Code 48 Madness - Idle Air Control Issues - Page 2
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Thread: Code 48 Madness - Idle Air Control Issues

  1. #16
    SOPHOMORE ROVER
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    Re: Code 48 Madness - Idle Air Control Issues

    Sounds like you are steadily getting somewhere.

    I wouldn't run additional advance on these motors, I know it's been advised but don't understand the logic used to decide that (any thorough explanation would help illuminate if anyone has a confirmed view).
    What I get if going over 6degree base setting is that the base idle increases and brings the floor setting too close to the ecu control logic, as you are getting.
    It seems like this you have to run the throttle plate too closed to get ideal tickover (confirmed by your observations of IACV fully closed) down to factory settings.
    If the throttle plate is too closed, then each step of IACV is proportionally greater (of the flow through area) than if it where more open from base idle setting. That could be giving you the error response from ecu as expected step request results in too greater response.

    I'd set the timing at maximum 6 degree (on older more worn cam chain you can see a flutter as it flaps a bit) so set it that you get no more than 6 degrees with a strobe. Then check base idle.

    Difficult starting, that compression psi is not that high if it's generally at 120 average, I would expect more cranking to get it going with that figure. General feeling for me is that you need to be 140 and above to be competent at most things.
    It's certainly not a disaster (plenty of engines run for years at that level) but needs to be taken into account for your assessment regarding starting.

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  3. #17
    FRESHMAN ROVER Razorbeam's Avatar
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    I pulled the vacuum line from the fuel pressure regulator. It isn’t cracked all the way through, but it looks a little stretched out and is starting to rot. I’m gonna pick up a new vacuum line and see if that improves the starting.

    I’m still not convinced that the throttle butterfly has anything to do with the idle screw. The screw opens a separate port in the throttle body and doesn’t affect the butterfly valve itself. I’ve included a picture of the throttle body with a circle around the port I’m talking about.
    Attached Thumbnails Attached Thumbnails Code 48 Madness - Idle Air Control Issues-5ec563d4-8770-4c6f-88b6-8c0d4f9902d9_1561605993080.jpg   Code 48 Madness - Idle Air Control Issues-be0effad-8be6-4219-8dbd-6e946a6ea794_1561606019208.jpg   Code 48 Madness - Idle Air Control Issues-0f1963f8-4c67-4709-8f9c-f0d70ff3b29f_1561606396995.jpg  
    1992 Range Rover Country SWB

  4. #18
    FRESHMAN ROVER Razorbeam's Avatar
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    Re: Code 48 Madness - Idle Air Control Issues

    Update: I put a new hose on the fuel regulator with no change to the starting. I did the base idle setting again and I think I got it right this time. The check engine light hasn't come back with a good amount of hot city driving.

    It still starts like crap. It takes 5-10 seconds of cranking then comes to life one cylinder at at time. If I blip the throttle it comes right back down to a nice smooth idle. I feel like it could be a leaking injector, but the plugs are dry when I check them. Starting with ether yields similar results. It starts a little easier, but still pretty rough.
    1992 Range Rover Country SWB

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  6. #19
    FRESHMAN ROVER Razorbeam's Avatar
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    Re: Code 48 Madness - Idle Air Control Issues

    Quote Originally Posted by Razorbeam View Post
    Update: I put a new hose on the fuel regulator with no change to the starting. I did the base idle setting again and I think I got it right this time. The check engine light hasn't come back with a good amount of hot city driving.

    It still starts like crap. It takes 5-10 seconds of cranking then comes to life one cylinder at at time. If I blip the throttle it comes right back down to a nice smooth idle. I feel like it could be a leaking injector, but the plugs are dry when I check them. Starting with ether yields similar results. It starts a little easier, but still pretty rough.
    Another item to consider that crossed my mind. Last weekend I took the truck up to Michigan. Normally when I fill up with fuel I stop the pump before the auto-shutoff. Well, I was distracted washing the windshield and the pump hit the auto shutoff. I noticed a good amount of fuel spilling out from under the truck. Clearly there's a leak somewhere around the top of the tank.

    Obviously, this should be fixed no matter what, but could this leak be causing a lack of fuel pressure when starting?
    1992 Range Rover Country SWB

  7. #20
    SOPHOMORE ROVER Mikieman's Avatar
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    When you filled up and it leaked
    It had to be the overflow hose
    They deteriorate
    It doesn’t effect
    Fuel pressure

    Mine does that
    But my rover runs great
    im an american i dont speak english

    91 classic..it is now parts

    92 lse... not a bucket of rust

  8. #21
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    Re: Code 48 Madness - Idle Air Control Issues

    As above, the tank itself will never be pressurised as it has to work with changes in volume as fuel is used. Many vehicles vent from the fill tube just down from cap, so if you keep pumping in there, it'll ultimately go out through the breather in most cases.

    Fuel pressure, pump is suspended from top plate of tank and sits on a stem reaching down to tank base with pickup resting on bottom of tank (else you'd not be able to use all the fuel). From here it just pressurises the outflow line, via the fuel filter and then straight to the fuel feed rail going round the injector circuit.
    Pressure is held up to required level by the regulator above which pressure it bleeds off in return line back to tank.

    Fairly simple really but tank is always open to atmosphere.

  9. #22
    SOPHOMORE ROVER Mikieman's Avatar
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    On my rovers gas cap
    If I tighten it
    I get vapor lock
    .., after a while...
    it stops
    Then it won’t crank
    So I loosen the cap
    And it fires right up
    Now I just leave it loose
    im an american i dont speak english

    91 classic..it is now parts

    92 lse... not a bucket of rust

  10. #23
    FRESHMAN ROVER Razorbeam's Avatar
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    Re: Code 48 Madness - Idle Air Control Issues

    I'm really starting to suspect my fuel pressure regulator is bad. This morning I went to start the truck and did the thing where I cycle the ignition on and off 4-5 times before I crank it.
    It fired on the first crank, but stalled immediately.
    Second try was a little more cranking, and then fired on a few cylinders then stalled.
    Third try it cranked for a while, then slowly fired up with some help from me on the throttle.

    I can't find any definitive information on the interweb about the Rover V8 fuel pressure regulator, but a lot of general articles make me think I could be sniffing up the right tree.

    The way I understand it is that the vacuum from the manifold decreases the fuel pressure, and as vacuum decreases (and engine speed increases) the fuel pressure increases as well. If mine is faulty it could be giving too much pressure at idle/startup, but higher in the rev range it's less of an issue because the engine requires higher fuel pressure anyway.
    I have tried running the engine with the vacuum line (to the FPR) removed and it has a noticeable detrimental effect on the way the engine idles and revs, so I know the vacuum diaphragm is doing something.

    I really don't want to disassemble the plenum AGAIN, but I'm getting pretty good at it by now and a new FPR can be had for ~$60 so I'm thinking it could be worth the effort.
    1992 Range Rover Country SWB

  11. #24
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    Re: Code 48 Madness - Idle Air Control Issues

    this gives you more in depth info than rave http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm
    2k p38 4.6
    95 lwb 4.6
    01 d2 4.0

  12. #25
    FRESHMAN ROVER Razorbeam's Avatar
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    Re: Code 48 Madness - Idle Air Control Issues

    After some more head scratching and talking to my dad, I don't think it is the fuel pressure regulator at all. I believe that since I get better (not great, but better) starting when I cycle the key on and off 4-5 times before cranking, my fuel system isn't holding pressure. Pressure is held in the system via a check valve which is internal in the pump.
    I believe mine is allowing the fuel to leak back into the tank, thus when I go to crank I am not getting the fuel pressure I need to start and idle right away. When I blip the throttle, more fuel pressure is being added by the FPR which allows everything to run happily.
    To test this theory I bought a 5/16" fuel check valve. I am going to try to install it either right behind the fuel filter or directly out of the pump itself. This should allow the system to prime and then hold pressure in the lines.
    I'm planning on getting this installed tonight and will report if I had any success.
    Question, on the fuel pump can anyone tell me which pipe is the output and which is the return? I believe the pipe closer to the outside of the housing is the feed, but I don't know for sure.
    1992 Range Rover Country SWB

  13. #26
    FRESHMAN ROVER Razorbeam's Avatar
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    Re: Code 48 Madness - Idle Air Control Issues

    On second thought, I decided to go ahead and order a new fuel pump after pulling off my access panel to reveal this mess.
    Code 48 Madness - Idle Air Control Issues-fuel-pump.jpg

    I had always known that it didn't look great, but I never realized how poor the wiring situation was. I got an Allmakes kit for about $110 shipped and it includes the sealing ring and wiring harness.

    I was going to try to salvage this one, but the ground connector broke apart when I looked at it and everything else just looked past it. All the rust on the top was not confidence inspiring. Hopefully this helps my starting issues, or at least improves them.
    1992 Range Rover Country SWB

  14. #27
    SOPHOMORE ROVER
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    Re: Code 48 Madness - Idle Air Control Issues

    That may be more typical of condition than many realise.

    Our current one came to us in similar state, with previous owner hacking into insulation to try and effect a repair. I stripped it out, remade by soldering the wires to pump connects, then recast insulation in epoxy resin to make it competent. Probably started slightly better than your situation though, so more chance of salvaging original.

    That plastic retainer ring will hold any water there during use as there appears no way to drain out easily, I've covered the top of assembly with marine grease to try and prevent so easy a deterioration in future.

    Guess we'll soon see if the pump is affecting your starting, but good to eliminate it though as ours had random non-pumping incidents that left it stranded a couple of times until fixed.

    We await your verdict.

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