Intake full of sludge/Intake removal
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Northstar Engines and System Technical Discussion Discussion, Intake full of sludge/Intake removal in Cadillac Engine Technical Discussion; I have a friend with a 96 Deville and it has probably 1/4" to 3/4" sludge inside the intake. I ...
  1. #1
    N0DIH's Avatar
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    Intake full of sludge/Intake removal

    I have a friend with a 96 Deville and it has probably 1/4" to 3/4" sludge inside the intake. I need to get it off to clean. I looked searched and didn't find much on intake removal (try a search for that, it is insane).

    Any advice/tips? It looks like it should be quite easy, is it?

    I don't have a N* FSM so I am at a loss on that.

    Thanks!

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    Re: Intake full of sludge/Intake removal

    The proper cleaning procedure is some high RPM operation at WOT. That sludge is the heavy ends of the fuel and oil molecules that come back through the PCV system, etc. It will stay cleaned out with enough "proper" engine operation (run it baby!). No need to remove the intake and clean that out.

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    JimD is offline Cadillac Owners Connoisseur
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    Re: Intake full of sludge/Intake removal

    What you are probably seeing on a high mileage engine is simply a buildup of unburned PVC gases, soot from exhaust gas (EGR), and fuel vapors that are present each and every time the engine is shut off and allowed to cool to ambient.

    This accumulation should be cleaned from the throttle body bore and blade perimeter every year or so to prevent off-idle throttle stickiness.

    But there is no benefit from making the entire manifold squeaky clean; the buildup will return in short order. Unless you have another reason to remove the manifold, forget it.

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    Re: Intake full of sludge/Intake removal

    This is BAD though, HARD to get out with screwdrivers scraping it and pulling it out. I probably pulled 6-8 oz of crud within 6 in of the TB. TB is clean at least. But the manifold is NASTY all the way in.

    How bad? FPR vacuum port is not able to be cleaned without intake removal, no vacuum at all, I had to get vacuum from another source. It looks like a quaker state engine intake valley of a 400M Ford....

    So what would cause that much sludge buildup? just plain lack of oil changes? The car has been fairly not taken care of. But for $1600 and it runs..... (I am thinking he should have passed on this one now....)

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    Re: Intake full of sludge/Intake removal

    the intake removal is pretty self explanitory...remove intake tubing, MAF, TB/spacer, fuel rails/injectors, remove associated vacuum lines/etc and pop off the intake...installation is reverse of removal and should go back the same way. gaskets are reusable if in good shape (per GM recommendation) but they were under 25 new for the pair from my local GM dealer so i figured wtf might as well...

    oh, the TB gasket was 7.70 from my local dealer...a litle steep but you'll need one of those too for the TB to spacer joint...

    as far as cleaning the intake? i'd soak it in some real powerful degreaser and scoop/scrape/spray out as much as you can. removing the manifold pessure valve on the rear of the intake will allow you to attack it from both ends which is A BIG HELP!!!

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    Re: Intake full of sludge/Intake removal

    So what would cause that much sludge buildup?
    Years and years of the things JimD and Jadcock mentioned.

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    Re: Intake full of sludge/Intake removal

    I just have never seen anything like it in a GM car....

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    Re: Intake full of sludge/Intake removal

    The "mistake" Cadillac made, if you can call it that, is putting an engine that is more at home at 6000 rpm than it is at 1000 rpm into cars that are driven at 1000 rpm all day. Especially the LD8 powertrains (like I had in my SLS). I could drive that car all day long, keeping up with traffic, and never break 1500 rpm if I didn't want to. The manifold design is very free-flowing (with the "tubular" design), but its design necessarily means that there are valleys in the manifold that will naturally segregate the heavy ends of the fuel and let them accumulate.

    The buildup on that engine does sound excessive...to build up so great as to plug the FPR vacuum port. I've never heard of that before, but it's apparently possible, under the right conditions. Maybe his drive cycles are abnormally short, maybe he drives it very relaxed and slow, maybe there's a mechanical failure somewhere (like a bad PCV valve, etc).

    To remove the manifold, there are only 4 bolts. And the manifold is dry, so don't drain the coolant (not necessary). Just remove/lift the fuel rail and disconnect any vacuum ports and unbolt the TB...only 4 long bolts retain the manifold to the engine. Do not buy an additional gasket -- the manifold gasket is good for the life of the engine, attached to the manifold cassette-style.

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    Re: Intake full of sludge/Intake removal

    Do you even need to take the TB off? He bought the car used and abused, now he drives it short trips too. And to make matters worse the TC/ABS is faulted (sensor I think) and won't allow 1st gear. He bought this as a second car just in case, so he doesn't want to spend big $$ getting it fixed, he just wants a backup to his Suburban. But now with gas prices so high, he is parking the Burb and driving the Cad. So we are going to try the 1K ohm resistors in the sensors to disable TC/ABS and then see if we get 1st back. That is a crappy design there, so you risk destroying the trans to get the customer to come in to the dealer.

    I hope to yank the intake tonight and see what I can do. It has had a persistant miss, PCM codes indicate #7, sometimes #8. I wonder if the sludge is interfering with an injector. I'll try to take picts.

    I put in a PCV filter in my LT1 so I don't get any oil in the intake, it works fairly well. It is from a 89 2.9L Bronco II. Maybe it can be adapted to the N*. It looks factory on the LT1, which is why I was game too.

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    Re: Intake full of sludge/Intake removal

    Quote Originally Posted by N0DIH View Post
    ...the TC/ABS is faulted (sensor I think) and won't allow 1st gear...That is a crappy design there, so you risk destroying the trans to get the customer to come in to the dealer...
    The 1st gear lockout is actually there to protect the differential. By disabling the TCS, it's easy to do one-wheel burnouts, which can heat-weld the differential spider gears and do a lot of damage.

    Post the TCS code here and let's see what the problem is. I suppose it could be as simple as the TC button in the glove box or another simple problem.

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    Re: Intake full of sludge/Intake removal

    Quote Originally Posted by N0DIH View Post
    ....It has had a persistant miss, PCM codes indicate #7, sometimes #8. I wonder if the sludge is interfering with an injector.
    You can reasonably expect the fuel spray would keep the injector tip washed clean of that black sludge. More likely is failed/failing plug wires or a cracked plug insulator.

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    Re: Intake full of sludge/Intake removal

    IIRC it was a TC0073 fault.

    I looked at the wires, they look good, and ohm out fine. Plugs are new (but I didn't install them, but new plugs didn't change anything either).

    Would the TCS being in a faulted mode cause timing to be pulled back to a point that the engine would miss? It gives a fault for it, sometimes it is bad sometimes minor. Hard to pin down. Coils ohm good too.

    Are the injectors on the N* same as any other GM engine or are they the screwy DOHC 3.4L style where they spray in dual pattern so a regular injector can't be used.

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    JimD is offline Cadillac Owners Connoisseur
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    Re: Intake full of sludge/Intake removal

    Quote Originally Posted by N0DIH View Post
    ....Would the TCS being in a faulted mode cause timing to be pulled back to a point that the engine would miss? It gives a fault for it, sometimes it is bad sometimes minor.
    Doubt if retarded (or limited advance) timing would be the problem.

    Engine power management (torque limiting) should not happen until the traction control has been active for some period of time; as in long enough to potentially overheat the brakes. And then, the torque limitation is via injector pulse width as the first step.

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    Re: Intake full of sludge/Intake removal

    As for the TC0073 code, there is a known issue with 1996 model Cadillacs where a "bug" in the software throws this code. See this thread for more details:

    http://www.cadillacforums.com/forums...0073-code.html

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    Re: Intake full of sludge/Intake removal

    There is always mention of some rear blower. I have NEVER seen a Cadillac with a rear blower from 1977-up. Where? How do you know if you have it?

    'First, turn the rear air conditioning blower to the lowest fan speed setting." Limo's have it, but not plain Deville's in my experience....

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