sc400 Rev cut a 3750 RPM HELP URGENT

[buttocks]

Heres the problem
I own a sc400 1991 model imported for Japan to Australia
When i picked it up it was hitting a rev limiter at 3750
Now the car is absolutely stock
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

Its a real horrible problem that no-one here can answer and its driving me mad, its 100 percent like the rev limited that should be around 7000rpm
i've been told to check the fuel pump now, but if the fuel pump wasn't supplying enough pressure it would hestitate but the car drives perfect except for the rev cut.
I also found today if i get to 90 kph and knock it back into 2nd it will go above 4000 but cuts out until the revs go below 3750 again and off it goes as normal, but a fault code comes up in Japanese which i translated to engine electrical system (kind of a broad statement)
Any help would be life saving

 

[Lextreme II]

I think there was a very similar thread like yours recently posted. Look around in this section.

 

[buttocks]

Thats my thread, its still a problem. Thought i better start another as it seems you guys are my only hope of finding the problem

 

[Lextreme II]

I hope this link will help http://www.lextreme.com/Lex DX.pdf

 

[Mr.Phreak]

Don't want to step on Lex's toes or anything, but you may want to check out http://soarercentral.com/ which has alot more Soarer specific information including how to access the On Board Diagnostics.

Also the majority of users are from Australia so you might find someone close who can give you a hand.

 

[Lextreme II]

I love that site.... not stepping at all. As long as we can help our members then I am very cool with any other sites. ALSC is a great place to get info too. I think eight Zuffen, Cribbj or Kdog should have some info on this strange problem. Now the question I have does the engine rev at Park (P) or it wont rev when in Drive (D)?

 

[buttocks]

I mechanic friend of mine suggested a Fuel cut defender, would that work??

 

[Mr.Phreak]

If it did, it would only be a bandaid solution which may cause further and more serious problems.

Sorting out what's wrong might take a little longer or cost a little more, but it should work out better in the long run.

 

[Edwin_S]

Try another Throttle position sensor.

 

[buttocks]

if i haven't got one handy? is there another test for the throttle position sensor

 

[zdw]

sound like a govoner

 

[Edwin_S]

Yeah, you can measure the resistance of the sensor, but i don't know exactly what pins you have to check.. the wiring manuals that where here are gone for some reason, I can't find the anymore

Basically, the TPS has 3 or 4 pins. 1 pin that has 5 Volts on it, 1 ground, 1 signal and optionally 1 for full throttle. What you need to do is measure the ammount of Ohms between the 5 Volts pin and the signal pin. You'll need to figure out wich pin is what by your selve, i'm not near my car right now and the diagramms are gone.

What you should read is something like 5K ohm when the throttle is closed and when you open up the throttle, the resistance should decrease smoothly down to about 1,5K when full throttle. I don't know the numbers for the 1UZ exactly, but this is what I measured on a 1JZ-GTE.


Hope this makes sence as I'm from Holland and my technical english is a bit rusty

 

[Lextreme II]

There are few diagrams on measuring the TPS somewhere in this forum

 

[Edwin_S]

Yeah, I found this for you:

http://lextreme.com///forums/showpost.php?p=39444&postcount=2

The search function is your friend!

 

[Zuffen]

If you car has traction control you can swap the TPS/TC switches over. This will tell you if it's a faulty TPS or not.

My feeling is it lies in the hi and lo speed fuel circuits.

You could try disconnecting the feed to the fuel pump and running a temporary 12v supply to the pump and see if that fixes the problem.

What happens when you floor it in a high gear (other than kickdown) does it get up go like it should or does it struggle a little. If struggling it would indicate the fuel pump is staying at low speed.

 

[zdw]

:Flush: when i get the chance right now im in the middle of rebuilding a volvo 850 station wagon that the valve stem seals were leaking not to mention the other 40 cars i have to take care of but thankyou for your help

 

[zdw]

what engine is in my pic? come on give it a guess

 

[Zuffen]

I'll take a punt on a 351 in an early Mustang.

The avatar is too small to blow up to get a decent look.

 

[GSMnow]

As far as I remember from the LS400 manuals (I don't have them here) the 1UZ has a rev limiter and a top speed limiter. My guess is that the top speed limiter is being triggered. If your wiring harness is completely stock, I would look for a point where it may have been pinched or cut. I would have to do some math to see if it works out, but if the VSS (vehicle spoeed sensor) is getting the noise from the ignition, could it be telling the ECU you are going 155 MPH and shutting down the motor? Thje engine RPM is read from the 12 tooth wheel on the front of the crank, if it was getting a double speed signal, the motor would not run well if at all due to the spark and injectio running at the wrong times, but the VSS being wrong could only really alter trans shift points and the speed limiter. Being a 1991, you have 2 x 4 cyl dizzys. This would be 4 pulses per revolution of the cam, or just 2 per rev of the crank on each dizzy. That pulse rate on the VSS seems pretty low as the VSS 2 is 4 pulse per drive shaft rev. The SPD (VSS 1) is taken from the speedometer. On my LS400 setup, it take the signal and divides it by 5 to the ECU, so it is a lower pulse rate, just a little more than 1 per revolution. Could the tach signal be getting into that? DO you have access to an osciloscope? If so, probe the VSS SPD leads on the ECU. There should pbe no pulses if the car is not moving. Does the engine rev limit in park or neutral? When the car is moving, the pulses should get faster with road speed, not engine speed. Also check the IGT and injecttor signals when it rev limits. Does it lose the IGT pulses or injector pulses, or both? Also check IGF, this is a pulse back from the igniter when a spark actually occurs. Loss of IGF should set a code.

I hope this helps,
Gary M.

 

[zdw]

1966 shelby mustang gt
very good