1JZGTE revving up & down to 2500RPM on startup

[Jabtronic]

Allriiighty.. today I replaced the caps on my auto ECU and found it made no difference, the old caps had leaked though, same as on my manual ECU. (Btw xistant I assemble and wave-solder circuit boards for a living now so no probs there, got the right resistors )

Then I checked the wiring going to the ISCV, which was all good, both middle pins had 12V etc.. I noticed though that the CEL wasn't registering any codes when I bridged the TE1 and E1, so I decided to try my old manual ECU again and it started and idled fine, ISCV, CEL codes working again and everything.

WTF??? Something must be dodgy with the body plug going to the ECU, because that's the only thing that has stayed the same when I replaced the engine wiring loom (after having similar problems with the engine not starting on the manual ECU)

But anyway that was good enough for now, I mounted the ECU and chucked the glovebox back together as carefully as I could then started it again to make sure it was still running sweet.. I'll just renew my RACQ membership for now, in case it ever happens again and if it does I'll just get it towed to an autoelectrician.

Thanks for your help everyone

[xistant]

jab might need you in handy then if mine start to leak.

you got a eproom reader ?

[Jabtronic]

Not sure, I've never used one.


Back on topic, the problem has come back.. twice. The first time was on Friday, my mate came over and we tried his A/T ECU and it ran fine so I thought 'ok then', bought another ECU (M/T) yesterday and yay it was running again.. took it for a nice drive.

Then today.. I havn't touched anything since driving it last night.. I went to start it and it did the rev hunting again. Then I went to start it again 5 min later and it wouldn't start (would fire up then die)... I came back 20min later after borrowing a mates igniter and it started and was rev hunting again. (I then plugged my igniter back in and it was no different.)

Seems to be an electrical fault that is affecting the ECU operation.. when it revs up and down the ISCV obviously doesn't work (both power pins on it have 12V) and it doesn't show any error codes when I bridge TE1 and E1, I know it brings up codes when it's running properly though.
If I block the ISCV inlet partially it idles and revs fine.. but I don't want to leave it like that.

I've given up trying to find the problem now and have arranged for an auto electrician coming on Saturday morning to check it out.

[oldcorollas]

check and clean the pins on the plug? check none are slipping backwards etc etc

[Draven]

intermittant problem that arrives after an ECU move? I'm with OC - sounds like a loose/dirty conenction somewhere... specifically the ISCV wiring.

[Jabtronic]

What I did on my old wiring loom (I replaced engine loom 2 months ago) was pull every ECU pin out of the plug one by one and used another watchmakers screwdriver to push the contact back up so that they had a firm connection. I guess I could do this again with the new loom I'm running. I had the 'not starting' problem before and after I did it with the old loom though (and also before and after the wiring loom swap), which makes me believe it's not the plugs/pins.. maybe something on the cressida or the 1JZ instead.

I've briefly checked all the ISCV wires too to make sure they are securely in the plug but I'll check again.

[oldcorollas]

maybe when the problem occurs, pull out multi and check continuity, from ECU to end item, for each wire, and see what is loosing connection.

or.. for say, the ISCV wires.. get someone to wiggle the ECU plug and the ISCV plugs and see if you drop cont or not

go do some wiggling

[Secks]

sucks to say it, but the wiggle may now be the best bet, before the sparks shows up saturday. My original suggestion seems a lil off target now. lol. It may still work. Does not require an engine code to be cleared, but i dunno.

And mates wonder why i prefer my old wolf3d unit. :S

[Jabtronic]

I've tried wiggling the ecu plugs HEAPS of times over the last 2 YEARS.. that's how long the problem has been happening (the ISCV hunting is new though).. I've bought 3 ECU's now (remember I bought one from Japan too through you a while ago OC) and I even replaced the wiring loom hoping that would solve it, but after doing all this the problem is still there.. it basically can't be the plugs/pins on the 1JZ loom.. or the ECU because I've replaced them both.
Really I should have called an auto electrician months/years ago and maybe the car would have been on the road sooner.

But ah well, cheers for the suggestions anyway. I'll keep you all updated how it goes on Saturday

[Draven]

that sounds like a royal bitch of a problem... good luck with it!

[Secks]

if you find the problem, this thread will make somebody else very happy one day...

[CrUZida]

As someone earlier posted, the hunting happens when the revs get to about 2500, AND the TPS is in IDL mode.

ie, the ecu is unable to control the idle (via the ISCV) and cuts fuel when the revs get to 2500 and turns the fuel back on at 1500 (give or take).

You need to make sure that;

• the ISCV is working correctly (fit one from a working mates car)
• the ISCV is wired correctly (check for voltage and continuity to ECU)
• the ISCV resets itself when you turn the car off (it should go tick-tick-tick)
• the throttle plate is 100% closed, and the IDL contact on the TPS works only when it should
• there are no intake leaks between the throttle body and the head (with the exception of the ISCV and power steering idle up)
• the ECU is working correctly (swap with a mates one).

If you have done all that, are are 100% sure its none of the above, panic and/or cry.

[CrUZida]

Oh, I should point out, next time it happens unplug the TPS.
If the problem stops, start with my list above.

If the problem continues, look elsewhere.

[Jabtronic]

• the ISCV is working correctly (fit one from a working mates car) Checked, infact mate's working ISCV is still on my 1JZ
• the ISCV is wired correctly (check for voltage and continuity to ECU) Checked continuity on the four ISCV wires and the two 12V wires
• 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)
• 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
• there are no intake leaks between the throttle body and the head (with the exception of the ISCV and power steering idle up) Checked
• the ECU is working correctly (swap with a mates one). Checked

It's really got me stumped. Bad earth/short making ECU not operate properly perhaps? Like I said it's hit and miss whether the ECU works or not.. I've put the dash back in 3 times now after having the car running sweet.. only to come back the next day or whatever to find it doesn't want to start again.

BTW I'll try starting it with the TPS unplugged tomorrow arvo.

[CrUZida]

If you unplug the TPS the revs should just go up to 3000rpm or so and hold there.

Have you worked out why the ecu isn't controlling the ISCV?

If the TPS is in IDL, and its getting the right voltage, then it should.

http://www.cygnusx1.net/Supra/Librar...spx?S=FI&P=101
Look at the IDL - E2 continuity.