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HT4100 4.1, 4.5, 4.9 Discussion, Engine Idle and "almost" stalling problems in Cadillac Engine Technical Discussion; When you remove the EGR valve on a 4.9 there are no tubes or anything below it...just two ports or ...
  1. #31
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    Re: Engine Idle and "almost" stalling problems

    When you remove the EGR valve on a 4.9 there are no tubes or anything below it...just two ports or holes in the intake manifold. They are the EGR ports in the intake manifold, I guess. The EGR valve and that area on a 4.9 rarely if ever needs any service.

    The EGR tubes are the two tubes sticking up below the throttle blades from the bottom of the intake manifold...you look directly down into them as you look down the throttle bores with the throttle blades held wide open...as has been described in at least 100 previous posts...LOL LOL

    Cleaning the throttle body blades and bores is a maintenance item that affects the idle speed control and throttle feel off idle. Lots of times throttle bodies are cleaned and people haven't the faintest idea to clean out the EGR tubes also. THAT is why they are typically desribed and treated as two distinctly different things...because they require two distinctly different cleaning methods, doing one does not guarantee the other and they affect two completely different systems.

    EGR valve cleaned, as often described on this forum, is done/required on the NORTHSTAR engine...not the 4.9.

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    Re: Engine Idle and "almost" stalling problems

    Quote Originally Posted by rmonyer
    Well I spoke too soon. The problem is back. Rough idling off and on at stops, lack of acceleration when stepping on the gas. What should I attack next? Bbob? Kev? Anyone? I am going to check the EGR tubes tomorrow to see if they are clogged again. I'd like to know if they got clogged again in 2 days. If not what's next?

    Time to get a fuel pressure gauge and check the fuel pressure when driving and when the problem occurs. It sounds like the fuel pump may be starting to loose capacity and loose fuel pressure when demand hits it....

    Sounds like the EGR tubes were plugged so they needed cleaning anyway and the throttle body needed it, too, so that wasn't a waste of time eliminating those items.

    The rest will just take some more diagnosis.

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    rmonyer is offline Cadillac Owners Member
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    Re: Engine Idle and "almost" stalling problems

    This morning I checked my EGR tubes again and they are still clean from my cleaning job a couple of days ago. What I did notice was that there is a hose on the back of the air duct that was hanging loose. I probably pulled it loose when I removed the air duct to clean the tubes the other night. What I want to know is what is that tube for? Also, could this hose on the back of the air duct cause my specific problem if it was left disconnected? I re-connected it, and my wife reports no symptoms or problems with the car during her drive to work. I will monitor to see if the problem re-surfaces.

  4. #34
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    Re: Engine Idle and "almost" stalling problems

    Quote Originally Posted by bbob
    When you remove the EGR valve on a 4.9 there are no tubes or anything below it...just two ports or holes in the intake manifold. They are the EGR ports in the intake manifold, I guess. The EGR valve and that area on a 4.9 rarely if ever needs any service.

    The EGR tubes are the two tubes sticking up below the throttle blades from the bottom of the intake manifold...you look directly down into them as you look down the throttle bores with the throttle blades held wide open...as has been described in at least 100 previous posts...LOL LOL

    Cleaning the throttle body blades and bores is a maintenance item that affects the idle speed control and throttle feel off idle. Lots of times throttle bodies are cleaned and people haven't the faintest idea to clean out the EGR tubes also. THAT is why they are typically desribed and treated as two distinctly different things...because they require two distinctly different cleaning methods, doing one does not guarantee the other and they affect two completely different systems.

    EGR valve cleaned, as often described on this forum, is done/required on the NORTHSTAR engine...not the 4.9.
    Thanx bbob
    Guess that it never quite set in that it was 2 different things. Just go in and clean it all.
    I believe that someone told me that the egr tubes were under the valve. Think that was quite a while back in the old forum. So in those hundreds of posts on the subject I must have dismissed the fact that opening the blades was to clean the egr tubes. Had it set in my mind that was a part of cleaning the throttle body. No harm done I guess. Always did the job right.
    Except for the pain in the ass time I had to remove the egr valve to clean what I had been told were the tubes. LOL.
    And I must say...they WERE spotless.
    So much for bad info and assumptions.
    Thanx again bbob
    Quote Originally Posted by rmonyer
    ......could this hose on the back of the air duct cause my specific problem if it was left disconnected?
    I believe that it could. Left mine disconected one time and could barely start the car let alone get out of the driveway. Give it a test. Pull it off and see how it starts. Or even pull it off once its running. See if you get the same symptoms.

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    4.9L FWD idle problems 1991 Sedan DeVille

    I need advise myself,

    My car idled very smoothly more than a few months ago. slowly by slow it started to idle rough. when I first noticed it in Nov 2004 I changed the ISC, had the EGR Cleaned at the dealer {wouldnt pass emissions}, Replaced my plugs, distributor cap, rotor and coil pack in the distributor. after that didnt work it continued to get worse. I replaced my fuel filter, got some carb cleaner from Valvoline cleaned out my throttle body, changed the air filter and PCV. still continued to grow worse. Now Im at a light feeling the engine shake watching my hand vibrate on the wheel and have the slightest clue of what I can do next. Im not showing any codes.

    Are there any suggestions. Its not cutting off or stalling. just idles rough. It didnt idle rough in June when I got it, It happened slowly all the way up until now. I even a few days ago cleaned my heater core and changed the fluid. no help.

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    Re: Engine Idle and "almost" stalling problems

    Well Mr. Smith, I feel your pain. It sounds like both of our cars are doing the exact thing. Shaking at stop signs etc. I have been battling the problem for over a couple of months now. New EGR valve, fuel filter, run rite treatment, EGR tubes cleaned. I just cleaned the throttle body again today with Carb Cleaner as recommended by bbob. The 1st time I went into the throttle and cleaned the EGR tubes, I cleaned the throttle area with WD-40, a hangar, a toothbrush, and a rag. After today's carb cleaner job, I took the car a test drive. So far so good. Accelerates great, and I even "chirped" my front 2 tires when pulling off from a stop. When I floor it, the car down shifts and accelerates smooth. I liked it. After the speed runs, I slowed down to a nice NORMAL idle with no "shaking." We'll see how it act later tonight, and tomorrow. I'll update this forum. Thanks for your post, because I was about to get into replacing plugs, wires, and cap. I will hold off for now.

  7. #37
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    Re: Engine Idle and "almost" stalling problems

    I wonder if O2s synsors have anything to do with it. Im not gettig any codes but I wonder.

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    Re: Engine Idle and "almost" stalling problems

    It continues. After last nights 1st test drive, the results were good. Later that night the results were terrible. The car actually had a hard time starting and stalled on me at a couple of stops. It also was back to the "hiccups" and "hesitation" when I applied pressure to the gas pedal. I was low on gas (3 gal showing on readout), so I put gas in the tank. The car drove better after I got it started, which took 5 to 10 cranks. This morning it started on the 2nd try, but still shakes at stops, and when parked at idle.

    Mr. Smith, I would think that if the O2 sensors were bad, you would get codes reflecting that. I really need a good Cadillac mechanic to give me some advice. I don't mind spending a few bucks on the repair, I just want the correct repair performed. I am trying to stay away from Cadillac's $90 per hour labor fees.

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    Re: Engine Idle and "almost" stalling problems

    Quote Originally Posted by rmonyer
    It continues. After last nights 1st test drive, the results were good. Later that night the results were terrible. The car actually had a hard time starting and stalled on me at a couple of stops. It also was back to the "hiccups" and "hesitation" when I applied pressure to the gas pedal. I was low on gas (3 gal showing on readout), so I put gas in the tank. The car drove better after I got it started, which took 5 to 10 cranks. This morning it started on the 2nd try, but still shakes at stops, and when parked at idle.

    Mr. Smith, I would think that if the O2 sensors were bad, you would get codes reflecting that. I really need a good Cadillac mechanic to give me some advice. I don't mind spending a few bucks on the repair, I just want the correct repair performed. I am trying to stay away from Cadillac's $90 per hour labor fees.

    No...you need to cobble up a fuel pressure gauge and check the fuel pressure. That is a pretty basic, simple test of health for a port fuel injection system. Find an old R12 refrigerant recharge kit/adapter hose at an auto parts store. The fitting for the R12 refrigerant fitting is the same as the fitting on the fuel rail for a fuel pressure gauge. Find an old 50 PSI gauge of some sort and with $2 worth of hose and brass fittings you can make a fuel pressure gauge. Screw it onto the fitting on the rail, tape it to the hood or windshield where you can see it while driving and take a ride. Watch the fuel pressure to see if it drops off or stutters when the driveability issues exist. Simple and basic check. If the fuel pressure is not up to snuff then the fuel pump is the likely culprit.

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    Re: Engine Idle and "almost" stalling problems

    Thanks for the advice again, Bbob. Friday I took my car back to the shop that I had do the EGR replacement and they diagnosed the car with me standing there. I watched them test the fuel pressure. It had 35psi when you turned the key, and it seem to maintain around the same when running. The mechanic looked up the spec and said that the fuel pressure for the car should be at 40psi. Is this true? He didn't think that the 5psi difference would cause the symptoms but wasn't sure. They also pulled a hose (vacuum I think) off of the fuel regulator. With the hose disconnected, the car seemed to idle perfectly. When they put it back on, the car stumbled, and searched for idle. They are going to replace the fuel pump on Monday. I'll update when we get the car back. A side note, they also said that my fuel filter looked really bad when they replaced it about a month ago. One guy said it was really clogged and that could have overworked the fuel pump and damaged it. Since I have no experience.....who knows? I know a clogged artery will over work your heart, so I am thinking the same is true with a fuel pump.

  11. #41
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    Re: Engine Idle and "almost" stalling problems

    I started mine when it was cold and it ran fine. I went into diagnostics and waited for the auto light to come on. When the auto light came on, indicated the computer is going in closed loop, it ran bad. I had a bad ground to the O2 Sensor. It helped dramatically. But some of the problem is still there. Share what happens with yours.

    Blaze

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    Re: Engine Idle and "almost" stalling problems

    Quote Originally Posted by rmonyer
    Thanks for the advice again, Bbob. Friday I took my car back to the shop that I had do the EGR replacement and they diagnosed the car with me standing there. I watched them test the fuel pressure. It had 35psi when you turned the key, and it seem to maintain around the same when running. The mechanic looked up the spec and said that the fuel pressure for the car should be at 40psi. Is this true? He didn't think that the 5psi difference would cause the symptoms but wasn't sure. They also pulled a hose (vacuum I think) off of the fuel regulator. With the hose disconnected, the car seemed to idle perfectly. When they put it back on, the car stumbled, and searched for idle. They are going to replace the fuel pump on Monday. I'll update when we get the car back. A side note, they also said that my fuel filter looked really bad when they replaced it about a month ago. One guy said it was really clogged and that could have overworked the fuel pump and damaged it. Since I have no experience.....who knows? I know a clogged artery will over work your heart, so I am thinking the same is true with a fuel pump.
    Like Bbob alluded to, fuel pressure just sitting is different from actual pressure when driving around in the vehicle. I changed the pump on my 89 deville and noticed that it had the GM filter sock that can collapse and partially clog up the works.

    What I don't remember off hand, is whether it had the notorious fuel baffles in the tank (ala 90's chevy trucks) that can seperate from the tank and bend your pump mounting tube so that flow is reduced. I also would advise that you put in a new isolator to avoid having to do so in a few months (right after you fill it up of course). Also make sure that your mechanic pays special attention to the wiring harness in tank so that you aren't dropping the tank again due to corrosion at the terminals causing you problems.

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    Re: Engine Idle and "almost" stalling problems

    More on my 1993 Deville: I got the car back tonight with a new fuel pump. My tech wasn't sure it was the fix and asked me to drive it tonight and tomorrow to check it out and let him know how it went (I haven't paid for the work yet). I did. It still sucks. It's not stalling now, but it still idles rough, and hesitates on acceleration off and on. Not as bad as last Friday, but it's still there. I pulled the codes from computer using the OFF and WARMER button. I have codes: E22, E23, E31, E52, and E70. 2 of these codes refer to the TPS sensor, one refers to the MAP sensor. Any suggestions on where I should go from here. I am dropping the car off again to the repair shop.

  14. #44
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    Re: Engine Idle and "almost" stalling problems

    I think there is something unhooked. Check all the connectors by the back of the engine and by the distributor.

    Blaze

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    Thumbs up Re: Engine Idle and "almost" stalling problems

    Well I "Bit the bullet," I took my car to Cadillac. The visit turned out good. They replaced my altenator 1st (it tested bad), and wouldn't you know it......the freakin' car runs normal now? I was told that the altenator was making a "whining" noise (which I knew about) and that the noise was setting off the "knock" sensor that happens to be located near the altenator. This "knock" sensor information was making the computer change the air/fuel mix or something of that sort, which was the reason for my idle and acceleration problems. Wow. All of these weeks, and uneccesary work at a "local joe schmoe" repair shop, to find out if I had replaced the bad altenator (that I knew about) 1st, I would've solved the problem . I say I knew about the altenator because it had a "whining" sound when the engine was idling, and when you accelerated it made a louder, higher pitched sound. Months ago, a mechanic told me that it probably had bad bearings in it. Anyway, the new altenator fixed the problem for a total of $337 installed. I can't complain, I deserved it :banghead2 . I am going to take this car to Cadillac now for anything above oil, filter, tire changes and save myself the hassle. This local Caddy store is Ayres Cadillac in Burlington, NJ. http://www.ayrespontiaccadillac.com/ They are a Christian owned and operated business, and it showed! Friendly service, with a nice, quiet, peaceful service area and showroom. No loud music, no cigarette smoke, no yelling and screaming going on in the service bays. My wife and I were impressed to say the least. I was told that I should get a tune up for another $350-400, and when I priced other shops (Firestone's etc) it was the same cost. So I don't save a buck using the "knock off" shops, plus I get AC Delco parts at the Caddy Dealer. WIN WIN. I am just glad it's all over. I plan to get the tune up in a couple of weeks. I hope this post helps someone else. Thanks to all that commented and tried helping me out. The EGR clean was a definite need and it helped me learn something about my car. Same with the fuel pressure check etc. Thanks again Bbob, kev, and others.

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