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Vx Surging Under Load

Discussion in 'VT - VX Holden Commodore (1997 - 2002)' started by FrostyBerry, Nov 2, 2017.

  1. FrostyBerry

    FrostyBerry New Member

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    Hey guys, new member here so be prepared to read :)

    I got my self an automatic vx v6 berlina and as with most vx' it's had it's minor faults but there been one that no one can work out. I noticed it the very first time I drove it, under heavy load it surges (no miss fire or anything) I knew the gearbox was on it's way out so I converted it to manual in hopes that was the problem, running all vt gear (loom and computer) Everything has been married together to get it running and has been running great since except for this problem. Keep in mind it's done it since it was auto but just couldn't notice it as the box was half dead.

    Here's the things I've changed:
    Egr
    Valley Gaskets
    o2 sensors
    Maf
    Leads
    Plugs
    DFI + Coil
    Fuel pump
    Fuel filter
    Crank angle sensor
    Knock sensors
    Bashed out cat (Exhaust shop said blocked cat might be culprit)
    Air filter
    No vac leaks that I can tell

    There's more no doubt but can't think of the rest haha I'll try my best to explain it..
    Say you're driving in 2nd at 40 and punch it, It'll surge through the entire rev range.. Before most people say it's "labouring" If you punch it at 80 in 2nd, same problem. Every damn gear, mostly noticeable over 3k revs.
    If you build up the revs slowly in 1st or 2nd and then boot it it's mostly fine.

    I've taken it to 3 different shops and none of them can access the computer or gearbox? Also, I dunno if this has anything to do with it but the A/C or fan on it's own only blows through the windshield no matter the setting? (climate control vac operated but can' find leaks)

    Aaaaaaaaany help is more then appreciated as this thing is making me wanna commit :D hahha
     
  2. Tonner Matt

    Tonner Matt Well-Known Member

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    Just a couple of other basic things because you hadn't mentioned them:
    Give the Throttle body a good clean, and the Idle Air Control Valve as well.
    The injectors might be due for a service or even require replacing. Maybe try adding some injector cleaner next time you fuel up.

    Try re-setting the Throttle Position Sensor.
    1. Unplug TPS.
    2. Turn ignition on (red lights only) Then turn ignition off.
    3. Plug TPS back in.
    4. Turn ignition to on (red lights only) Then turn ignition off.
    5. Start the car.
     
  3. FrostyBerry

    FrostyBerry New Member

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    Done all of that as well, even tried with the IAC and EGR disconnected. I cleaned the throttle body when I done the valleys around 3 weeks ago. I've also tried to reset the TPS with no luck and even replaced it. There's still more i'm forgetting to mention i'm sure haha i've done just about everything except injectors, most mechanics are saying if it's injectors it'd run like crap all the time though. I've ran nulon injector cleaner and some other expensive stuff holden recommended as well as a couple tanks of 98 with no luck still. It feels as if it loses 10 - 20 hp at it's worst when it's flat out if that helps with more ideas? Cheers
     
  4. Lex

    Lex Well-Known Member

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    Hi
    When you converted to manual did you change the auto memcal to a manual memcal?
     
  5. devilly

    devilly Guest

    a few simple tests you can do that will help narrowing down the search first is, long screwdriver touch to injectors make sure they all have the same tapping going on. second is go into hold mode and up arrow start car and watch the l/h. second is turn to acc and make sure you can hear the iac going through it's steps, you can have a vacuum leak here as well as o'ring is involved. third is as the car warms up you will notice if the tps sensor is kicking in properly as when driving and its 2 on tacho then it will shoot up and drop with the tps kicking in. because its on higher revs and doing it, I'm thinking slow vacuum leak or something blocked. vacuum leak can be from headers, egr, lines and even the top of the block all has rubber seals. through the plenum area. when doing the cover gasket did you clean out injector lines and the rails for the rubber seals. just a thought, hope you solve it.
     
  6. FrostyBerry

    FrostyBerry New Member

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    Thanks for the reply guys, The computer is from a factory manual vt so has the correct memcal as everything works as it should. The TPS seems to be working fine, I have the IAC valve unplugged as it holds revs through gear changes and drives me nuts, disconnecting it and reconnecting it made no difference to this problem so left it unplugged. The EGR was replaced at the very start and that made somewhat of a difference from memory but after a while it came back. When I done the manifold gaskets I left all the lines connected to the rails so never cleaned them. The only thing I haven't replaced is the injectors, I've also had the fuel reg tested and that turned out to be okay. It's got me stumped and same with everyone else I've spoke to about it. I'm on the very edge of getting new injectors but i've blown that much money trying to find this problem i'd probably burn it if I got new ones and still had the same problem hahah

    Also there's a vac line coming off the back of the plenum like all ecotecs but this has a one way valve with just the one hose going to the fire wall? I used to own a vs and noticed they had a T piece type connection just after it came out of the manifold and had 2 hoses running either side of the firewall? Do vt/vx only have one line or is there supposed to be 2? Mine has climate control where the vs didn't so that might just be the difference?

    Really appreciate the ideas fellas :)
     
  7. greenacc

    greenacc Searching for the billion

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    Fix the IAC issue so everything is working 100%.
    Sounds like you still have a fuel supply problem to me, possibly a blockage in a fuel line.
     
  8. devilly

    devilly Guest

    plug the iac back in as it's a stepper motor, surging from my understanding is either a vacuum leak so under throttle body hose. 3 hoses back of plenum zippy lock there. egr gasket silver one no gasket goo, it could be stuck open or closed. for me anything weird on the tacho with revs e.t.c could be the tps.

    or something slightly blocked that when you put your foot down is more noticeable like the filters inside the injectors so maybe try injector cleaner which will also clean the lines and everywhere the fuel goes. do some test they are free and injector cleaner is cheap enough, could even fuel up at a different station sometime this works as well.

    only other thing I can thing of that is computer, timing, fuel related is the o2 sensors. cant halve tell I've had a heap of problems with mine lol :)
     
    Last edited by a moderator: Nov 4, 2017
  9. lout

    lout Well-Known Member

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    when you say mechanic cannot access computer
    do you know what message they get
    and are they bigger shops or small shops
     
  10. greenacc

    greenacc Searching for the billion

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    Probably trying to use OBDII scan tool.
     
  11. FrostyBerry

    FrostyBerry New Member

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    How do I stop it holding revs through gear changes if I plug the IAC back in? It takes a good second to drop revs from say 3k down to 2k when changing up gears. As far as I can tell it just gets rid of the auto choke? Cold starts I have it so it idles around 500rpm, bit temperamental if you try and drive it with out it warming up and once it's warm it idles around 1000 - 1100 which is annoying but i'd much rather that then how it drives with the IAC connected.

    All throttle body hoses and plenum hoses are fit snug and not leaking, same as the vac box thing behind the block. I've run 3 bottles of injector cleaner in it over the last 4 months or so as well as a couple tanks of 98 with no change and tried different servos.

    Mostly just small mechanics, I dunno what they used but it was a hand held snap on tool that plugs under the dash. One shop said he could be in the car when I drive it and get some live data from it but want's around $200 for the possibility of not figuring out the problem.. I live in a pretty small country town so mechanics are pretty limited. One shop I took it to is well known for building high powered commodores (700hp+) and worked with plenty of v6's and everything they suggested I'd already done. I plan on putting an ls1 in it in the next 6 months or so but just wanna get this problem sorted before I do so I can somewhat enjoy the car with the v6 haha

    I've done just about everything to figure out this problem.. There's heaps of stuff I can't remember until some one says to try it that I've already done, the only thing I haven't changed is injectors but every one has said if it's them it'll run like **** all the time?

    Thanks again for the suggestions
     
  12. greenacc

    greenacc Searching for the billion

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    If IAC is not plugged in it won't close the port when needed so it could be causing your air fuel ratio to be out of whack when you floor it and explain the surging You notice.
    Have you tried the idle relearn procedure with the IAC plugged in? It's there for a reason so unplugging it won't help things ( just changes the problem )
     
  13. FrostyBerry

    FrostyBerry New Member

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    Yeah i've tried it, with it plugged in it makes no difference. Same as EGR, I've tried that plugged in and unplugged as well as the IAC plugged in and unplugged with both making no difference no matter how it was done.
     
  14. greenacc

    greenacc Searching for the billion

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    Ok what if you clamp the vacuum hose to the cabin to seal off those leaks in the AC system? Perhaps they are creating a vacuum leak going all the way back to the engine? Which is ******* with fuel mixture making it feel like low fuel pressure ;)?
     
  15. FrostyBerry

    FrostyBerry New Member

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    Tried that as well :(
     
  16. greenacc

    greenacc Searching for the billion

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    And get a new IAC that actually works?
     
  17. FrostyBerry

    FrostyBerry New Member

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    I've tried another IAC off another vx that works perfectly fine.. Still had the same problem so I put my IAC on their car and they didn't and still don't have any problems..
     
  18. greenacc

    greenacc Searching for the billion

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    Ok, have you checked the vacuum bulb tank thingo behind the front bumper? They can crack and leak vacuum. Might explain both your AC issue and the surging issue? Double win :)
     
  19. FrostyBerry

    FrostyBerry New Member

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    Didn't even know of such a thing! I'll check it asap haha thanks
     
  20. greenacc

    greenacc Searching for the billion

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    It stores vacuum so your AC controls still work going up hills and when you fang it lol. On the VS it's in front of the passenger wheel arch.
     

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