sc400 Rev cut a 3750 RPM HELP URGENT

[ndgcpr]

Wasn't there another thread on this same topic? do a search...
They were saying the ecu's in limp mode etc....although that doesnt make sense if you've changed the ecu.

Yes my friend and i had a post up with respect to a 1JZ. The outcome? We replaced the fuel pump, exhaust and lots of other things. I drove it and really felt like a soft rev limit. The problem that we couldn't work out was that it did not happen free revving. Put it in neutral and rev it up (if your comfortable going this high in neutral).

Anyway the outcome of ours (which may stop you doing what i just said) he was eager that it would boost and rev high in neutral. He reved it up quite a bit one day and the engine is no longer a happy camper. it is now making awful noises so it is obviously preventing higher rev's for a reason...

[Vios-GT_07]

yeh but he says he can chuck it into neutral and it would rev up to 4000 rpms.. but pressing the accelerator doesn't do anything.. it'd just come back down to 3750 and cut out..

this might also sound pretty stupid but have you checked TPS and throttle cable?? and also can you rev it up past that mark in N??

[Hen]

This is purely regurgitating info I have read on the net somewhere, but I thought a cut at about 3800 was linked to the speed sensor playing up.

This is because 3800 in top gear is 180km/h. So if the speed sensor input isn't connected/dodgy, then it is limited to 3800 in all gears, just to ensure you still can't break the 180 limit.

I'm unsure if you have checked this out already or if its applicable to your problem, but good luck.

Hen

[Buttocks]

how do i check the speed cut sensor/?

[thechuckster]

disconnect speed sensor cables on back of gearbox - see if problem symptoms change or remain the same

[MacroP]

1UZ hard cut is 6500 afaik.

I've hit it once and it sure didn't feel like a soft cut.

Hey man, yep certainly a hard cut. Mine's hit the rev limit a few hundred times now I reckon . Bounces happily from 6200-6500 on a 2-3 Hertz cycle roughly.

As for my MX83(with a Soarer motor) with a 3.9 diff (I think this is the same as the Soarer) the 3rd gear rev count out is around 165km/h. So it's 4th gear for the 180km/h Speed cut.

[CrUZida]

For 3800 to be the speed cut, you'd have to have a ~3.6:1 diff ratio (given stock 205/65/15 tyres).

3800 with a 3.9:1 diff is <170kph.

I've also driven my car (with a Soarer ecu) with no speed sensors connected, and it went well past 3800rpm.

[chris davey]

disconnect speed sensor cables on back of gearbox - see if problem symptoms change or remain the same

I don't think he would be able to change out of 1st gear if he does that.

[bansheebuzz]

Where are you located. I am an auto elec with a business on the Gold Coast. Done a few 1uz conversions now and am pretty familiar with them. I can take a look if you want.

[Buttocks]

I've been in contact with Trial in Japan and they seem to think there speed cut defender will work, but it hasn't been confirmed that its got anything to do with the speed sensor. Anyone know how the speed cuts work?

[CrUZida]

Speed cut defender just makes the ECU think the speed never goes over ~175kph.

It will play havoc with your shift changes though.

But if you have changed ecu's, and you don't think its a sensor causing it, and you can't find anywhere where the wiring has been tampered with, then I can't see a speed cut defender working.

[sideshow]

the speed signal it cuts is the one that comes form the dash speedometer
so that means yr sc400 should have the sp2 signal still there
speed signal is just an rpm pulse that gets quicker when you go faster in speed so it basically knows how many pulses make 180km and stops it goin that fast to the ecu

im pretty sure its not a speed related prob

if the engine hits a hard rev cut and an exact rev limit and cant go thru it then its def a prob with the ecu or some elcetrical unit in limp mode

if it was mechanical usually the prob will vary when it happens depending on many things

like i said before ive had similar probs but at 2400 rpm cutting hard but this was a 1uz into a ma70

just remember wherever u take it they might sped 2 to 3 days on it and might cost u over 500 or so to fix the prob

the sc400 has ecu for fukin everything so unless u can try them all you will take years to fix it

problems like these are very hard to fix by asking on the forums unless someone has had the exact problem

just take it to toyota they know what to do because they are all experts hehehehehe

[Vios-GT_07]

just take it to toyota they know what to do because they are all experts hehehehehe

i've taken it to the local toyota dealer who have fault check the car with the australia 1uz diagnostic tool (only shows about half of what it should as nobody here has a proper *** one) they found nothing
We have changed over these parts
ECU
Fuel Computer
igniters
AFM

this is getting really interesting

[CrUZida]

He (sideshow) said that in extreme sarcasm Vios.

[sideshow]

i sure did hehehe

anyway im off to make some money before i go on holidays