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Thread: TPS adjustment

  1. #1
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    TPS adjustment

    Should I be adjusting the TPS on my 1996 V8?

    After some research on here I thought the later, from 95 on, V8's didn't need TPS adjustment as they were 'self learning'.

    I've just been having a read on the RPi website and they give detailed instructions on how to adjust it. There's no mention of not setting some models.

    I haven't put a tester on it yet as I don't have a analogue tester so I thought I wouldn't bother.

    On another note, I adjusted the AFM from 0,93 to 1.30 and it greatly improved the driveability. It stopped popping on the exhaust on over run. I've now bumped it up to 1.4 but haven't driven it yet although idle seems a bit better.

  2. #2
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    Yes, they can and DO need adjusting, the holes aren't slotted like early ones, LR's answer was 'buy a new plenum chamber assembly' if it is out of range

    I prefer to drill or slot the holes out slightly to allow adjustment, 290 to 320mV at rest. Measured between the 2 outer wires of the 3 pin inline plug, ignition 'on'.

    Prior to doing this, check that the throttle plate is clean, and airgap is about .05mm.

    1.4 may be on the too rich side, but you can dial in a bit more advance if you like to aid in smooth idle etc. Won't hurt anything else as these low comp engines could always do with a little more degrees BTDC...

    JC
    The Isuzu 110. Solid and as dependable as a rock, coming soon with auto box😊
    The Range Rover L322 4.4.TTDV8 ....probably won't bother with the remap..😈

  3. #3
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    Thanks Justin,

    Just checked the TPS. Looks like the previous owner has already been there, holes are slotted and it comes up as 300mV.

    Timing is at 9 deg BTDC and AFM is now at 1.35.

    Set the base idle as well which was a touch low, so I'll see how it behaves through the week. So far it feels better than it's ever been. It certainly feels stronger.
    I hope all this improvement isn't merely from the Premium fuel I splashed out on last fill up.

    Ryan

  4. #4
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    Yes, they can and DO need adjusting, the holes aren't slotted like early ones, LR's answer was 'buy a new plenum chamber assembly' if it is out of range

    Justin, I know we have had this discussion before but I still do no agree it is necessary on 14CUX, only on flapper.

    The 14CUX will regard anything up to .545 volts as "idle". this is supported by the Workshop Manual "injection trouble shooting guide" item 18 that idle volts should be 0.085 volts to 0.545 volts and full throttle 4.2 to 4.9 volts.

    I recently tested this by thinking I may be wrong and setting to 0.32. I then noticed because I have a jury rig with the Thor manifold that I was not getting full throttle voltage of 4.2 minimum.
    So I increased the voltage at full throttle as much as possible which just gave me 4.2 and gave .55 at idle.
    It was then obvious that the ECU did not consider this as idle because the injector cut on overrun did not work. I then dropped it to under .545 volts and everything worked normally and still does.

    Interestingly , my seat of the pants feel is that the off idle performance right throught the rev range is now better and logically that should be the case, as the TPS is the leading indicator of air demand. In addition open loop should occur lower in the accelerator depression, and full enrichment be at 4.2 volts.

    I have noticed no difference in idle stability or any other idle issue. It is just no different at idle but better everywhere else.

    Regard sPhilip A
    note i have closed loop, a Thor manifold and Unichip, BUT I do not think it would be any different with open loop.
    Last edited by PhilipA; 7th November 2010 at 07:24 PM. Reason: more info

  5. #5
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    Ah, yes Phillip I remember, and you are probably correct, BUT I have always set these up that way, and the ones I have seen at .2V or .4V etc seem to feel different to the 300mV setting. Could be my imagination, but that is the way I have always done it.

    Probably a throwback to my days of flapper system adjustments, which numbered many

    JC
    The Isuzu 110. Solid and as dependable as a rock, coming soon with auto box😊
    The Range Rover L322 4.4.TTDV8 ....probably won't bother with the remap..😈

  6. #6
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    Quote Originally Posted by PhilipA View Post
    Justin, I know we have had this discussion before but I still do no agree it is necessary on 14CUX, only on flapper.

    The 14CUX will regard anything up to .545 volts as "idle". this is supported by the Workshop Manual "injection trouble shooting guide" item 18 that idle volts should be 0.085 volts to 0.545 volts and full throttle 4.2 to 4.9 volts.

    I recently tested this by thinking I may be wrong and setting to 0.32. I then noticed because I have a jury rig with the Thor manifold that I was not getting full throttle voltage of 4.2 minimum.
    So I increased the voltage at full throttle as much as possible which just gave me 4.2 and gave .55 at idle.
    It was then obvious that the ECU did not consider this as idle because the injector cut on overrun did not work. I then dropped it to under .545 volts and everything worked normally and still does.

    Interestingly , my seat of the pants feel is that the off idle performance right throught the rev range is now better and logically that should be the case, as the TPS is the leading indicator of air demand. In addition open loop should occur lower in the accelerator depression, and full enrichment be at 4.2 volts.

    I have noticed no difference in idle stability or any other idle issue. It is just no different at idle but better everywhere else.

    Regard sPhilip A
    note i have closed loop, a Thor manifold and Unichip, BUT I do not think it would be any different with open loop.


    I can say that adjusting the TPS on our V8 non flapper does affect the idle and general running of the motor, but as you say it should not...then again, it has a mind of its own most days anyhow

  7. #7
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    What are the symtoms of a tired TPS?

    I tried setting the TPS to 0.32 and literally touched nothing else. Then when coming to a stop the rpm would hang at 1200rpm for a second or two and drop down to regular idle speed. Set the TPs to 0.3 and it stops doing this.

    What I have noticed when setting the TPS that it is sometimes difficult to get a consistent reading. If I say set it to 0.3 and then operate the throttle it won't always return to 0.3 but would sometimes jump to some other reading. Surely that can't be right. Fully open always come up as 5.4. I am doing this with the engine warm.

    What I am now finding is that at very light throttle there is a slight hesitation as if I am lifting my foot off the fuel when I am not. With wider throttle openings it doesn't do this and otherwise drives fine. Idling is good as well.

  8. #8
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    Those are the symptoms of a tired TPS, and also a tired multimeter as the max voltage can only be 5 and is usually 4.2 or so. I posted the spec earlier .
    Regards Philip A

  9. #9
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    While the 14CUX TPS is “self adaptive” and not designed for adjustment, adjustment can be a useful temporary fix. I recommend starting the engine and checking the TPS idle voltage at idle. The reason being that the first section of wiper inside the TPS wears the most (as expected being the section which gets the most use) and engine vibration can cause the wiper to produce an intermittent voltage outside the 0.085 and 0.545 volts range. Elongating the holes and bringing a fresh section of wiper into play within the the correct range can fix this pending getting a new one.

  10. #10
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    Quote Originally Posted by justinc View Post
    Yes, they can and DO need adjusting, the holes aren't slotted like early ones, LR's answer was 'buy a new plenum chamber assembly' if it is out of range

    I prefer to drill or slot the holes out slightly to allow adjustment, 290 to 320mV at rest. Measured between the 2 outer wires of the 3 pin inline plug, ignition 'on'.

    Prior to doing this, check that the throttle plate is clean, and airgap is about .05mm.

    1.4 may be on the too rich side, but you can dial in a bit more advance if you like to aid in smooth idle etc. Won't hurt anything else as these low comp engines could always do with a little more degrees BTDC...

    JC
    G’day Justin
    Would you be prepared to give some detailed instructions on how to clean the throttle and adjust the air gap?
    Russ F

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