenum Issue???

    Quote Originally Posted by TheC.Hicks View Post
    The rough idle started over time.
    Try cleaning the TB as one of the things Sub mentioned. That's something that people forget and can cause a rough idle.

  6. #5
    Submariner409's Avatar
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    Re: Plenum Issue???

    The P0410 - Go through the AIR vacuum control solenoid - right next to the right (rear) AIR control valve at the fuel rail level - and trace out the vacuum lines/pipes. Those little plastic pipes tend to get brittle and can crack so you can't see the break. Any plastic vacuum line on that engine can be replaced with a suitable length of proper sized vacuum hose from the Help! racks at any large parts store. A NAPA store has miles of different sized vacuum hose. Got a busted connector or Y junction ?? Also on the Help! racks.

  7. #6
    TheC.Hicks's Avatar
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    Re: Plenum Issue???

    Thanks Ranger. The TB is my project for today.

    Submariner, I figured that the hoses were probably cracked. I checked the fuses and there was not a blown fuse and I still hear that vacuum cleaner sound on a cold start.
    That rear AIR control valve that you speak of, is that the thing over the rear coil cassette???

  8. #7
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    Re: Plenum Issue???

    Yep, the right AIR valve is bolted to the bracket on the cam cover.

    Depending on your car's emissions calibration, the ambient temp, phase of the moon and how many virgins you have sacrificed you WILL hear the AIR system compressor once in a while. If it is more than a distant whine the chances that the air intake cover for the compressor (pump) has fallen off. Up inside the LF fenderwell liner - car on jackstands, remove the wheel and well liner. Many posts and pictures by Ranger and others on the cover repair/replacement. Google something like "cadillac forums deville secondary air pump" or something close.

    Look on the right (passenger) strut tower - depending on how many AIR pumps your particular year/model has there will be 0, 1, or 2 gray relays clipped onto a metal bracket on the strut tower.

    AIR noises or codes aren't related to a rough idle.

  9. #8
    Ranger's Avatar
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    Re: Plenum Issue???

    If you are hearing the "vacuum cleaner" sound, I'd bet the intake cover has come loose (#9 and/or #8).



  10. #9
    TheC.Hicks's Avatar
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    Re: Plenum Issue???

    Ah you guys are the best.
    The rough idle subsided after I cleaned the throttle body and put in a new air filter yesterday evening. There's still a very slight (almost unnoticeable) roughness. I'm gonna do a bit more looking tomorrow after I have my buddy do my control arms and tie rod ends (yay).

    Where should I be looking for this intake cover? Is it a matter of simply tightening it or replacing it??


    Thanks for all your help Ranger and Submariner.

  11. #10
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    Re: Plenum Issue???

    The AIR compressor cover/silencer ????

    Already posted in text and diagrams Posts 7 and 8.

    P0410 (Is it Current or History ??) is a sort of catch-all for the system - 0411 to 0419 define specific parts.

    If the cover is destroyed (excellent chance, just ask Ranger) it's a junkyard item. If the whole system is dead, you need to begin at the compressor and diagnose the entire system, including relays, vacuum lines, and AIR valves (2) - one on top of the right (rear) cam cover, one just next to the "lower" radiator hose on the driver's (transmission) end of the engine.

    Otherwise look in www.gmpartsgiant.com or wait and talk to Chris in parts at Rippy Cadillac over there >>> on Tuesday morning, EDT

  12. #11
    TheC.Hicks's Avatar
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    Re: Plenum Issue???

    Ah I see. I got a little confused. I'm gonna check it out momentarily.

  13. #12
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    Re: Plenum Issue???

    ...and the p0410 is current.

  14. #13
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    Re: Plenum Issue???

    Thanks for your help, guys. Got the problem fixed. It was a bad valve...the rear one. Went and passed emissions test immediately!

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    Re: Plenum Issue??? AIR system issue ???

    Hey all you "looky loo's". I've been helped so much from this website. Cleared my P0410 code with a little effort and a lot of info from Sub 409.
    So if that's your experience, then donate to the cause. These file servers don't run on love. Just put in some cash and pay it forward for the next guy..

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