1jz-gte major power taper beyond 5000rpm

[urantia]

noticed the power tapered off quite abit after 5,000rpm, seemed like it may of been leaning out or breathing restricted.

As an example today, i was in 2nd gear and let it rev out to 7000rpm. The needle shoots up to 5000rpm quickly then becomes very slow to reach 6000 and 7000rpm. (probably 4-5seconds to go from 5000-7000rpm) And no thrust whatsoever.

Without having drivin another 1jz it's hard to guage how it should be, but it it's surely not right. Anybody tell me how there 1jz revs out, (not that i reakon it's good to rev out to 7000rpm) but i need to know how it should be.

I am not pulling any codes, i installed a new fuel pump and filter which helped with other issues. Might be time for injectors to be cleaned but i'd of expected a code if it were leaning out like that.

[Buttocks]

A 1jz should rev out nicely all the way to its redline, without a major drop off in power, maybe your bleeding off boost as you go over 5000. Have you got a boost gauge installed, whats it showing??
Actually now that i read your post again yes its sounds more than just bleeding off boost

[urantia]

I have the 1jz-gte boost sender unit hooked up to an ma70 digital dash turbo guage. You raise a good question and the stock bov is dented and could be stuffed. Need to get a boost guage and check this by the sounds of it.

Feels like a ton of timing is bieng pulled, but no codes from the ECU.

When the ECU has been reset the power is back for abit and then it seems to quickly adjust back to it's gutless state.

[Buttocks]

Don't have a friend with a spare computer you can swap around to see if the same thing happens

[urantia]

no unfortunatly, as i've heard 1jz ecu's of around this age start playing up (or any ECU for that matter due to the capicitors leaking)

I'm the only one with a 1ja motor i know of in tas -
I'll have to get ahold of a boost guage and check what my boost is doing i think your onto something with that, as i don;t have a very accurate way of measuring it with the stock guage.

Just strange i am not getting a code, the ecu must think it's acceptably safe that it won't bother with a code.

[Buttocks]

Its only a small cost outlay for a Gauge and you really should have one if you think about adjusting the boost, as the factory digital boost gauge isn't really worth a pinch of ____

[urantia]

Yep thats what i'll do next. But i still don't know why reseting the ECU restores the power (at least for a few runs). *Scratches head*

[acmtt]

I doubt its boost related.

It sounds like you are not getting the spark, check that the igniter and wiring from there to the coil packs is good. Check the connections to the coils etc. check coil packs etc.

A mate had a similar problem.

[2JZR31]

Close down the plug gaps a to 0.8mm

[urantia]

yes thats a possibilty, i am still using the spark plugs form the half cut, they looked good and i check and adjusted there gap to .8mm. The coiipacks looked good no obvious cracks but they could be delivering a weak spark up in that rpm range. Would the ECU normally spit a code out if this was the case?

[slide86]

how bout knock sensor? pulling timing out of it?

what fuel are you using. if you reset the computer , it may reset knock values, then once it boosts up a few times it deteects knock and holds that value.

[urantia]

Yeah i thought about that too, but i would of expected an abnormal rich/lean fuel condition code to pop up. But maybe not

Since i'm in tas i can only get normal premium, no 98 octane BP etc -
I suspect your right in that the ECU is picking up something and keeping the motor safe. But i wouldn't expect such a difference from using normal premium.

[Rossco]

mines was doing the same with the stock twins and wouldnt make much more boost then 13psi

ended up being the cat was collapsed
might be an idea to check urs out, if u have one

ROSs

[-GT-]

I don't think its spark, you didn't mention its rough, hesitating or missing. Its not plugs, i'd be pretty suprised if all six plugs were causing it to miss equally, and if not you'd notice 1 or 2 cylinders not firing up past 5k rpm. But i AM suprised you're using the plugs out of the halfcut. Go spend $25 and get new plugs.

I agree with it possibly being knock sensing. You said yourself it felt like a heap of timing being pulled out, and i don't think the computer spits codes for knock sensed. Remember, this ecu is tuned for 100ron, best we've got is 98 (i don't count that shell 100 stuff), and you're using what, 95 octane? I'd say there's a pretty bloody good chance its pinging its nuts off under revs + boost, especially if you're running higher than stock boost.

[chris davey]

Whack some octane booster in with your 95 oct and reset the ecu and see how that goes.

3 octane points is actually quite a big difference