Hi. I need lots of help concerning the 4.9L. Thanks.
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HT4100 4.1, 4.5, 4.9 Discussion, Hi. I need lots of help concerning the 4.9L. Thanks. in Cadillac Engine Technical Discussion; Hey everyone. I hope I posted in the correct forum. I just bought a 1991 STS and I'm doing a ...
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    STSOnly's Avatar
    STSOnly is offline Cadillac Owners Fanatic
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    Hi. I need lots of help concerning the 4.9L. Thanks.

    Hey everyone. I hope I posted in the correct forum.

    I just bought a 1991 STS and I'm doing a major tune up which includes changing the spark plugs, the park plug wires, the fuel filter, the air filter, the air cleaner mounting gasket, coolant flush, power steering flush, brake fluid flush and hoses, the EGR valve and gasket, cleaning out the throttle body bores, serpentine belt, the cap, the rotor, the oxygen sensors, the pcv valve, the engine oil, the engine oil pan gasket and filter, the tranny oil, the tranny gasket and filter, the tranny auxiliary hoses, the engine oil auxiliary hoses, checking and adjust the timing if necessary.


    Every thing has been done but the spark plugs, the fuel filter, power steering flush, the EGR valve and gasket, cleaning out the throttle body bores, the cap, the rotor, checking and adjust the timing if necessary.

    My question are how do I get to spark plugs 2 and 4. They are located on the upper left side of the engine and are hard to get to because there is some hoese in the way. How do I get around it?

    How do I remove the 2 EGR valve bolts. Do I have to remove the fuel rail to get to them? I consulted the 1991 Eldo/Sev service manual and it doesn't say that I have to remove anything to remove the EGR valve, but I can't remove them with the regular wrench that I have. Do I need some type of special wrench to reach the bolts?

    Do I have to disconnect the battery to replace the cap and rotor? Also, are there special instructions for them?

    How do I clean out the throttle body bores or whatever? Do I remove the throttle body from the engine before cleaning the bores?

    I haven't gotten around to the power steering flush, the fuel filter, and checking and adjusting the timing and I would like to know if there are any special instructions for them as well? For the timing, I just bought a Craftsman inductive timing light from Sears. Is it any good?

    I previously owned a 1996 Concours and boy did the Northstar engine give me hell. I had to spend thousands of dollars on it at the good old dealership just for some of what I did with the 4.9. Boy am I happy to own a 4.9. It is so easy to do stuff yourself as long as you have the right tools.

    Thanks for your help in advance.

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    Joe Sixpack is offline Cadillac Owners Member
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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    What I did on my 93 deville is to put the socket on the plug, and then took advantage of the hex on the end of the spark plug socket to turn it with another socket and/or wrench. It is tight and I scraped up my arm but I managed.

  4. #3
    LacSeville's Avatar
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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    Quote Originally Posted by STSOnly
    My question are how do I get to spark plugs 2 and 4. They are located on the upper left side of the engine and are hard to get to because there is some hoese in the way. How do I get around it?
    put your car up on ramps. they are accessible from the bottom if i remember...

    Quote Originally Posted by STSOnly
    How do I remove the 2 EGR valve bolts. Do I have to remove the fuel rail to get to them? I consulted the 1991 Eldo/Sev service manual and it doesn't say that I have to remove anything to remove the EGR valve, but I can't remove them with the regular wrench that I have. Do I need some type of special wrench to reach the bolts?
    nope, fuel rail stays. take off your air cleaner assy, and it'll be right there. two bolts (use box end/open end wrench) and it easily comes off.


    Quote Originally Posted by STSOnly
    Do I have to disconnect the battery to replace the cap and rotor? Also, are there special instructions for them?


    no special instructions... if you just take the cap and rotor off, the rotor only goes on one way... just make sure when you put the cap on, that it points the same way as when it came off!

    Quote Originally Posted by STSOnly
    How do I clean out the throttle body bores or whatever? Do I remove the throttle body from the engine before cleaning the bores?


    you can... it's not too hard, but you can effecively clean it without. open the butterflies and spray carb cleaner on all that crap you see. get a toothbrush and get that crap out. be sure to get the stuff off the TB bore walls and the butterflies where it makes contact. might as well clean off the bottom of the butterflies while you at it. if you get a buncha carb cleaner down in the intake, no big deal. i had a thin rag with me to wipe as much big stuff out as i could. while the butterflies are open, see those two tubes stickign up at you? take a straightened out coat hanger and rod those out. they don't have to be super clean. they just have to have some decent holes in em! don't worry if the back one is wiggly. it's not a problem, and everybody's does it! it won't come off!

    Quote Originally Posted by STSOnly
    I haven't gotten around to the power steering flush, the fuel filter, and checking and adjusting the timing and I would like to know if there are any special instructions for them as well? For the timing, I just bought a Craftsman inductive timing light from Sears. Is it any good?


    yup, just fine... i guess about everybody prefers inductive! read the post around this one for timing instructions. also, use search and you'll find a lot of the same stuff about setting/checking timing.

    Quote Originally Posted by STSOnly
    I previously owned a 1996 Concours and boy did the Northstar engine give me hell. I had to spend thousands of dollars on it at the good old dealership just for some of what I did with the 4.9. Boy am I happy to own a 4.9. It is so easy to do stuff yourself as long as you have the right tools.


    I feel ya bro... i've never owned a N*, but i like the "simplicity" of the old pushrods!

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    Geno Castellano is offline Cadillac Owners Fanatic
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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    Hold the throttle body bores wide open and look down the bores. You want to clean all the depostis off the walls of the throttle body bores and the backside of the throttle plates themselves. Just use some carb cleaner spray and an old toothbrush. No orifices or anything here to clean or worry about being clogged - just the deposits restricting the air flow at idle and messing up the idle speed control. Just clean the deposits off and forget about it.

    While you have the throttle blades wide open - see those two tubes sticking up at you from the floor of the intake manifold? Those are the EGR delivery tubes and they aren't supposed to be filled with that nasty carbon. Rod it out with a piece of stiff wire until they're clean all the way through. We're just interested in getting the majority of the deposits out so the EGR can flow. There's no need to polish them squeeky clean or anything.

    Forget the EGR valve. It's fine and rarely, if ever, needs service. The EGR tubes under the throttle plates are what need cleaning.

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    Geno Castellano is offline Cadillac Owners Fanatic
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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    You didn't mention two very important things with the cooling system. What about the coolant supplement pellets/sealer that are required with that engine? You need six of the GM coolant supplement pellets or two tubes of the equivalent BarsLeaks "golden seal" powder that's available at Walmart or most any auto store. It's absolutely required with that engine to guard against any internal coolant intrusion.

    Replace the thermostat. With the complete tune up you're doing it would be wise to replace the thermostat with a new OEM replacement. They wear out and after 14 years your original isn't doing the same job it used to. Pop a new one in there with the coolant supplement for insurance.

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    Geno Castellano is offline Cadillac Owners Fanatic
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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    IN order to set the timing just jumper pins A and B of the ALDL connector (under the dash beside the steering column) together to enter the set timing mode - use the timing light to view the timing mark against the tab at the water pump.

    If you want some extra snap from the engine and are going to run premium fuel all the time set the timing up to 13 or 14 instead of the OEM setting of 10. The spark calibration in that package is a little cnservative to allow for marginal fuel octane so if you always use good gas there's some power there with the extra timing.

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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    Thanks Joe, Geno, and Lac for all the help. I put the cap and rotor on with no problems> I cleaned the throttle body bores, plates, and the tubes. I have a problem. My engine idled at 625-700 RPM before the throttle body cleaning. Now it idles at 1500-1700 RPM. I only cleaned the throttle body and I didn't do anything else but put the cap and rotor on. Does anyone know how this may have happened? I would really love to know how so that I may fix the engine idle speed. Thanks.

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    Engine idling unstably from 1500-1700 RPM

    Quote Originally Posted by STSOnly
    Thanks Joe, Geno, and Lac for all the help. I put the cap and rotor on with no problems> I cleaned the throttle body bores, plates, and the tubes. I have a problem. My engine idled at 625-700 RPM before the throttle body cleaning. Now it idles at 1500-1700 RPM. I only cleaned the throttle body and I didn't do anything else but put the cap and rotor on. Does anyone know how this may have happened? I would really love to know how so that I may fix the engine idle speed. Thanks.
    I'm sorry, I failed to mention that I also removed spark plugs 5 and 7, but when I had trouble with simply removing the spark plug wires from 1 and 3, I just reinstalled spark plugs 5 and 7. In order to keep the throttle body bores open, I used a flat head screw as shown in the pics.


    My idle was rough since I bought the car. It was idling unstably from 625-700 RPM and the occasional code that was usually set is:
    E30 'ISC RPM Out Of Range'

    However, the E30 'ISC RPM Out Of Range' code only set when I was doing some 'spirited' stop and go commuting. The code wasn't setting during normal stop and go commuting, but the engine always idled unstably from 625-700.

    Now, after I changed the cap and rotor and cleaned the throttle body bores/plates/tubes (EGR delivery tubes) with 'Gumout' Air Intake & Throttle Body Cleaner that contain acetone and xylene, the engine starts at 3000-3300 RPM and idles roughly from 1500-1700 RPM. I had 3 gallons of gas in the tank, but once I drove the car home, which was about 1.2 miles, my tank is now on 'E.' I am getting the worse gas milege possible. I can't drive the car like this any where. I only drove the car 1.2 miles in the above condition to get home safely and have not driven it since. Also, I got a code that I have never seen, which is E98 'P/N to D/R in ISC range problem.'
    --------------------------------------------------------------------------
    The 1991 Eldorado/Seville says the following for E98:

    Failure Conditions
    1. Engine Running
    2. Gear selector moved from Park or Neutral to Drive or Reverse.
    3. Engine RPM 600 greater than engine speed determined by the PCM
    4. A throttle angle of 20 degrees or less.
    5. Vehicle speed less than 6 MPH

    Action
    1. Retard ignition timing
    2. Code set. No service message

    Description
    This diagnostic test monitors idle speed and gear selection from Park or Neutral to Drive or Reverse when the throttle is in ISC speed range. If idle speed is greater than desired, the PCM will retard the spark and set the code.
    --------------------------------------------------------------------------

    When the code was 'current,' my foot was on the brakes the whole time and I didn't move the car an inch. After the code set, I turned the car off and then turned it back on 5 minutes later. I drove 1.2 miles and the code didn't set again. It is now a 'history' code.


    I'm not sure why the engine is starting at such a high RPM and idling unstably from 1500-1700 RPM.

    Ok. Let's say if you start your car and your foot is on the gas at the same time. That's how the car feels when I start it. When I shift from park to (D), take my foot of the brakes, and not put my foot on the gas, the car takes off and as the speed increases, it shifts to the next gear.

    At idle, the throttle body lever rests against the ISC plunger. The two throttle body blades are slightly open at idle. Could it be that the blades are open too much at idle? I'm not sure but before I cleaned the throttle body, the blades were filled with so much carbon that I couldn't see the bores when the blades were closed. Now, since I cleaned the throttle body, I can see the bores a little because the blades are slightly open at idle, see the pics. Is it supposed the be like this? Thanks for your help in advance.

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    Re: Engine idling unstably from 1500-1700 RPM

    I'm sorry...happy Holiday!

    The above seven pics are described as follows:
    The first two pics show when I used a flat head screw driver to keep the throttle body blades open during cleaning.
    The 3rd pic shows the blades closed.
    The 4th, 5th, 6th, and 7h pic shows the new cap, the old cap, the new rotor, the old rotor.

    I'm not sure whether or not that the old spark plugs are affecting the base unstable engine idling (before and after cleaning the throttle body), but I have provided pics of spark plugs 5 and 7 below. I was unable to remove 1 and 3 so I put 5 and 7 back in. I plan on having a mechanic scrape his knuckles removing all of them, especially 1 and 3 (correction: 2,4,6,8 are easy).

    The spark plugs are AC Delco and the numbers on them are R45LTS6. I'm not sure what kind of AC Delco plugs they are and I don't know how to tell if they are good or bad. Maybe you guys can tell by the pics. They got the black stuff on them as shown in the pics. They will be replaced as soon as I get the idling problem fixed. Thanks in advance.

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    bigred is offline Cadillac Owners Fanatic
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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    Your ISC set point needs to be relearned by your ECM. Fortunately that's real easy. Disconnect your battery. Go get something cool to drink. Have a few sips. Reconnect your battery. Drive.


    Should be OK now. If not, your ISC may be shot. Or your throttle shaft is binding in the body, not allowing it to return to proper idle. The lever should definitely be up against the plunger. Let us know.

    I can't tell well enough from the photos what shape the plugs are in but if you have emissions testing in your area, I would definitely go with new AC Delco R45LTS6 plugs. All the other "recommended" plugs for our engines are a little too hot; they make the cold engine feel a little better but push HC & NOx levels too high.

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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    for more details check your service manual for ISC relearn procedure or something similar. It's very common after cleaning your TB that this happens. Once the bores and plates are clean, there is more gap between the two and more air gets in! "Relearn" the idle where to be (how "open" the plates are at idle) and you'll be fine.

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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    It might be easier to just disconnect the battery instead of relearning the idle. The computer assumes the TB is clean (like it is now) after a memory reset, so that may fix the problem.

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    Geno Castellano is offline Cadillac Owners Fanatic
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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    Right. I forgot to mention disconnecting the battery negative cable for 30 seconds to reset the idle speed learned values for the clean throttle body! That may be part of the idle speed control problem. Also, you may need a new idle speed control motor. Either the idle speed control motor may be failing and/or the closed throttle switch inside the idle speed control motor is failed so the idle speed control cannot tell when the throttle is closed.

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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    Thanks everyone for your help. It's greatly appreciated.

    Before I cleaned the throttle body, I disconnected both cables from the battery and removed it completely from the vehicle. The battery was removed from the car for about 4-5 hours. After I reconnected everything and started the car, that's when I noticed the extremely high idle. I then checked the throttle body lever to see if it was resting against the plunger and it was. Next I did the 'Idle Learn Procedure,' then I turned the car off per instructions. When I turned it back on, engine idle was still the same.

    Under 'Throttle Body Cleaning Procedure,' I noticed that it reads:

    (After 'Throttle Body Cleaning Procedure')
    1. Remove or disconnect negative battery cable to reset learned TPS value
    2. Recheck TPS value with ISC retracted to assure TPS parameter (ED01) is within -1.0 to +1.0 limits.
    3. Perform 'Idle Learn Procedure' described later in this section.

    I didn't perform number 2 as described above. Could this be part of the problem and does anyone know how to perform no. 2 as described above?

    Also, is there anyway that I could check whether or not the ISC motor is operative?

    In the meantime, I'll be reading the service manual extensively and will keep everyone up to date. Thanks again everyone and I hope that you are enjoying your 4th of July.

  16. #15
    Geno Castellano is offline Cadillac Owners Fanatic
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    Re: Hi. I need lots of help concerning the 4.9L. Thanks.

    Search in the archives using "ISC" and "idle speed control motor" and "closed throttle switch" and read the discussions on the subject.

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