Hi I've been having a problem for quite some time. Usually on part open throttle the car occasionally hesitates and jerks for a second and then picks up great and may repeat this for a few times. Sometimes its not that obvious but I can tell the difference. The problem lasts for a few days and then seems to go away and come back a few weeks later at random. Around the time I feel it the car in general feels a lot less powerful. I've been trying to diagnose the problem for quite some time now. I dont get any ecu errors from the diagnostics and I've changed the following already:
Converted to manual(didnt help)
Changed spark plugs and plug wires
Changed fuel filter (in engine bay)
Tried octane boosters and fuel and injector cleaners regularly.
Rising Rate Fuel Pressure Regulator
Cleaned all sensors like TPS etc.
Does this def sound like a fueling problem or could it be something else like sticky valves etc? Could bad gas cause such serious issues? I though the car would just retard timing in a case like that? I ask this cause the gas we get here is hit or miss and v.far from the japanese standard. The car seems to work great other times and i get decent mileage and no oil leaks. Its a 97 GX btw. Any help etc would be appreciated.
Car Jerking on Acceleration
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RedlineGX
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RichardH
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First of all, this post was up on the UK FTOOC forum...
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Important bit for others with FTO jolt problems:
Andy seems to have found why the car jolts at low speeds. At a certain throttle setting the stepper "pulses" the throttle body control causing the revs to die then jump back because it has moved away from that "certain throttle setting". In neutral gear this point was around 2000 - 2500 rpm, but under load its around 1500 - 2000 rpm.
I dont understand it, but this is apparently being caused by a "high resistance" wire from the stepper and ECU causing incorrect feedback to the ECU. So at certain points the stepper gets "pulses" from the ECU, which causes the stepper to drop the revs.
Its quite funny in neutral when you listen as it revs happily at "the certain throttle setting" for a couple of seconds, then when it dies back for a fraction of a second it sounds like its backfiring.
Also, apparently due to this wire having an incorrect high resistance (I still dont understand) the ECU doesnt bother altering the revs for when the AIRCON is on and doesnt bother retarding the idle speed when you turn the ignition off. So it never goes back to the COLD setting, but is actually stuck at the hot position.
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Dunno if that's exactly what you have, but it did ring a bell.
Next, connect up the little engine ECU diagnostic wire and confirm there are no fault codes in the system (see 'Workshop' section at http://www.ftowa.com.
- Rich
-----------
Important bit for others with FTO jolt problems:
Andy seems to have found why the car jolts at low speeds. At a certain throttle setting the stepper "pulses" the throttle body control causing the revs to die then jump back because it has moved away from that "certain throttle setting". In neutral gear this point was around 2000 - 2500 rpm, but under load its around 1500 - 2000 rpm.
I dont understand it, but this is apparently being caused by a "high resistance" wire from the stepper and ECU causing incorrect feedback to the ECU. So at certain points the stepper gets "pulses" from the ECU, which causes the stepper to drop the revs.
Its quite funny in neutral when you listen as it revs happily at "the certain throttle setting" for a couple of seconds, then when it dies back for a fraction of a second it sounds like its backfiring.
Also, apparently due to this wire having an incorrect high resistance (I still dont understand) the ECU doesnt bother altering the revs for when the AIRCON is on and doesnt bother retarding the idle speed when you turn the ignition off. So it never goes back to the COLD setting, but is actually stuck at the hot position.
------------
Dunno if that's exactly what you have, but it did ring a bell.
Next, connect up the little engine ECU diagnostic wire and confirm there are no fault codes in the system (see 'Workshop' section at http://www.ftowa.com.
- Rich
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RedlineGX
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Thanks for the reply. Yes I did see that post but I'm quite sure that its not my stepper motor since it happens throughout the reve range. I am becoming more convinced that the engine is starving for fuel which is obviously a very bad thing. Today the jerking is not there but I'm way down on power and the poeer band feels very up and down. I did hook up the ECU and no codes. Gonna have to get it checked out by someone but I hate carrying my car to garages since they all seem to be completely incompetent and I usually end up disappointed and some cash short and teaching them something new about FTO's! 
Oh well thanks guys, I'll let you know if I find the problem.
Oh well thanks guys, I'll let you know if I find the problem.
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RedlineGX
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HiRAEdd
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Injector cleaners
For what it's worth, I've used the fuel additive injector cleaners several times both on my old car (an Excel) and now my FTO. In all cases I've had significant performance gains after each use. The FTO when I bought it actually would sit at the lights, almost conk out then rev up high before repeating the process until I started to accelerate away. I added injector cleaner in Sydney and by the time I'd gotten to Brisbane it had stopped happening and has never happened since.
I'd certainly try it, it's a very cheap thing to try so if it doesn't change anything for you, you've really lost nothing for your effort.
I'd certainly try it, it's a very cheap thing to try so if it doesn't change anything for you, you've really lost nothing for your effort.
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RedlineGX
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Well as far as over the counter injector cleaners go, I think I've tried about every one available sometimes two in a tank....but the problem goes and comes back...so maybe its time for a more professional cleaning. Problem with something like this is that its so hard to diagnose. Could be anything from a faulty pump to a loose wire 
Thanks anyway.
Thanks anyway.-
RedlineGX
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RichardH
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RedlineGX
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OK well changed gas and put in heaps of octane booster and alos a bit more injector cleaner. Wanted to see if it was possible I just keep getting dodgy gas. I then reset the ECU. At first no difference but after about 40/50 km the car feels great again 
So once more I will probably forget the problem till it comes back again. In any case I'm going to get a professional fuel and intake cleaning on Monday and get a compression and lambda sensor test done the same time. Thanks for your help guys and I'll keep you posted.
chris
So once more I will probably forget the problem till it comes back again. In any case I'm going to get a professional fuel and intake cleaning on Monday and get a compression and lambda sensor test done the same time. Thanks for your help guys and I'll keep you posted.
chris