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Help/advice pls: intermittent misfire/rough running in T3

Discussion in 'T3 & T4 Tech Help Clinic' started by nick page, Apr 3, 2018.

  1. nick page

    nick page New Member

    Messages:
    3
    Location:
    perth
    Had 1991 T3 "Crush" serviced last week before our family Easter trip.
    About 100-150km later he developed a very slight misfire, more of a hesitation at first. Over the next 500kms (over 3 days) it's become worse, the change from 1st to 2nd, and 2nd to 3rd will often cause you to bog down, lose power, i've snatched the next gear up and he's carried on valiantly. He sat on 100-110kph in 5th without any problem, and even accelerating in 4th was OK. Tick over/idling is smooth and revving in neutral is OK too.
    Today we replaced the fuel pump and filter, changed spark plugs, checked the leads, rotor arm and dizzy cap. Checked the timing. Even swapped MAF with another vehicle to try and isolate the problem. No joy. The minor service last week incl. new belts. new air filter, new oil filter and engine and gearbox oils.
    Anything else to check?
    Thanks in advance.
     
  2. Grantus

    Grantus Well-Known Member

    Messages:
    14,323
    Location:
    Southern ACT
    Unplug the O2 sensor, and see if it helps. :rolleyes:

    Check that all 4 sparks are actually firing.
     
  3. nick page

    nick page New Member

    Messages:
    3
    Location:
    perth
    thanks Grantus, will do. I think all four are firing 99% of the time as he'll cruise along normally. Maybe with a very slight fluttering over about 105kph.
    Problem seems to be under load, up inclines with low revs etc.
     
  4. Barry

    Barry Well-Known Member

    Messages:
    2,535
    Location:
    Abbotsford NSW
    I would be trying a new coil.
    The "underload" makes me suspect this.
    After that can you borrow a dizzy?
     
    Shredhead likes this.
  5. Barry

    Barry Well-Known Member

    Messages:
    2,535
    Location:
    Abbotsford NSW
    Also check timing. Could have been played with during service
     
  6. nils

    nils Well-Known Member

    Messages:
    1,368
    Location:
    newcastle
    Barry is on to it, Definitely sounds ignition related.

    I would be rechecking my spark plug leads (possibly in the dark, looking for arking)

    Seeing as you just had it serviced, there is a pretty good chance they have been damaged or worse yet replaced with inferior brand leads.
     
  7. syncro

    syncro Well-Known Member

    Messages:
    8,913
    Location:
    Southern Highlands
    Nils is on to it.

    Genuine type leads very rarely fail. It is the connectors which have a carbon resistor in them. Check them with a multimeter.
     
  8. beerboy

    beerboy Active Member

    Messages:
    990
    Location:
    Sydney
    Mine used to cut out pulling off the lights. no pattern. went done vanagon sydnrome route. But think the cause was a new coil that got hot and failed intermitently. New bits can be worse than the old. I went back to the old coil no problems. new coil leads are meant to be an issue too. good luck. i knew it was the new coil as it eventually failed
     
  9. syncro

    syncro Well-Known Member

    Messages:
    8,913
    Location:
    Southern Highlands
    This is a big problem with owners doing the Chinese VW conversions for no reason.
     
  10. Luckyphil

    Luckyphil Well-Known Member

    Messages:
    5,504
    Location:
    Gosford
    Phil do you think people wake up in the morning & think " I will do a Chinese VW Conversion"
    What do you mean by this, seems a bit confusing to me and possibly others so please explain what you mean. Sure there are substandard parts out there & not only from China but cost & availability are a factor so rather than ridicule we should help on this forum with constructive advice on where to buy parts from as you very well know VW no longer sell the majority of the parts we need to keep out T3's running.
     
    Syncro27 and Wayne murray like this.
  11. Luckyphil

    Luckyphil Well-Known Member

    Messages:
    5,504
    Location:
    Gosford
    This is a tricky one & has me stumped however If you can swap out the ECU with a known good one might help. Or only other advice is that the fuel outlet at the tank is blocked.
     
  12. Gerry and Robyn

    Gerry and Robyn Active Member

    Messages:
    565
    Location:
    Lilydale Vic. Australia
    Hi Nick,
    Have you had the injectors checked for correct spray and atomising?
    Gerry
     
  13. robbie0810

    robbie0810 Member

    Messages:
    76
    Location:
    Gosford Australia
    Hi Nick, how old is your fuel tank? We had some very similar issues recently with our '89 and I suspected ignition too and changed a few things. It was just as you describe, sometimes losing power but ticking over fine and generally cruising on the freeway fine. It was worse when heading up an incline, say 2nd or 3rd gear but the revs not high enough and no power to push through, just seemed to choke. In the end, after much online research, I added a small fuel strainer between the fuel tank and the pump, as well as a new fuel filter. As soon as I took it for a run it was much better and when I looked at the strainer, it had rust deposits in it. I emptied the old fuel filter (year old maybe) into a glass jar and the fuel was clouded with fine rust sediment. I have since replaced the fuel tank and it's been running great for several weeks (including a trip from Gosford to the Gold Coast and back...
    Good luck!
    Rob
     
    Syncro27 and David H like this.
  14. beerboy

    beerboy Active Member

    Messages:
    990
    Location:
    Sydney
    I think he has replaced the tank with a 2nd hand one. old tank was the problem I think. nick nick.........
     
  15. Syncro27

    Syncro27 Well-Known Member

    Messages:
    5,792
    Location:
    Terrigal, NSW Central Coast
    I had a similar problem with my T3 2wd bogging down under load when my fuel pre-filter was totally clogged with rust.

    Ran fine when not under load as they can run of the smell of an oily rag - but under load they studder and have bugger all power. I knew my tank was full of rust as it sat for 6 years under a tree - the fuel in it turned to resin and helped corrode the tank.

    Replaced the filter and later the whole tank and it has run great since.

    It struggled a bit for power on hot days so I replaced my coil and that is all good. Electrical and heat dont mix very well and things often fail.
     
    robbie0810 likes this.
  16. beerboy

    beerboy Active Member

    Messages:
    990
    Location:
    Sydney
    I am just replacing the tank again. I had the same problem scott wouldnt run under load. no pre filter so pump gone west. garage charged me 1500 for new 2nd had tank and clean injectors. basically a pile of work and expense. that was 6 years ago. hoping new tank a good investment.
     
    Syncro27 likes this.
  17. wobbly dugong

    wobbly dugong New Member

    Messages:
    11
    Location:
    Innisfail FNQ
    Seen it a lot where i live- Wet Tropics , rainy and humid,,,water in the fuel. sometimes when the service stations tanks get low the fuel the pumps supply can have heaps of water in it , ( comes from condensation, and lack of proper maintenance)),changing the tank will fix the problem but possibly fully draining the tank will do the trick. most older tanks will have rust in them and wont worry the system, Its the water buildup in the tank that will make the motor run like S++t , I run a pre filter with a bowl separator before the standard fuel filter and am constantly amazed about how much water I drain out of it from time to time., especially when I fill up at dodgy service stations in whoop whoop.
     
    robbie0810, Syncro27 and Luckyphil like this.
  18. wobbly dugong

    wobbly dugong New Member

    Messages:
    11
    Location:
    Innisfail FNQ
    oh and by the way the only way I know of to fully drain a t3 tank is to remove it and go from there., there is also so many gromets and pipes entering the tank that is is also possible for water to enter from many places during rain or wet roads etc. anyway something to think about. water and fuel = lots of problems that could have you chasing your tail .
     
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  19. Beau

    Beau Member

    Messages:
    95
    Location:
    Sunshine Coast, QLD
    Hey Steven. Any more info on this prefilter setup? Thanks
     
  20. wobbly dugong

    wobbly dugong New Member

    Messages:
    11
    Location:
    Innisfail FNQ
    Sure, Straight after the tank I use a Ryco universal fuel filter, it has a cartridge element in it and a glass bowl separator on the bottom. I use the most coarse filter element i can get as a strainer and i still use the in line filter , which is after the fuel pump as its designed to finely filter the fuel for the injectors.
    The bowl catches any water that may be in the tank from condensation ,dodgy fuel, or leaking grommets , pipes etc, It can be emptied when necessary by opening a cock in the bottom of the bowl.
    This means that fuel passes out of the tank , gets strained , has the water removed and then passes into the fuel pump , then goes through the factory installed fuel filter for delivery to the injectors.
    Main benefits are :
    The fuel has the water pulled out of it before going to any other part of the fuel system.
    The strainer INSIDE the fuel pump does not get blocked up , (longer life & better flow) and better delivery pressure.
    The factory filter (after the pump) does not have to be changed as much and can do its job better, as it is a very fine filter designed to look after the injectors and These too collect water if it is present in the tank and restrict fuel flow.
    The injectors also get a longer life and perform better , especially during long periods of non use.
    Drawbacks are a small added load to the fuel pump ( imperceptable) and the bowl must be emptied when its full of water, otherwise you might as well not have it installed .
    Sorry for being so long winded about it but it is surprising how much water I drain from my bowl! and I do like to ramble on ! Water in fuel could harp on about it all day.
     
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