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Thread: Won't Start

  1. #11
    Join Date
    Apr 2010
    Location
    Shoreline, WA
    Posts
    408

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    I can't see how a bad TPS would make the idle speed hang up. All the throttle and cruise actions are mechanical as opposed to electrical (at least at the throttle body). Does the idle speed not return if the truck isn't driving? If so, rev the engine up and watch the position of the throttle where the cables attach to the throttle body, if it returns to the idle position but the engine is still idling fast then I would suspect the IAC, to verify that this is the problem, pinch off one of the hoses that goes from the intake pipe to the IAC (they make special pliers but a vice grip and a couple of pieces of wood will work in a pinch (pun intended)). If after pinching off the hose. start the engine and rev it up. If it returns to idle immediately, then the problem lies in the IAC system. Have you cleaned the IAC valve? They can get gummed up.
    Gale Breitkreutz
    '03 Disco
    '74 Series III 88 (sold, 4/13)
    '47 CJ2A

  2. #12
    Join Date
    Jun 2012
    Location
    Old Town, Maine
    Posts
    217

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    Hey Gale, from what I understand the TPSs can go bad and cause iratic idles. Upon starting the truck idles fine wether it is in park or in gear...the problem only arrises when I step on the accellerator, it acts as if the throttle is stuck but I confirmed that it is in the fully closed idle position. I like the sounds of your IAC test (and your pun), going to give this a try this afternoon. I'll post the results.

    Oh yeah, forgot to mention that someone on a different forum had mentioned a bad idle sensor? Guess I'm not familiar, could this be a possiblity?

  3. #13
    Join Date
    May 2006
    Posts
    2,020

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    Parrie,

    Have you checked to see if there is a vacuum leak on the inlet manifold? Yes, Rovers Efi's appear to prefer 12.8 to 13.4v for the ECU's.
    Les Parker
    Tech. Support and Parts Specialist
    Rovers North Inc.

  4. #14
    Join Date
    Apr 2010
    Location
    Shoreline, WA
    Posts
    408

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    Quote Originally Posted by parrie View Post
    Hey Gale, from what I understand the TPSs can go bad and cause iratic idles. Upon starting the truck idles fine wether it is in park or in gear...the problem only arrises when I step on the accellerator, it acts as if the throttle is stuck but I confirmed that it is in the fully closed idle position. I like the sounds of your IAC test (and your pun), going to give this a try this afternoon. I'll post the results.

    Oh yeah, forgot to mention that someone on a different forum had mentioned a bad idle sensor? Guess I'm not familiar, could this be a possiblity?
    What the TPS does is sense the throttle position to let the ECU know how much fuel to squirt into the engine from the injectors. the only time I've ever seen a TPS make the idle stick is when it gets stiff and won't allow the throttle plate return to idle. The variation of idle speed to load is controlled by the IAC by bypassing air around the throttle body. Just as a check, take the hose off the throttle body, have somebody operate the accelerator, and verify that the plate is indeed closing completely. This has to be done with the engine not running. This shouldn't be this complicated. the system on this truck is pretty crude compared to the new stuff. (fly by wire throttles, maybe that's why I retired from this business) BTW, I agree with Les about checking for an intake leak, a big enough one could act like the IAC though normally a vacuum leak will cause the idle to be poor, but the IAC may be compensating for that. HMMM, now I'm thinking out loud again.
    Gale Breitkreutz
    '03 Disco
    '74 Series III 88 (sold, 4/13)
    '47 CJ2A

  5. #15
    Join Date
    Jun 2012
    Location
    Old Town, Maine
    Posts
    217

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    Thanks again guys. Last evening I went over everything that I can see and could not find any obvious intake leak. Also confirmed that the plate is closing. I removed the IAC for inspection but not really sure what position valve should be in...the valve itself moves freely however it is not in the closed position (should it be?). I cleaned it up and re-installed but there was no change, starts & idles fine, hit the gas and the rpms rise w/o returning to normal. Gale, I did your air hose squeeze test with the engine stuck on high rpm and sure enough the rpms dropped down to normal idle. If your theory is correct it looks like I need a new IAC wouldn't you say?

    PJ, if your still out there, how are you making out getting your started?

  6. #16
    Join Date
    Apr 2010
    Location
    Shoreline, WA
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    Sounds like your diagnosis is making progress. Before I would change the IAC I would clean it out with some carb cleaner. Take both rubber hoses off and then squirt the cleaner in from both sides. also make sure there are no damaged wires at the electrical connector for the IAC (like mouse chew marks, don't laugh, seen that more times than you would think, apparently rodents like the taste of wire insulation) If none of this works then my next step would be replacing the IAC. When you pinched off the valve and the symptoms disappeared you confirmed the source of the condition.
    Quote Originally Posted by parrie View Post
    Thanks again guys. Last evening I went over everything that I can see and could not find any obvious intake leak. Also confirmed that the plate is closing. I removed the IAC for inspection but not really sure what position valve should be in...the valve itself moves freely however it is not in the closed position (should it be?). I cleaned it up and re-installed but there was no change, starts & idles fine, hit the gas and the rpms rise w/o returning to normal. Gale, I did your air hose squeeze test with the engine stuck on high rpm and sure enough the rpms dropped down to normal idle. If your theory is correct it looks like I need a new IAC wouldn't you say?

    PJ, if your still out there, how are you making out getting your started?
    Gale Breitkreutz
    '03 Disco
    '74 Series III 88 (sold, 4/13)
    '47 CJ2A

  7. #17
    Join Date
    Jun 2012
    Location
    Old Town, Maine
    Posts
    217

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    Thanks Gale. I would never laugh at mouse chew marks, little rascles are the enemy! Did a complete inspection of the IAC and cleaned it up but no go. Before I spend the +/-$200 on a new one I'm gonna see if I can pick-up a $30 used one of ebay. I'll post the results. Thanks again!

  8. #18
    Join Date
    Apr 2010
    Location
    Shoreline, WA
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    I second the idea about used parts. One other thing to test though, try unplugging the IAC and see if the symptoms are still there. Might be something in the ECU (I doubt it but I tend to over test things unless I have a good test part to throw on quickly)
    Gale Breitkreutz
    '03 Disco
    '74 Series III 88 (sold, 4/13)
    '47 CJ2A

  9. #19
    Join Date
    Sep 2012
    Location
    Maryville, TN
    Posts
    10

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    Parrie, It's been a crazy couple of days here. I still havent had time to really dig into my list of issues to check but I've got a light week so we'll see. One thing that's concerning me, in addition to it not starting, is that my heater and a/c don't work and my sunroofs. These have been an issue for a few months now. When I noticed the a/c not working I tried swapping the relays and fuses but still no go. I ran a direct current to the blower motor and it worked fine. As the blower doesn't work on the highest setting it's not the resistor pack, so I don't really know what else to check with that system. As for the sunroofs, I also swapped out relays for that and it didn't work, inspected the switches and they seemed fine, so my next item to check is the under-bonnet fuse box to make sure there isn't any corrosive damage. I'm at a loss for why all these have happened. I'm really hoping it's not a huge electrical system failure. I'm not the most savvy at checking these issues, but my buddy has been helping me tremendously so I'm learning a lot. Any advise is greatly appreciated.

    Could all these issues be related?

  10. #20
    Join Date
    Apr 2010
    Location
    Shoreline, WA
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    Quote Originally Posted by pjwells View Post
    Parrie, It's been a crazy couple of days here. I still havent had time to really dig into my list of issues to check but I've got a light week so we'll see. One thing that's concerning me, in addition to it not starting, is that my heater and a/c don't work and my sunroofs. These have been an issue for a few months now. When I noticed the a/c not working I tried swapping the relays and fuses but still no go. I ran a direct current to the blower motor and it worked fine. As the blower doesn't work on the highest setting it's not the resistor pack, so I don't really know what else to check with that system. As for the sunroofs, I also swapped out relays for that and it didn't work, inspected the switches and they seemed fine, so my next item to check is the under-bonnet fuse box to make sure there isn't any corrosive damage. I'm at a loss for why all these have happened. I'm really hoping it's not a huge electrical system failure. I'm not the most savvy at checking these issues, but my buddy has been helping me tremendously so I'm learning a lot. Any advise is greatly appreciated.

    Could all these issues be related?
    It's possible that you could have a leak in the windshield that's getting into the Body Control Unit, the BCU is located to the right of the glovebox and it's a common problem where water gets in there, corrodes connectors and causes all kinds of problems. If you haven't got a factory shop manual, here's a link to a site with a free download of the RAVE manual (factory shop manual, it's what the dealer techs(like I used to be before retirement) use. http://www.landroverresource.com/
    Gale Breitkreutz
    '03 Disco
    '74 Series III 88 (sold, 4/13)
    '47 CJ2A

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