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HT4100 4.1, 4.5, 4.9 Discussion, car is dieing at idle. P048 current trouble code. in Cadillac Engine Technical Discussion; alright, engine is cold and i pushed the diaphragm up as far as i could and it did not die ...
  1. #16
    cadillaceldo93 is offline Cadillac Owners Member
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    Re: car is dieing at idle. P048 current trouble code.

    alright, engine is cold and i pushed the diaphragm up as far as i could and it did not die but did drop rms. with engine off i tried to push diaphragm up it is much harder to push up but i pushed it up as far as i could and then plugged the input with my finger and released and the diaphragm released . so now what do i need to do? it wasnt running as bad as it was when i posted last seems like the cold engine runs better. not for sure if this helps but i changed my spark plugs and spark plugs wires before this problem started happening could that have anything to do with this?

  2. #17
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    HUF is offline Cadillac Owners Connoisseur
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    Re: car is dieing at idle. P048 current trouble code.

    Quote Originally Posted by cadillaceldo93 View Post
    alright, engine is cold and i pushed the diaphragm up as far as i could and it did not die but did drop rms. with engine off i tried to push diaphragm up it is much harder to push up but i pushed it up as far as i could and then plugged the input with my finger and released and the diaphragm released . so now what do i need to do? it wasnt running as bad as it was when i posted last seems like the cold engine runs better. not for sure if this helps but i changed my spark plugs and spark plugs wires before this problem started happening could that have anything to do with this?
    Well, if the diaphragm moved when the input was plugged with your finger - the EGR valve is shot.
    If the cold engine did not stall, your EGR passages are not in great shape.

    Rather closed when open EGR valve should cause less drivabilty issues than all time open EGR valve, so you probably can drive like that (fuel economy may drop, emission may be not good either, some spark knock at light throttle when engine is very hot may happen too).

    Sure, you could mess up the plug wires, spark plugs , etc. Make sure (double check) the wires routed correctly to correct cylinders.

  3. #18
    cadillaceldo93 is offline Cadillac Owners Member
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    Re: car is dieing at idle. P048 current trouble code.

    ok so i guess ill buy a new egr valve but getting it on is probably something im not going to be able to do it looks extremely difficult and time consuming and yeah it did drop and it didnt drop slow it just came down i could not get it pushed up all the way with the car off it was very difficult to push the diaphragm up. and why would a bad egr valve cause these problems?

  4. #19
    the recluse is offline Cadillac Owners Connoisseur
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    Re: car is dieing at idle. P048 current trouble code.

    Quote Originally Posted by cadillaceldo93 View Post
    and why would a bad egr valve cause these problems?
    Ok, I'm going to give you the mechanics/mechanical description of how this system works. So here goes:

    The Exhaust Gas Recirculation (EGR) system helps to reduce vehicle emissions by introducing a small amount of exhaust gas into the engine's intake manifold. Re-burning this used fuel reduces combustion chamber temperatures. EGR failures can be subtle and are usually progressive.

    An EGR system starts at the exhaust valve or manifold, where a small channel redirects a certain amount of the spent gases toward the EGR valve. Then it will be opened by the engine computer (like the one in your car, it's opened by the computer controlled solenoid). Once the valve is open, a predetermined amount of exhaust flows into the intake manifold, and from there into the combustion chamber.

    Essentially, there are only two types of failure: the engine receives either too much or too little exhaust gas. Failures are usually due to the EGR valve sticking open or shut, but can also be due to a leak in the system. The EGR valve can stick because it is not receiving the vacuum or electric signal to move, or because it is dirty and encrusted with carbon.

    An inoperative or clogged EGR valve will result in a rough idle, poor fuel economy and possibly a loss of power. Loss of power is especially prevalent with valves that are stuck open, as this will permit hot exhaust gases to constantly enter the combustion chamber when they are not needed. These gases will displace the air and fuel that your engine needs, causing a loss of power.

    So there you have a "Cliff Notes" of the basic EGR system. On your particular engine, there are rods under the butterfly's of the throttle body in the intake manifold. That is where the EGR feeds back the exhaust gases and these usually clog with carbon. It was suggested that you rod these out because in the cases where they are clogged, it renders the EGR system useless; causing the problems mentioned before.

    The easiest way the remove the EGR is to remove the throttle body. If you don't want to go that route, a 13mm crows foot with a 4" to 6" extension and a telescoping magnetic bolt fetcher to set the bolt back into position is another option. Try and clean the passage ways the best you can with some picking, scraping, and carb cleaner before re-assembly.

    HTH, and have fun.

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    cadillaceldo93 is offline Cadillac Owners Member
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    Re: car is dieing at idle. P048 current trouble code.

    ok thanks for all the help i might take a shot at replacing it myself. but for now im off to work!

  6. #21
    cadillaceldo93 is offline Cadillac Owners Member
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    Re: car is dieing at idle. P048 current trouble code.

    i changed my EGR valve and my car is still dieing when i come to a stop or am idling?

  7. #22
    the recluse is offline Cadillac Owners Connoisseur
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    Re: car is dieing at idle. P048 current trouble code.

    Did you ever check for a vacuum leak? You could have a problem with the EGR solenoid, as it is run, in part, by vacuum. Look for a vacuum leak.

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    cadillaceldo93 is offline Cadillac Owners Member
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    Re: car is dieing at idle. P048 current trouble code.

    there is a possibility of a leak. all the hoses coming off the TB hard hard hoses so some broke getting the TB off but if replaced them with vacuum hoses but theirs a chance i dont have a good connection i guess.

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    the recluse is offline Cadillac Owners Connoisseur
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    Re: car is dieing at idle. P048 current trouble code.

    Take some carb cleaner and spray around all the vacuum connections. Spray around the base of the TB. Spray the TB itself (just not down the butterflies). Spray ALL the vacuum lines. IF the engine runs right or idles out fine (it will only be for a moment), you've found the vacuum leak; R&R the line.

    You'll have vacuum lines going all the way up to the firewall (passenger side). These run the vacuum diaphragms under the dash for the A/C controls. On my car I had to replace about 12 feet total of line due to bad cracking and dry-rot. I've also had lines that were cracked that looked in tact. That's what the carb cleaner is for, seals up the crack just long enough.

    Try it and report back.

  10. #25
    cadillaceldo93 is offline Cadillac Owners Member
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    Re: car is dieing at idle. P048 current trouble code.

    ok. i got a couple of questions. 1st how much would it cost to have a shop replace all the rubber vacuum hoses that come off the TB? 2nd what should my cars rpms be idling at? i think when i first changed my egr valve everything was ok then one of the vacuum hoses became disconnected while driving. then i tried fixing it and just didnt do a good job fixing the problem.

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    the recluse is offline Cadillac Owners Connoisseur
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    Re: car is dieing at idle. P048 current trouble code.

    $20 will buy all the vacuum lines in the car and should only take about an hour to do it. A shop could charge you $100+ for literally nothing.

    Find the leak, if it exists, and fix it first. Run a zip tie around the base of the hose to hold it on if you have to.

  12. #27
    brougham is offline Cadillac Owners Master
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    Re: car is dieing at idle. P048 current trouble code.

    Quote Originally Posted by the recluse View Post
    Reach up UNDER the EGR valve. you will feel the diaphragm. Press it then and follow instructions.



    It takes some 50 cycles before the motor throws a code, if you were having problems now, it'll probably pop up later.
    Problem codes come up the second the computer detects a problem. Once the problem isn't detected anymore it takes 50 or whatever number of cycles for the code to disappear or turn to a history code.

  13. #28
    drewsdeville is offline Cadillac Owners Master
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    Re: car is dieing at idle. P048 current trouble code.

    Not necessarily. There are other requirements to meet besides the error itself, like recluse states, though there is no standard like 50 cycles. Depending on the error, there is a time, mileage, or ignition cycle requirement that has to be met with the error existing before it will set the code. This is to prevent a plethora of false postives. Your check engine light would constantly be going on and off if there were no "buffers" like this.

  14. #29
    brougham is offline Cadillac Owners Master
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    Re: car is dieing at idle. P048 current trouble code.

    Quote Originally Posted by drewsdeville View Post
    Not necessarily. There are other requirements to meet besides the error itself, like recluse states, though there is no standard like 50 cycles. Depending on the error, there is a time, mileage, or ignition cycle requirement that has to be met with the error existing before it will set the code. This is to prevent a plethora of false postives. Your check engine light would constantly be going on and off if there were no "buffers" like this.
    That's what history codes are for and why a lot of problems don't make the check engine light come on. My point is that once the computer knows or determined there is a problem it's going to throw a code. It's not going to wait for 50 cycles to do it.

  15. #30
    the recluse is offline Cadillac Owners Connoisseur
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    Re: car is dieing at idle. P048 current trouble code.

    Quote Originally Posted by brougham View Post
    That's what history codes are for and why a lot of problems don't make the check engine light come on. My point is that once the computer knows or determined there is a problem it's going to throw a code. It's not going to wait for 50 cycles to do it.
    The number was just a number to make a point. He was thinking "clear the code, fix the problem". Some things, like ignition, will cycle 30 times to run circuit issues. The other thing you need to consider is that not every problem consistently causes a problem, i.e. your vacuum solenoid controlling the EGR faults (for whatever reason) and throws a code. You clear it. It doesn't throw again for a month. Same issue, different time.

    So, yes, the engine might not wait "50" cycles to throw a particular code, but the PART might not fault EVERY time...

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