lateralnw

I'm having lots of fun at the moment. Take off at the lights and the car bogs down barely accelerates with a slow increase in revs until it hits about 2700 rpm then it just launches in to insane mode - max rpm- (which is a lot of fun but a little dangerous and really pisses off the other motorist) SC400 uzz30 1UZFE
This can happen even if I'm not putting my foot through the floor. Firm but not flat out acceleration will also have the same effect.

I replaced the spark plug leads and this seemed to have helped but the problem feels like it is coming back. It never really went away but it did improve. I also replaced the plugs, granted only copper ones at this stage but they work.

Is it possible that the auto trans has an effect on the acceleration as I did have some big problems with the trans a while ago and have managed to keep it working until I get some $$ to replace it. The clutch material is slowly disintegrating I suspect based on my last check of the trans internal oil filter. Little black particles showed up when I filtered the old trans fluid.

I replaced the coils also.

I have also replace the capacitors in the ECU except 3 that are hard to get at and looked liked they where ok. (I know that is not the way to test capacitors) The ECU had some circuit board damage and one of the surface mount resistors and cct track was stuffed which I replaced.

I don't understand how the car can be a pain at slow speed ( no torque) but launch when I kick it down and it is above approx 2700~3000 rpm

Any help would be appreciated.
I did search the forum but didn't really know what the best search words would work.

Ali SC3

iTrader: (10)

those are symptoms of a bad ecu or an intermittent spark issue. I would guess the ecu.
generally it causes overfueling, so in part load or lower rpm's itll wash out the spark and hesitate, but when you get to the rpm where the motor can handle the extra fuel it'll actually run pretty decent.
not saying that is 100% it but it sounds like an ecu issue. sometimes once the board is damaged its not really salveagable even if you replace the caps. you could have also blown the injector driver.

also don't forget there is more to the ignition system then plugs and wires, the 1uz has 2 distributors that each have a cap and rotor that should be replaced every once in a while.

eefmydee

I already know you made one mistake when you did not replace those three capacitors. even if they look good they are still bad go back and replace the other three

lateralnw

Thank you for the reply, I did wonder if the ecu/injector driver may be intermittently failing.

Unfortunately I don't have access to a loan ecu.

I have been reluctant to touch the distributors as I haven't found a how to. I did wonder if at low rpm there is weaker spark which makes it harder for the spark to jump across the rotor buttons?

I guess I could revisit the ecu and do the other caps and while I'm there check the injector driver.

Anyone know which chip / chips it/they are? I figure it will be a control chip and then driver transistors or FETS connected to a heat sink.

And a how to, to change the rotor / distributor correctly?

Thanks.

lateralnw

Lol, Point taken. Damn it :-)


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Ali SC3

iTrader: (10)

at that point I would try swapping with a working ecu. there are companies that do a rebuild service, but if the board has damage I personally say toss it and find a replacement ecu and then have that one serviced if necessary.

a weak spark from a distributor cap rotor issue generally wont clear up in higher rpm's and would likely still misfire.
still something to do maintenance wise for the future, you just remove the distributor covers then the caps and the rotor comes off with a screwdriver. one side is easier than the other.
It sounds like you are overfueling which tends to become less of an issue and clear up with rpm's or opening up the throttle some.

It could be something else but since you have had issues with the ecu in the past it sounds like its related.

lateralnw

After finding the problem it seems logical that above 3k rpm approx the car works fine.
Fuel related and as it turned out fuel ecu.
Intermittent fault where fuel ecu would not supply fuel pump enough voltage below 3k but above that it must switch over to full voltage and wham off it goes.
Bypassing at the moment but have another fecu I'll fit that should prove my thereoy.

Just for fun replaced other main ecu caps but it made no difference.

lateralnw

Update,
I also found later on that the fuel pump was starting to fail. When I finally got around to replacing it I noticed that the filter that is attached to the fuel pump was so blocked that I was lucky any fuel got through. Just for fun I held up the old filter and the new filter against a back light. The old one you could't see through it and of course the new one you could.

Since I replaced the fuel pump I haven't had any more problems ..... at least not with the fuel!
Unfortunately the replacement fuel ecu I managed to remove from a wreck didn't work so I am still running using the bypass wire.

I did also pull out the main ecu and went over my soldering. As some of the tracks had gone I created new ones but didn't notice that I had connected one pin to the wrong track. Its now fixed and the ecu seems to be working perfect.