Cant get to Redline

[Simple]

My st162 is reluctant to get to 6750 redline, i get good power from about 3500 to 5500 but power REALLY drops of way too much from 5500 to 6750, and it sounds like its staining?

what could be causing this? bad oil? bad spark? bad everything?

thanks

[thechuckster]

could be bad everything from being regularly taken up to the redline?

[hamgatan]

yeah could be anything..

clutch perhaps? cant hold the torque at certain revs? does it feel like its slipping?

to test it, park on a steep hill facing uphill.. shut off the car, put it in first and release the handbrake. if it starts rolling backward you have a clutch slip problem.

[Draven]

Generally a slipping clutch will mean the car very happily gets to redline, you just have less power going to the wheels during the high area of your torque curve due to slippage.

A sudden drop in power at high RPM is generally one of 2 things: fuel or spark. If it's fuel, it will happen primarily under heavy load only. If it's spark, it will be entirely RPM dependant. So if you have the same problem whether you're at half throttle or full noise, I'd be checking your sparks, dizzy, and ignition leads (in that order).
Otherwise, a fuel filter change followed by an injector clean might be on the cards (in that order again). There are also other fuelling options (fuel pump dying etc), but those will be your most common problems.

My bet is on spark issues

[CrUZida]

Clogged exhaust will do the same too.

[phrostbyte]

Sounds like a definate strike of a reluctantly releasing TVIS (Toyota Variable Intake System). I'm pretty sure 3S-GE's had them too. Basically TVIS is meant to close off half of each intake port until you get up to a certain rev range (usually around half way to redline, on a 4AG its 4200RPM), then it opens the rest of the airflow area. It's purpose is to create a greater vacuum effect and give more low down torque, then open later to allow the rest of the air the engine needs at higher RPM.

This is a photo of my 4AGE's TVIS squeezer plate. Notice the 4 butterflys.


With a permanently closed TVIS, at around 5000-5500RPM, the engine just can't get the amount of air it requires and the fuel ratio richens up, then the o2 sensor senses that and gives it less fuel, therefore, less air, less fuel, the engine would run as if you were only slightly pushing the accelerator.

Could be either the TVIS VSV is clogged and isnt releasing the vacuum, or your TVIS butterflies have become caked with carbon from reverse compression (the times you run your starter and the engine doesn't crank over properly, leaving the intake valves open and releasing the exhaust into your intake plenum) and gotten jammed shut, or in a very unlikely case, your ECU is being stupid and won't open them for some strange reason.

Hope this helps,
Kev.

[ViPeR_NiPPleX]

With a permanently closed TVIS, at around 5000-5500RPM, the engine just can't get the amount of air it requires and the fuel ratio richens up, then the o2 sensor senses that and gives it less fuel, therefore, less air, less fuel, the engine would run as if you were only slightly pushing the accelerator.

The o2 sensor will only be looked at by the ecu when its at partial throttle/cruising conditions.... Where as id expect someone at WOT to be trying to get upto those revs... however its likely it will still richen up if there is the restriction when there shouldn't be.

[phrostbyte]

Ahh OK, but yeah as you say, even so, with the restriction there it would richen up and not deliver as much power.

Kev.

[sideshow]

maybe yr tacho is wrong

put it in neutral and rev it to 7000

not a good thing to do but its one way to see if the engine will rev easily to that mark

if it does then u have a restriction somewhere thats stoppin it rev to 7000 under load

[CrUZida]

While your 'permanently closed TVIS' theory has merit, its physically impossible.

Have as look at the plate, they are always OPEN, and need vacuum to close.
So if the system malfunctions, they will lock open.
(this is assuming sometihng wierd hasn't happened and has locked the TVIS closed).


FYI, any car that runs an AFM will not richen up if the TVIS was locked closed.
The ecu will only give the fuel for the amount of air going into the motor.



Enjoy working this out.
Its either poor fuel, poor spark, or poor airflow.

[Simple]

Damn now I have alot to check this weekend!

thanks though, very helpful