Another 1jz Problem !!

[nemesis86]

Hey people, i've been muckin around with my brothers 1j powerd mz20 for the last week trying to get it run properly 1 problem was the ecu as injector 3 and 5 were completly flooding the cylinders but that has now been corrected, i also put a new walbro pump in it assuming the pump was another problem also took all injectors out replaced them and put new seals on them now it runs on all 6 cylinders but it idles low, dies in the ass if u punch the throttle and get off it.

It also does this flactuaing thing for example i'll hold the revs at like 2000rpm and without moving the throttle it just drops and comes back up, drops and comes back up continuosly, does the same if i hold it around 3500 or 4000 rpm it will be running fine then all the sudden the revs drop without taking the foot off the pedal then the revs return to where you had ..... its like it cuts out then comes on cuts out and returns to where you had the revs at, its really strange??

Any Help guys would be muchly appreciated guys

Cheers fellaz,
Ivan.

[wilbo666]

Any ECU codes?

Cheers
Wilbo

[Smokey228]

Man i had a problem very similar to this one. But apparently the 1JZ Ecu 'Learns' the map and eventualy the problem for me went away... If i disconnect the isolation switch over night, the problem comes back...

However, make sure you have no vacuum leaks, there are little hoses on the motor that hide all over the place, the one that i missed for ages was next to the throttle body...

Apart from that, im not so sure but Sasha from Canak auto helped me out heaps as he works on 1jz's a fair bit...

Let us know how you go...
Cheers,
Jase

[wilbo666]

To pull the codes:

TE1 to E1 in the diag box, then a light bulb between +B and W.

For codes, this should be close:
http://mkiv.supras.org.nz/techo.htm#ENGINE_CODES

I suspect that your bros conversion prbly doesn't have the check engine light wired up...which is where the light bulb between +B and W comes in.

Cheers
Wilbo

[JP]

the rev dropping and returning is caused by the "fuel cut RPM" feature of the stock ECU.

[Kedderz]

or the iscv is broken or theres a vac leak causing it to hunt for idle.

all things to check!

[Norbie]

As mentioned on another forum, blocked ISCV and maladjusted TPS explains the symptoms as described.

[Officer Doofy]

It also does this flactuaing thing for example i'll hold the revs at like 2000rpm and without moving the throttle it just drops and comes back up, drops and comes back up continuosly, does the same if i hold it around 3500 or 4000 rpm it will be running fine then all the sudden the revs drop without taking the foot off the pedal then the revs return to where you had ..... its like it cuts out then comes on cuts out and returns to where you had the revs at, its really strange??


Ivan.

Mate one of my Ecu's had the exact symptoms. Also did it at idle, 2000rpm then drop then 2000rpm and so on. I knew it wasnt the ISCV as another ecu worked fine and i had recently cleaned it. Changed all the caps in the ecu and the prob went away.

Pull your ecu open and have a good look with a torch at the bottom of the caps and see if you can see any goo or shit, if your confident just change them anyway.

[Slim]

My car has a similar issue (1JZ-GTE)... Just to clarify, the problem you're describing is only a momentary drop in revs. ie: it's like it dies for a split second?

My engine will do that when it's warming up sometimes. It'll be somewhere between 1200-1800rpm then *bleh* drop in revs for a split second, then pick up... then 5-10sec later it'll do it again... and so on. Am i describing the issue that you guys have?

I might have to open up the ECU again to have a look. I had a brief look when i did the conversion about 9 months ago and the caps looks pretty much ok. But who knows how good they're actually working.

[nemesis86]

Thank you to all that contributed information it is all very much apprecitated.

I finally fixed the car last week and i beleive it was the ISCV and the TPS, took the ISCV totally apart ... as this was the second time i've cleaned it, I also cleaned the valve/plunger looking thing that sits in the manifold where the ISCV sits, then i cleaned the shit out of where the valve/plunger sits in the manifold. put it all back together and..... she ran a beauty except it wasnt holding idle so i stuffed around with the TPS and then she was perfect the 1j ran better than ever.

Once again thank you to all that contributed and to anyone that has a 1j.... get into that ISCV and clean the fuck out of it along with everything else that is affiliated with it... shit it makes a difference

CHEERS!!
Ivan.


Oh by the way i used carby clean to clean all components then i used WD40 to lube it all up

[woggin]

yea sounds like an ISCV problem....we disconnected it on my bros JZA70 to see what would happen, RPMs just fluctuate constantly......1000-2500rpm !!!