ABF in MK1 Irregular power loss at full throttle.

Discussion in '16-valve' started by chz, Nov 1, 2020.

  1. CHZ

    chz New Member

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    I have a Mk1 racecar with ABF and abf ecu and injection, improved chip ,improved cam and head mild flow, still has K-jet high power fuel pump. Seems to have developed a miss or power loss irregularly but always inconvenienty for races. Unfortunately the loom i got with the motor was missing the obd11 port for scanning. Retained Mk1 wiring for everything else but the engine. Initially ,for 1 race, engine ran fine. Replaced plugs, coil and spark plug leads. Made sure oil level kept highish- is there a oil level sensor which switchs to limp mode ?? Kept fuel level high to maintain flow .Replaced fuel filter and cleaned air filter. Anyone got any ideas. Can Rubjonny or toyotec help. What wire is the obd11port usually, colour and spot on plug for me to retrofit ?
     
  2. rubjonny

    rubjonny Administrator Staff Member Admin

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    diagnostics wire to ecu is ecu pin 43, pop that to port pin 7. then live to 16, earth to 4. get the diagnostic codes read and work from there.

    if you dont see anything obvious intermittent loss of power can be hard to diagnose, how bad is it exactly? we talking slight feel of engine holding back or dramatic? in the past I've found ecu relay can cause random power loss, and bad ecu earth connections can make it do odd things such as relays buzzing in time with isv and rev counter going nuts. if you loose the ignition live to the ecu it can do odd things also, this feed is shared by the isv from the factory.

    check the wiring round the back of the engine to the throttle position sensor and idle switch, this will usually be baked hard and insulation cracked away. theres also a 2 pin plug for the breather heater which can be deleted it has a black and brown wire. the black wire is tapped to isv power and often the cause of isv fuse blown. brown earths straight to head so easy to remove. while there check the operation of the idle switch, mine would operate randomly while driving due to it failing internally, which would make ecu try to go into idle mode and caused engine to hold back.

    crank sensor always a top suspect, make sure wiring to it is good and its a good quality part. oh and look at the vacuum hose from inlet to ECU, make sure thats not split and you have good quality hose as the cheap ebay braided stuff can often go porous. I only use genuine VW vacuum hose now if you want the fluffy OE type, pricey but worth it.
     
  3. chis New Member

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    Thanks John, we'll try all that. The power loss is substantial when racing. about as much a loosing one cylinder. If I back off the throttle it seems to come back, but not always. Seems to occur mostly after coming out of corner and planting the foot.However at another corner at full speed doesnt occur which kind of suggests fuel and oil levels are not to blame. Sometimes if only do 3/4 throttle, hard to control the foot, it doesnt occur, but not always. Hence my thought about fuel levels and oil levels, however with both full , no change.
     
  4. rubjonny

    rubjonny Administrator Staff Member Admin

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  5. chis New Member

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    Yes original fuel tank, I saw the post and discussion about the fuel tank swirl pot and thought, thats another thing to check. But what can you do to repair the broken seals. Sounds like nothing except replace the tank entirely. Bit of an issue in NZ with very few if any available parts for Mk1's. You are right, no chance to hear the fuel pump when racing although I suppose I could set up a temporary light to show when fuel pump is running.
     
  6. rubjonny

    rubjonny Administrator Staff Member Admin

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    one way round it would be to fit a pre-supply pump and external swirl pot, though space would be pretty tight under there. if its still got the fuel accumulator that can be binned if it helps.

    an amp meter would be more useful inline I think, then you can see if the pump starts drawing more current if so that would suggest its starting to strain. on that note how are you triggering the pump, did you wire up the ecu to trigger a 67/80/167 relay in the fusebox or did you leave the original kjet relay in there
     
  7. CHZ

    chz New Member

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    The original kjet, could that be a problem, I thought that would be an all or nothing affair. Years ago I had that, mysteriously the fuel pump would stop on the exact corner that precedes my present loss of power !!! Finally we found that there was an extraneous wire that shorted and blew the fuse only when the engine twisted a certain way on that corner. We cleared out all extraneous wires hiding behind the motor and the issue stopped. Maybe the relay is aberrant and failing ?? Replacing it would be a good idea perhaps.
     
  8. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    I also had a client with an ABF fitted to a race car, on the OE Digifant 3, with a Eprom by me in the ECU.
    That had similar problems, and we solved by junking the MK3 Coil and fitting the old TCI-h and coil.
    Of course, it is unknown what you specific problem is without seeing the car. I would suggest to get the diagnostics working.
    Often I have seen crank sensors, of unknown brands failing after a minute of 3 of operation. You can get no codes also, as the ECU still see it as a valid electrical input.

    More information required.

    Regards

    Ed.
     
  9. CHZ

    chz New Member

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    Yes, i'll get some codes to start with, one step at a time. So with the TCI-h and coil do you go back to the old dizzy as well ? Unfortunately, when i got the ABF didnt have a full clear loom, someone had ,had a fiddle around. I then kept the Mk1 loom / fuse box for the rest of the car which was actually in good shape, no rust and leak damage and patched in the engine wiring for the ABF - took forever. As a punt I bought a couple of so called performance chips for Seat abf from europe on ebay, then after a bit of head work, rings and a tickle and a cam-Newman PH2 VOLV/272/420H with assoc lifters and double springs,[ not wanting to do too much in one leap and doing circuit and Targas and chatting with David for advice], we tried out the original and two performance chips on the dyno. The original and one performance chip were not good , but the other was great . went from 150hp to 185hp at crank and torque to 158 crank. I do have a large cone filter, any issues with that ?
     
  10. chis New Member

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    Codes havent helped . However the vacuum line was loose and probably loosing vacuum. If that was the cause what would the symptoms be. Characteristically, the power loss occured after a deceleration into a sharp corner and then the power loss came under the heavy acceleration out of the corner. Would that be characteristic of manifold pressure vacuum loss ?
     

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