1JZGTE revving up & down to 2500RPM on startup

[wilbo666]

[LIST][*]the ISCV resets itself when you turn the car off (it should go tick-tick-tick) Nope. ECU isn't controlling ISCV at all (as well as not giving ANY CEL codes/notifications)

Well there is the first thing to check.

Check continuity of the ISCV wires back to the ECU from the ISCV plug! Also measure the resistance of the windings from the ECU plug...

• the throttle plate is 100% closed, and the IDL contact on the TPS works only when it should This I havn't done, I'm not sure how.. will just leave it for the autoeleccy

It is simple, simply measure that the ECU pin IDL connects to ground when the throttle is closed, and disconnects (High resistance) to ground when the throttle is just opened.


Cheers
Wilbo

[Jabtronic]

Checked resistance.. heres my results

VTA1-E2 0.69k Closed, 3.5k Fully Open (gradiual resistance)
IDL-E2 0k Closed, No contiuity once Open.

Pin1 5V, Pin 3 12V with IG on.

Edit: I took the throttlebody off to check the resistance. Put it back on, engine started first go but revved up to 2.5k. So i turned it off, took 30 seconds to partially block the iscv pipe, then when i tried to start it again it wouldn't. Thats how random the problem is.

[CrUZida]

Have you made sure the throttle plate is 100% closed?
Although with the randomness of the problem, I wouldn't expect it to be the problem.

[CrUZida]

Oh, I should point out that I've had a 7MGTE do the wierd idle hunting thing before, but it only happens after I've tried to start the car with a flat battery, and managed to start it with a jump start. Once its started it will hunt for about 5mins until the battery has some charge (at least thats my guess on whats going on).

I have no idea what causes this, or why the engine does it, but its consistant (had it happen on a couple of different 7Ms).

Maybe faulty alternator or dying battery?
Unlikely, but worth a thought.

[triptek]

I had a similar problem with my jza70 1jz, mine would only do it when it was cruising at about 1500rpm. All of a sudden it would start revving up and down very quickly, up to about 2300-2400rpm. After changing a few bits ie: iscv/ecu the problem was still there. So i checked the tps next. I checked all the specs and it was ever so slightly out. So i adjusted the tps while the car was running in one direction and it started hunting even worse, would do it just above idle. I finally got it adjusted to the right specs in the tech manual and the problem went away.

[JZX083]

Hey Guys,
On the JZA70 ECU isn't there a plug connected to a few wires coming out of the ECU. From memory there is a blue and brown that have something to do with the Idle???? I think they are labelled IDL2 or something similar??? Just a thought Maybe this plug is not connected????

[Jabtronic]

Yeah I'm not sure which plug you're talking about, so I'd guess if there is one it's not connected on my 1JZ (because I havn't noticed any plug like you've described).

Here's the JZA70 wiring diagram

[JZX083]

Yeah plug V in that wiring diagram mate, VTA2 and IDL2 that go to the TPS im pretty sure they need to be connected!!!

[CrUZida]

Those with the '2' are for the traction control TPS.
Not needed or used.

[JZX083]

Looking at that wiring diagram they go to the one throttle position sensor along with IDL and VTA. The normal tps is a four wire plug. Isn't there a second TPS for the TRC???

[CrUZida]

Yes, there is, hence, ignore it.

[JZX083]

So your saying the Throttle position sensor only needs pin 2 and 3 connected to work properly. So where does the earth come from for the voltage reference??

[Hengsta]

Im having the exact same problem with the rev hunting thing but ONLY with my Blitz ECU . When i go to plug my normal M/T ECU in, the problem has gone (been driving around with that in there now). Will give it another try to see if it still does it, when i get my car back next week.

Anyone have any ideas what the problem could be? something in the ECU stuffed? plugs? anything?

Just dont want to waste a good ECU.

[CrUZida]

So your saying the Throttle position sensor only needs pin 2 and 3 connected to work properly. So where does the earth come from for the voltage reference??

No, I'm saying anything with the 2 (ie IDL2, VTA2) are for the traction control TPS, and can be ignored (unless of course you have working TRC)

[Jabtronic]

Ok guys, autoelectrician came around today and we found the problem.

The rev hunting was simply a stuffed A/T ECU, tried it in my mates car and it did the same thing. I think it mustve happened when my alternator died and drained the battery on a 1hour drive back from the track a while ago.

Annd.. The reason the car wasn't starting was because I'd hooked my HKS fuel cut defender (which splices into map signal wire) up to ACC power, when it should have been powered with the ECU IGN/ON power. So when the engine was being cranked the map voltage was getting cut out which is why it fired up initially then power dropped and it wouldn't fire after. Simple thing that was easily overlooked..

I can't believe I never figured it out all this time.. it wasn't until the autoelectrician started checking the MAP signal voltage then I thought hang on.. I've powered the FCD through my custom fusebox which uses ACC to switch the power through a relay. Not sure why sometimes it started and ran fine though.. I guess when the engine was off long enough the battery had a little more charge upon firing, and maybe I didn't hold the starter on too long..? Ah well, glad it's up and running again.

Thanks for the help guys