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VT Dual Fuel slowly loses power on petrol when warmed up

Discussion in 'VT - VX Holden Commodore (1997 - 2002)' started by lignum1966, Apr 19, 2015.

  1. lignum1966

    lignum1966 New Member

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    Hi there , first up my Vt is Ecotech V6 , dual fuel , pretty stock , just Big CAI and Hi flow filter , Supercat Catback exhaust and Mace Enginering ECU chip .
    (and of course dual fuel) . Christmas before last I put a fuel injector rebuild kit through it . (filter pots , o-rings and pindle caps)
    Car was running so bad on petrol recently it would basically start and idle but stall out as soon as I went to rev it a little . Had been getting worse on and off for a while so
    last weekend I removed the fuel tank , cleaned it out , replaced the complete pump unit that was very disgusting , dirty , blocked and rusty looking . Replaced fuel filter and fuelled the car up (I used Caltex 98) (Thats almost gone now so I'm gonna try something different but in this case I don't see it being that fuel) . Started pretty well straight away on petrol , revved freely and drove nice in a quick test . However all wasn't as good on the way to work next day after the car had warmed up !

    So the car still runs fine on Gas , hot or cold . On petrol it starts anytime and runs fine when cold , but as it gets up to running temp starts to feel a loss of power and slightly rougher running (missing or surging) at or around around 1500 rpm approx which is 60kph in 3rd approx (and the same in top around 80ish) , and then generally starts to run worse and lose more and more power till undriveable or close to it . However I flick it back on gas and it runs just fine again . Now the Mace chip is a recent addition but the fuel problem seems to be there with that chip or the original ecu chip in use .

    I don't know much about fuel regulators , cant find any obviously damaged or leaking vacuum lines , and (maybe stupidly) have sort of discounted electrical problems as the car always seems to be fine if I run on gas .

    Hours of reading either here or on google and mostly getting sidetracked with other posts have made me no wiser (as to this problem at least) ... so I'm hoping someone here can !

    Bazz
     
  2. dirty hands

    dirty hands Active Member

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    just saw you have an EGR question as well -- if faulty code 18 or 29

    if no better

    low fuel line pressure when hot

    you have done the tank /fuel pump and filter
    injector 0 rings not leaking
    no smell of petrol
    cant see it being injectors them selves if ok on gas
    not a coil pack or DFI problem gas runs perfect

    have you cleaned the thottle body and or cleaned /checked the MAF

    correct - fuel pressure regulator is vacume operated - no code will exist

    if no vacume leak there --- did you know a faulty fuel regulator can sometimes fill up with petrol

    think about checking then replacing the fuel pressure regulator - shares both injector lines ---wait and see if it improves
     
    Last edited: Apr 19, 2015
  3. EYY

    EYY Well-Known Member

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    Has it ever backfired on gas?
     
  4. lignum1966

    lignum1966 New Member

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    Thanks for the replies , I cleaned the maf and in fact swapped it out with a couple of spares I have to try as well (no guarantees on the spares though) , haven't yet cleaned throttle body since I did the injectors .
    Never backfired on gas or petrol .
    I have an ALDL cable so I'll have to hook the lappy up and see if I can find any other related errors with the provided software . I've never had the check engine light come on using petrol , does occasionally come on for a little while using gas but then again it has done since I had the gas system fitted 3 yrs ago . Had both o2 sensors replaced at that stage although I suspect they were fine and the gas fitter just didn't quite get something perfect when installing but has always run well enough on gas to keep me happy as I use petrol 75% of the time anyway .

    I only replied in the other thread as this one didn't seem to post when I tried - maybe just a delay for moderators to check it first as I'm new to posting here , anyway I thought that problem might be something similar .

    Oh , is there a way of testing the regulator or pressure ?
     
    Last edited: Apr 19, 2015
  5. lignum1966

    lignum1966 New Member

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    After hooking up my car to my laptop it has apparently recovered the following error codes

    Set DTC 45 - rich exhaust
    Set DTC 57 - injector monitor line failure
    Set DTC 65 - left side 02 rich
    Set DTC 76 - c/l integrator failure
    Set DTC 92 - low fan communication error

    The software is TunerPro RT .
     
  6. GMDriver

    GMDriver New Member

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    DTC 92, usually sets when the laptop is hooked up to the OBD plug & you have engine running, just clear the fault with the ignition on (engine not running)when your done.
    If it still logs without the engine running check your fan relays/fuses
    DTC 57, that will set when your running LPG as the volts to the injectors is cut off.

    The other DTC 45,65 should all be related to the LHS 02 sensor, check it hasn't come unplugged, if not replace both sides
    DTC 76 sets when 1 bank (side) is running way richer/leaner than the other
     
  7. dirty hands

    dirty hands Active Member

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    injector fuel line pressure needs a gauge ..bit more complicated

    any vacume device
    old school way
    a piece of vaccume hose on the regulator --suck in the air

    block off the hose with your tongue---- if it holds pressure ..should be ok
     
  8. Nut Kracker

    Nut Kracker Donating Member

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    You're say as it gets hotter the engine gets worse.......
    I'm wondering if the CTS (coolant temperature sensor) is faulty,
    therefore giving the PCM incorrect information, regarding the proper fuel delivery to
    the engine, as it gets hotter.
    This 'could set the rich exhaust codes etc.

    When the engine is cold, the CTS tells the PCM to delivery more fuel (quicker injector pulse rate).
    Sort of like an electronic choke.
    As the engine's temperature rises, the value of the CTS changes, relates that to the PCM and the fuel decreases.
    Just like pushing the choke in.
     
  9. lignum1966

    lignum1966 New Member

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    I'm with ya thinking about the 02 sensor as that apparently sets of the check engine light , however it only sets it off when running on gas . I'll have to try to clear the codes again (couldn't clear them for some reason or other last night , maybe the software doesn't like windows 8.1 entirely or maybe I was just tired) but anyway , then I can start and run the car on petrol and drive until it has another dummy spit and hopefully be able to pull over to scan for errors again before switching back to gas .
    Maybe an idea to remove the Mace performance chip for the time being just to be sure altho once again it runs good on gas with the chip installed (different octane rating tho) .
    I should add when it starts to crap out , say trying to mildly accelerate from 57-58kph up to say 65 it starts to shudder almost like a corrugated dirt rd and this gets worse too .
    Now Nutcracker has me thinking too about this other sensor which sounds . More reading to do yet , cheers guys .

    Oh , thanks Dirtyhands too by the way , I did ask the mechanic at work about that today but he said the symptoms dont match the fuel regulator .
     
  10. GMDriver

    GMDriver New Member

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    i'd doubt it seeing you have no fault code for the coolant temp sensor,
    The other thing is to look at the temp in dashboard mode on your laptop, if its a stable temp (around 80 deg) fully heated up, & not fluctuating the sensor will be fine.
    Go with the codes its telling you, its running rich 1 side....
    Good luck
     
  11. billythakid

    billythakid New Member

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    Don't rule out an ignition fault as the gas is colder and atomised better than petrol .
    Maybe a cracked plug or lead not firing when hot
     
  12. lignum1966

    lignum1966 New Member

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    Thanks again folks , my day off this arbo so I'm gonna try to change the o2 sensor on the left because of those errors to be sure . Funny enough tho after work yesterday it took me 3 or 4 mins to enter the Port River Expressway , running on gas , I accelerated toward the 90kph speed limit and around 60 or so it started fartin about and didnt really wanna go above 70-75 , literally lost acceleration and power until I backed off before the traffic slowed to it's usual crawl . Anyway , after a 10min crawl the traffic opened up again and the car was felt normal again . This hasn't happened before .

    I tried using Tunerpro again but when I bring up the send command it doesn't say clear anywhere , just a blank selection box where I assume it should say clear . I can only clear my airbag light using a different command .

    After yesterdays display on gas after work I'm starting to think biilythakid is also on to something right there
    Silly as this sounds can the BCM have anything to do with it , it's just that before I got in the car after work yesterday the smartlock system wouldnt let me in so I had to unlock manually and then turn alarm off by turning ignition on , prolly coincidence as that happens now and again with the locks but thought I would mention it ..
     
  13. dirty hands

    dirty hands Active Member

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    now you have gas and petrol problems

    switching between the two fuels gets confusing --- when both behave differently

    yes looks like electrial problems but where

    if Tunerpro isnt giving you eneough answers..... is it time to take it a dyno or gas expert
     
  14. billythakid

    billythakid New Member

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    By your last post I'd start looking at the TPS first as a culprit , then the plugs / leads / coil packs/ DFI
    TPS is relatively cheap to swap out (under $50 aftermarket

    Also a dying battery will cause havoc with electrical things and do some really weird **** to sensors
     
  15. lignum1966

    lignum1966 New Member

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    Ok dunno about the one off (hopefully) gas problem , but yesterday arbo I changed the o2 sensor on the left but didn't have time to test the car out properly .
    Anyway , sitting home last night I was thinking I tried swapping out the Mace Ecu chip and the standard one before I changed fuel pumps and filter and whatnot to no avail but hadn't since doing the pump . So I swapped the chip out for my standard VT chip and drove to work today , and back home after without incident or drama , other than the 200 knobs on the road between home and work . So narrowed it down to 2 hopefully . Put the Mace chip back in tonight , took 5 or 10 mins cruising to get up to about 80 degrees C and ran ok for about 5 mins or so at that temp or up and down 1 or 2 degrees , shortly after it started running a little worse and starting to miss a little and lose some power . Went home , swapped the chip out again and put my standard one back in . Went cruising , car was already warm but ran on petrol no problems at all , showed no signs of playing up after a cruise so it seems the Mace chip is the culprit . Probably not suitable for dual fuel or something like that . If I ran gas only I would keep it in the car as it seemed to have good potential for the small amount of money and certainly made the car better on gas . Anyway hopefully solved (touchwood)
    Thanks to all who offered me advice/ideas !


    Thanks al for helping

    Forgot to say , battery neg was disconnected between every chip swap !
     
    Last edited: Apr 23, 2015
  16. lignum1966

    lignum1966 New Member

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    Gee culprit might not of been a great word either as I dont think theres anything wrong with the chip and certainly wasn't havin a go at the Mace company , I think they do pretty good value bolt on mods for amateurs like me to learn and gain a little with !
     
  17. V6formethx

    V6formethx New Member

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    Why do you ask that? My old mans has the same fault code 57 and has backfired on gas twice now, he is having to leave it on fuel but still not running ideally and fuel consumption is real bad.
     

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