2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........
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1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out........... in Past Cadillac Vehicle Discussion; Im hoping someone here can help me. I have a 2004 Deville that I recently took to my local Cadillac ...
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    hearseman's Avatar
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    2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    Im hoping someone here can help me. I have a 2004 Deville that I recently took to my local Cadillac dealer for an oil leak repair. It was the half block which didn't make me happy ($4000.00). After they re-sealed the half block and replaced the valve cover gaskets, I drove about 5 miles, stopped for gas, and when I went to restart it, it was running in full rich mode, puking gas, and with the check engine light on. After towing it back to the dealer, they said it had a bad coolant temp sensor. Ever since the repair, it idles at 1000 RPM out of gear and around 650-700 in gear. There are no codes (I checked it myself with my scanner). They worked on it for about 7 days, exchanging parts and finally came to the conclusion that it was "normal" because it is a limo chassis (hearse). Funny, it never idled that way before. Always idled at 650/500 warm.... Alos, my fuel mileage has dropped about 2 MPG. Short of taking it to another dealer, does anyone have any suggestions? My thought is that it may be a bad or incorrect coolant temp sensor. I don't don't if they tried another one or not. They did try an ECM and ICV. Im at my wits end . Thanks, Cliff

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    Lord only knows what they did, because it doesn't seem that they do. 650 IS the correct idle RPM for the Northstar, regardless of what car it is in. They should know that much. I suspect they have no idea what the problem is and are just trying to pacify you. You might check the FPR for an internal leak and give the TB a good cleaning. Tutorials for both are in the Tech Tips section if you need them.

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    I suspect the guy dropped the engine without unplugging the coolant sensor and pulled the wires out of the connector. They kept saying something about a broken connector. I wonder if he wired it wrong? I guess Ill have to call Cadillac and if they cant help, turn it over to my attorney. It ran like a top when I took it in for the oil leak. Im a former Mercedes tech so, Im not familiar with Cadillacs. Keep the ideas coming!

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    Manic Mechanic is offline Cadillac Owners Fanatic
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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    Hearseman, based on your description of the problems I suspect a stuck open EVAPorative emissions purge valve. Since your a former tech you should be able to check it. It's normally closed, with BAT+ on one wire the PCM grounds the circuit to open it when pulling air through the canister. If it's physically stuck open all the time or the circuit stays closed opening it whenever the key is on that's a problem.

    Vernon

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    ----------

    Thanks Vernon. I'll certainly test it. Do you know where it is located by chance? Im surprised that there are no codes. Is that unusual for an issue like this? I would think even a vaccum leak would set a code. Also, remember that the car had fuel running out of it on to the ground when the coolant sensor malfunctioned. I wonder if the raw fuel got into the evap system and damaged something? Im just grasping here.....

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    I don't know if the ECT sensor was the whole problem, it would cause a no start due to flooding first anyway. I'm assuming (you know what that means) that the fuel was blowing out of the exhaust pipes without specific information. The important point is that this was just after you filled up the fuel tank and not before. This supports my theory because the EVAP system is plumbed into the top of the fuel tank to collect vapors for burning later. But it's not supposed to pull vacuum when the tank is full because it can pull liquid off the top of the tank. Since the EVAP system is designed to move fuel, though in a vapor state, having liquid fuel in in due to a malfunction will usually not cause any permanent or significant damage and once repaired it will "dry" out again. A stuck open EVAP valve will also have a vacuum leak but pull it against a normally sealed fuel tank that also give off fuel vapors the whole time, so codes with it are hit and miss and may only set under certain conditions. On a long trip it probably would set a EVAP flow code. Mileage is reduced because extra fuel in one form or another is constantly being pulled into the intake.

    I forget exactly how it's plumbed but it's located on top of the engine, back drivers side, between the throttle body and valve cover. You'll have to remove the cover. It's a small black canister shaped solenoid with a clipped on hard plastic vacuum line and a two wire connector. The hard line will have the customary green test cap near by. Check that it's sealed when off (unplugged). If air pulls through it constantly, even a little bit, that's a problem.

    Vernon

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    Vernon, could it be actually mounted to the throttle body? There is a black plastic solenoid on the right side of the TB with a 2 wire connector and one large evap hose. If I unhook the hose and block off the outlet on the solenoid, should my idle return to normal, indicating that it is in fact stuck open?

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    Yes.

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    UPDATE: Ok the EVAP valve test and functions OK. I have thoroughly checked for a vacuum leak and there are none. The engine runs smooth, starts easy, but will not idle below 1000 out of gear. 700 in gear. If anyone thinks of something else to check, please let me know. Thanks!

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    Well, for sh#@s and grins, I went ahead and pulled the intake to inspect the TB coupling and found no cracks. I replaced it and the intake gaskets anyway and there is no change. I am stumped!

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    Do you have access to a scan tool that gives comprehensive live data? I'm wondering if the new PCM and it's programming want the idle higher than before. If you can look through the PIDs and look for DESIRED IDLE, it may be where it's at.

    Vernon

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    Hey Vernon, The dealer installed a new PCM just to see if that was the problem and then put my old one back in. I have an older Matco scanner but, I didnt find a "desired idle" speed screen. They told me some cock and bull story about calling Cadillac Tech Support. Supossedly, Cadillac told them to exchange several components as a test. After none of them reduced the idle speed, they decided it was normal for this vehicle.
    Question: Couldn't a coolant temp sensor with the wrong resistance cause and incorrect idle? Maybe the PCM thinks the engine is colder than it is. Do the Cadillac dealer scan tools not have a provision for overriding the base PCM settings to adjust idle? Mercedes has it.

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    If there's an adjustment possible, a Tech II can adjust it.

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    Hmm. OK. I know someone who has a Tech II . I'll get with him on Monday. Thanks

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    Re: 2004 Deville-High Idle Speed, No Codes. Dealer cant figure it out...........

    If the ECT sensor was the culprit you should have an ECT sensor DTC and/or the temp gauge should be way off.

    I assume while you had the plenum duct off for inspection you cleaned the TB? I'd hate to see you go through all this only to have a dirty TB and thus a throttle plate not closing tightly.

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