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Thread: Another rough idle question

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    Another rough idle question

    I'm experience occasional rough idle with my vantasy. I've searched the forum for this problem, but I can't seem to figure it out.

    The van starts fine, idle is fine, and drives well. The problem occurs at the second start up. If I wait for a prolonged period of time with the van off (say a run into a store) then start the van again, the initial idle is low and rough. Most recently the van even stalled. My solution has been to feather the gas for ~10 seconds, then the idle goes back to normal and the van runs well.

    I don't think this is the famous Hot Soak problem. The previous owner did a brilliant job installing an intermittent fan that goes on and off once the engine hits a certain temperature (220F i believe? not sure). This fan comes on once the van is off for intervals of about 1 minute on and five minutes off. I don't hear the fan in the cold winter months, but I figure that's because the engine is cold. My problem occurs even in cold temperatures, and even if the van hasn't been driven very far.

    Any ideas? Bad distributor? Cold start sensor?

    Thanks for any help

    Logan

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    Re: Another rough idle question

    I'm getting a strange check engine code now. When I jump the connector, I get one check engine light flash followed by 6 seconds of no flashes. I thought the normal code was an even flashing of the check engine light (1 second on then off). Could this be a bad ECU?

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    Re: Another rough idle question


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    Re: Another rough idle question

    Fuel injection system serviced with new injectors. When returned to service the idle is strange.
    Cold start is perfect. Starts, races at 1200 RPM and settles down to 900 after a few minutes for the warmup idle up bimetallic air valve warms up.
    In drive idle drops to 700, so far so good. Drive car for 10 miles and when put into park idle is 1500 RPM. Turn engine off. Go into store for some things, then restart and engine can just about idle. Very rough and engine shakes bad. Feather the gas for about 10 to 20 seconds and comes pretty much back to normal.
    I am afraid that if I bring the idle down from 1500 to 750 it will never hold idle in gear nor at cold start ups.

    My thought is to recheck the TPS they just installed. The throttle valve assembly has not been cleaned either. Not sure if they should be done before I start to find this problem.

    All sensors in engine have been replaced already.


    MT

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    Re: Another rough idle question

    Have you jumped the Engine Service Connector and checked for codes? If those look good, check the little rubber hoses that connect to the metal tee on the underside of your Throttle Body Intake Tube.

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    Re: Another rough idle question

    Hey Tim:

    Although I religiously check this I decided to clear the system with a hard boot to get more current data.
    I did that and let it sit with battery disconnected over night. Then ran the van again, same issues of course.
    Then checked the codes and it was one flash every 4.5 seconds. No errors.
    I need to look through all the sensors and make sure these nut balls did not leave something disconnected but that is all I got right now.

    I will report back if I find anything wrong.

    MT

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    Re: Another rough idle question

    Tim:

    I was able to look closer this weekend to see what other surprises I may find. I did find some.
    When he had the intake manifold off I asked him to replace the defective warm up air valve mounted under the manifold. I also asked him if he could relocate it for me so I can get to it at any time. So he extended the hoses and that worked good. However the steel tube that coupled one side of the valve to a top section he eliminated with a bypass hose is all. However when I looked closer there was one hose fitting that was not put back. I cannot tell which fitting this is so I could not find where it went. He may have taken care of this but I am not sure. Picture shows this tube.

    The cold warm up works perfect again as a result but the missing hose may be something.

    I also found where he must have disconnect the wire that went to the High Temperature Line Pressure sensor. This is the one I believe you mentioned once in a thread to just ground and leave it there. It was disconnected but I found the wired to it. So I attached to ground by way of a switch so I can turn it off and on at will. I found that when I did this the engine idle went up and stayed there. According to your input on this it was suppose to time out after a few minutes. This one does not, it stays on all the time. Could this be part of my rough start up after warm?It recovers in about 5 minutes of use but still shakes. It is pretty cool down here in Florida now, so I find it hard to believe it is a heat soak issue. You will notice the red wire I clipped on to these for continuity.
    This mechanic also told me that there were more "air tweaking adjustments" inside the air flow section and that a few hours with that he could get it running close to perfect. Not sure what that is all about

    Everything else seems OK. except for the throttle cam. The kick down on it now has a bit of slack on it when the throttle is closed, it use to be a bit taught before. I also noticed that one of the adjustments, left side, was moved a bit and also you can tell that the stop screw on the cam was messed with. So I am not sure were it all is at this point. I did check the manual and they don't seem to have any instructions how to set that screw. So that leaves me with a questionable mixture adjust/idle calibration also. I also noticed that the transmission kick down has changed. Now it down shifts when I back off on the throttle some times but not all the time.



    Sorry for the length of this just trying to get her back on her game again.

    Thanks
    Attached Images Attached Images   

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    Re: Another rough idle question

    The factory set things up a particular way for a reason. IMO relocating the auxiliary air valve was a mistake. Being mounted in the original location makes it a PITA to access, but it was a clean quality install with permanent steel manifold pipes supplying it. I would think the quality of a relocation job would be marginal at best and be potentially problematic. In addition, when changes like this are made it makes it harder for a technician to figure out what's going on if/when there is a problem...........So why reinvent the wheel? FYI, that nipple on the bigger metal pipe (decommissioned vacuum tube for the relocated auxiliary air valve) is the vacuum source for the power steering pump's "air control valve". I can't see the other end of that big metal tube in your pictures, but I assume the other end of it is now disconnected from the manifold??? If that's the case, then the disconnected nipples shown in your pictures wouldn't matter. He would however have needed to supply vacuum to the PS pump air control valve from another source. To me mods like this are messy and completely unnecessary. If I were your mechanic and you asked me to do that, unless there was a darn good reason for it, I would have refused. Okay, nuff said.

    So, in retrospect, any vacuum line and or fitting associated with the old or new location of the auxiliary air control valve would be suspect. Make sure that all fittings, plugs, caps, and lines associated with that mod are tight and leak free. Also check the throttle body intake air tube for cracks and make sure it's sealed at the bottom where the metal tee goes (Part of the decommissioned auxiliary air valve system).

    Unless the problem only happens after hot restarts, that water temp switch would have nothing to do with it. Assuming that red wire going to the sensor is attached to the original wire (the one that used to go to that switch), I would recommend removing that wire from the switch and attaching it (the wire) to ground. That way the ECU will detect a hot condition at start-up and will activate the "pressure-up" VSV at start-up. Assuming everything else is connected proper and the ECU is functioning correctly, there will not be a high idle associated with this. This merely increases fuel pressure a few PSI for the 1st 2 minutes after start-up. If you are experiencing a fast idle associated with grounding this wire, then I would suspect you have the idle-up VSV reverse wired to the pressure-up VSV. Best thing to do is get a diagram and check/verify all wires and vacuum lines are going to the correct VSV's. Tim

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    Re: Another rough idle question

    Roger that Tim:

    A few points that may have left to some confusion here. The issue with the idle occurred before any of the air valve was modified, so as much as I do understand your concerns about the relocation, I don't believe that is involved except for the missing power steering hose. That can be easily tracked down now that i know what it is, thank you for that.
    The test I made with the idle up pressure switch was done prior him doing any work. He just took my external switch out and terminated the wire without putting it back. So I had to search through all the harnesses to find it.
    Again, even before they mucked with it, when I brought that to ground as you suggested the idle went up by a few hundred RPM and stayed there. I also noticed that this did not effect the idle when the AC was on. Since that VSV compensates for the compressor drag, you almost cannot tell the AC idle up is even active since it is compensating for the drag perfectly.

    Since the pressure up VSV only has one wire that goes to it I don't see how it can be reversed. Or maybe I am not referring to the wrong VSV.

    I will check all lines as you have instructed. I also will try the VSV wire to ground again.


    My biggest concern is that he mucked with the throttle stop screw and maybe even the throttle cable since now I see that the kick down has slack in it when the throttle is closed. Do you know of any procedures to calibrate the stop screw and the throttle cable adjustment?
    Like I said, he mention other fine tuning adjustments in the air flow section. None of that is mentioned in the service manual.

    Thanks again Tim for your input. We will get this and share with the folks. Happy News Years

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    Re: Another rough idle question

    Sorry for the long delay. It was my 1st week back to work after the holidays and I had lots of catching up to do. So, IMO the big problem here is somebody has done a lot of work to your van. It's one thing when care is taken to make sure it's all up to factory standards......it's quite another when somebody (or multiple somebodies) take short cuts and/or don't put things back the way they belong. These are by far the worst troubleshooting jobs.

    Sometimes DIYers and/or wannabe mechanics will jump wires, bypass things, cut things out, relocate or hack things they deem to be "improvements". Some of these guys even open sealed parts and/or tamper with things that should never be tampered with. There's no way to know the complete history on your van, but seeing those pics with evidence of the Auxiliary Air Valve hack and the unprotected injector wires did not leave a good impression. Can changes like this be made without creating the problem you have now?.......Sure, but seeing that makes me wonder what else may have been done. Every change is a variable and variables are a big problem when troubleshooting. When I get jobs like this (where things have obviously been hacked or tampered with) the 1st thing I do is try and put everything back to factory specs. Often time that in itself will solve the issue. If it doesn't, then at least the unnecessary variables have been removed and I can begin troubleshooting normally.

    I'm not saying you need to put it all back to factory, I'm just saying that's what I would do. Good luck. Tim

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    Re: Another rough idle question

    Well I spent a bunch of time looking through the entire engine compartment, tracing all the vacuum tubes, checked all wire harnesses and examined the exhaust system as well.

    No doubt the loud noise was coming from the coupler connecting the exhaust manifold to the pipe. This was causing a ton of noise and exhaust to enter into the cabin.

    The results was that all the vac tubes, wires and connections seem to be in good order. It is hard to trouble shoot with this loud exhaust leak so I went to my muffler guy and he looked at it. He said someone had disconnected what he replaced and now that I have used it the gasket there is blown out. That will be replaced when I get back from Vegas, I have a trade show there next week.
    With that issue corrected it should be a bit easier to trouble shoot.
    I still need to get the throttle cam/cables sorted out. I can see they have been moved. I just cannot find anywhere for any procedures in getting the cable, idle mixer screw, and cam stop screw adjusted.

    The van came from a guy that cared for the van. Everything was original and it ran pretty darn good considering it sat in a barn for 20 years and has 270K on it. But even then the engine had some shakiness to it when started hot. That is why I went to the VSV Pressure up suggestion you made. It still idles up to about 200 rpm's when connected to ground. Again, all this occurred before anyone worked on it.

    I will at least attempt to fix the kick down this weekend.

    Thanks for your response. I know how busy it gets, I am self employed also.
    MT

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    Re: Another rough idle question

    Hey Tim:
    Well I got back from Vegas and jumped into the engine. I did what you suggested and removed all of the vacuum hoses and put everything back the way it was originally. When doing that I found one hose that was like a plastic material from the fuel mixture control to the air intake duck that had a crack in it. Replaced that and gave it a whirl. All the vibration went away and ran much better. Then I put the cold idle up air valve back where it came from just to be sure and it was about the same. So now the entire system is back to stock.
    I also had the exhaust couple repaired. Turns out that when they were doing the work they must have removed this and put it one incorrectly. After torquing the three bolts back on they tightened it up and bent the plate that couples this. The 2 donut gasket that were replace 6 months ago must have move or deformed not taking this into consideration. This caused the plate to not mate well. So now I have a warped plate on one side to about .2". The muffler guy said that new donuts would fix it but only temporarily in that one day it will blow out again. So I have to find the section of the exhaust somewhere and either replace it or refurbish it and replace what is there now. But even though it was bent all the noise is gone. Sounds like a car and not a truck. So my only issue is the idle that tends to miss when down under 1K RPM. Now with the muffler noise gone I should be able to hear much better to determine any more vac leaks. I was told there was a way to use my smoker I used for the Porsche to check the vac lines but I am not sure where I would stick it in nor what I have to plug up to find any more leaks.
    So almost there. A few rattles still bothering me and still AC issues.
    This puppy is lucky to have an owner that give her such TLC

    MT

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    Re: Another rough idle question

    I've never used smoke before to check for an intake leak but in principal I think it's probably a good way to chase one down. I've always used a flammable spray (like ether or carb cleaner)......but that can be dangerous and isn't always conclusive. In a well ventilated area with engine running at idle I've sprayed suspect areas. If there's a leak, the spray will temporarily seal or slow the leak and the liquid that enters the intake will cause the engine to surge (as more "fuel" is now there to burn). If you find an area that if sprayed consistently makes engine surge, then that area is suspect.

    I like the idea of smoke better though as it could give a visual reference and no real potential for flash fire (I've had that happen before and it's a bit scary). I'm glad you're making progress . Good luck! Tim

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    Re: Another rough idle question

    Hey Tim:
    If I used the "Smoking Machine" for the test got any ideas as to where I would port it in? If I use the intake of the mixture control unit I would have to make a huge reducer to get it to fit tight. That is doable but kind of dodgy. I would just make it as air tight as I can and let it roll. I should not see any leaks anywhere, at least that is what I think.
    You have any better idea?
    MT

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    Re: Another rough idle question

    I don't know the size of the smoke machines output, but depending on that, you could put it in through the throttle body intake (big open side where the air intake tube goes). As long as you can adapt to prevent air/smoke leaks, you'd just need to put a stick on the gas pedal to keep the throttle body open while putting it in. There's also the PCV hose/port or the port for the brake booster line. Tim

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    Re: Another rough idle question

    I decided to use the "big Hole approach". Have not done yet but will get on it this weekend.
    I am still resting with one issue that is a royal PITA. Engine idling pretty good, a bit of shake but not too bad. However if I shut it down for a minute and start it back up she just barely holds her own. I have to keep giving her gas and feather it for about 30 seconds in order for her to recover. Is there some thing in the system that causes this? It ain't a heat soak problem, even here in Florida it is down in the 40's

    I will still do the smoke test. But his one is a problem.

    Will keep all posted.

    MT

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    Re: Another rough idle question

    Hey Tim:
    You mentioned I should check the rubber hoses on the tee fitting on the intake tube in #5 in this thread. I must be blind but I cannot find it. Is it in the back where I cannot see?
    MT

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    Re: Another rough idle question

    Yes, it's in a PITA place. The tee is roughly in the middle of the rubber intake tube and attaches at the bottom. It's a metal tee that's held to the intake tube with a spring style hose clamp. There are 2 or 3 rubber hoses that attach to it. The one I was particularly interested in was the big one on the back that originally went to your air valve. When he relocated that air valve he would have needed to do something with that port. Tim

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    Re: Another rough idle question

    Gotcha:
    After you recommended I put it all back I did. I know that hose and it is on and the valve is back under the manifold. At least I know it is all back to normal.
    The idle issue has really become a problem. After I use the van for 10 miles the idle is good, in fact that is how I set the idle after it was really warm. But if I shut it down and come back in 10 minutes or so she just barely idles and shakes real bad. So if I want to go it jerks the van and needs some feathering to keep it going. So if I am parked somewhere it is hard not to ram into someone from the feathering and the jerking from the shakes. It almost goes back to normal 5 or 10 minutes later.
    So the idles overall delta is huge to as low as almost a stall to 1500 RPM depending on how long I run the van. Very strange. I may have to get into the air metering assembly and check that out next. You would think with this level of EFI this would be stable. I know it was when I had mine dealer purchased one back in 86.
    Thanks for the come back. Will keep you updated on this mystery.
    MT

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    Re: Another rough idle question

    Have you done the air valve testing (hose pinching) as per outlined in THIS POST?

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