1jz advice/possible overheating

**naten** · 22-09-2006, 12:54 AM

hey guys,

Just wanna run a few things past you guys and see if i can sort a few things out.

When i last pulled the plugs (BKR6E's) outta my 1jz they were white tipped and the insulator was white to meaning its been running hot. What im wondering is do i simply get the next heat range up or will that just mask a problem i have with cooling?

I have (I believe) a 3 core radiator, the temp guage doesnt move above half unless im stopped for ages or its hot when i turn her off. So im thinking its probably not that causing it.

It normally starts missing when its been idling for a bit to and the idle moves up and down approx 200rpm. Im not sure if this would be caused by the plugs or something else? It does not miss and has never missed when off idle or boosting.

Ive checked for air leaks to no avail. I drop the oil (penrite hpr15 10w-60w) and change the plugs every 5000ish kms.

Im lead to believe most people use the bkr6e's in stock 1jz's and bkr7e's in modded 1jz's ? mine is stock minus 3" zorst which brings with it more boost (around 11-13psi). Am i simply running the wrong heat range?

The car seems to run ok (did a gtech run of 0-100 in 5.5 tonight darno what it should do) but does loose puff higher in the revs. 1st pulls hard to 7k 2nd seems to take long once it hits boost (3.5k to 7k). To be honest it used to feel quicker, especially the 'pull' in 2nd.

Anyone with a 1jz manual ma61 tell me if you boot it once your moving in 1st (say a soft launch) does it spin? Mine does not and my tyres arent the best (225 yoki A509's).

List of mods
stock 1jzgte jzz30 auto ecu
stock jza80 IC
stock Y pipe but 3" dump 3" cat 2.5" muff on the rear
3 core rad with thermo fan
basically a stock ma61 with a stock 1jzgte with a 3" zorst

I really appreciate anyone who can help me out with a bit of knowledge or experince with their own 1jz's

cheers
nathan

BTW this may not make sense cuz im piss tired

**Dangerous Dave** · 22-09-2006, 01:50 AM

I don't know much bout 1jz's, however this quote is out of my workshop manual in the spark plug section.

"Overheating. Electrodes have glazed appearance, core nose very white - few deposits. Fault: plug overheating. Check: plug value, ignition timing, fuel octane rating (too low) and fuel mixture (too weak). Discard plugs and cure fault immediately."

So definately don't get the next heat range up. If your not idling properly I would say you should be looking at the ignition timing and fuel mixture.

Hope you fix the problem.

Dave

**Vios-GT_07** · 22-09-2006, 02:43 AM

hi-octane fuel? fault codes?

when u say stopped for ages, typically engines can stay idle without issues for up to 20 mins++ (roughly), before the temp gauge will creep up..

try a few things like cleaning out your radiator, flush coolant from engine, new thermostat, any hose leaks etc..and if you test you temp sensors would be good.. test for BHG if possible (coffee coloured oil...? it's a long shot but yea.. just to be sure) and compression test as well.. could be one cylinder's lost compression, causing your lack of pull?

and from the sound of things, u're running lean, explains the plugs and temp.. so... brings us back to hi-octane fuel?

**naten** · 22-09-2006, 08:10 AM

i thought timing on a 1jz was completely looked after by the ecu/ignitor? hmmmm

i run BP ultimate all day every day, on the very odd occasion ill use lesser quailty if im out in the country with no 98 octane stuff around, ive never run octane boost or any other additives.

The time varys usually around 2-3mins i would say. Give it a rev and it revs fine.

was thinking maybe fuel pressure? im running the stock ma61 intank pump

**wilbo666** · 22-09-2006, 09:49 AM

Originally Posted by Vios-GT_07

when u say stopped for ages, typically engines can stay idle without issues for up to 20 mins++ (roughly), before the temp gauge will creep up..

Ever seen the front end of a MA61, not exactly a lot of cooling happening there....!

Anyway, when I've pulled my plugs in the past the have looked how you have described...I wouldn't be too worried about that. I don't think that it really sounds like you have a problem with cooling...

There is no way on earth I'd be running the stock MA61 pump tho. Go get a walbro they are quite cheap!

Cheers
Wilbo

**naten** · 22-09-2006, 06:41 PM

yea i know good for aero bad for cooling!

it never occured to me lack of fuel pressure could be an issue, go the old ma61 pump

hahah

any one got any ideas/advice

**thechuckster** · 22-09-2006, 09:13 PM

might pay to check that the aux-air valve is clean and functioning and not leaking.

**naten** · 23-09-2006, 12:36 AM

whats an aux-air valve? ive run over some diagramed pics of a 1jz and i cant see it (probably my shitty eyes)

**allencr** · 23-09-2006, 01:03 AM

Hot spark plugs, and hot cooling system are different & pretty seperate things.
Plug heat range, and/or lean from leak, low fuel pressure, dirty injectors, oxy sensor...........

**naten** · 28-09-2006, 10:47 PM

thanks your replies guys.

Ive pretty much fixed the dodgy idle/miss

Having the carbon canister connected to the plenum would cause it to miss, on saturday it got so bad i almost couldnt drive her. Let the hose suck from atmo runs ok, block it off runs perfect, put it on the carbon canister and it runs like a truck........biazzzzre.

Im going to wait until i replace the plugs next and see how they are doing.

**thechuckster** · 28-09-2006, 11:36 PM

Originally Posted by naten

Having the carbon canister connected to the plenum would cause it to miss, on saturday it got so bad i almost couldnt drive her. Let the hose suck from atmo runs ok, block it off runs perfect, put it on the carbon canister and it runs like a truck........biazzzzre..

either the one-way valve in the cannister is not working or you have the connections on the top the wrong way round.

aux-air valve = idle-control valve - thing bolted to plenum with lareg (6pin i think) connector.

**naten** · 29-09-2006, 12:41 AM

ah yes yes the ISCV or whatever the technical name is for it, im going to double check it tom night but the idle is ok and seems to be caused by the carbon canister.

Na its pretty straight forward i cant bugger that up

but yea its really odd.

If it was leaking then it should do the same as just pulling the hose off. If its blocked etc then it should just suck nothing.

**naten** · 29-09-2006, 12:43 AM

the only real odd thing my car does now is loose power when cruising at 120-130 for a period of time, its really quite odd, cruise at above 120 for a period of time (varies normally 5-20 mins) and it will loose power and ill have to slow down and wait for it to kick back in.

It doesnt hit a cut or turn off its all still running just nothing happens when you hit the pedal until you slow back down and off it goes again.

Thats the gremlin ill be chasing for a while me thinks

**urantia** · 29-09-2006, 04:31 PM

My 1jz is abit like that.

One thing i have wondered about is my thermostat, i probably look into things too far, but would having a 70C thermostat cuase issues? I ask becuase would the ECU go back into a rich mode when the coolant temp goes too cold? or change it's timing etc if the coolant is too cold?

the halfcut came with this thermostat and the bolts are rounded off and very farkin hard to get to, so i can't put the correct temp thermostat in for now.

Heaters are barely warm unless you give it a good caining. I can usually tear up a street sideways in second gear, but 3rd gear is very dissapointing as is 4th and 5th i aam lacking power forsure. (running a horrible low ratio 4.3:1 lsd)