Odd "spluttering" at high revs (1g-gte...)

[Hydra]

Hi!

My 1G-GTE is spluttering at high revs, while on boost. Seems to happen when boost hits about 12psi or so. I've checked that the nuts that hold the turbos to the manifolds are there, and tight, which they are. I've checked all the intake pipework, which all appears to be sealed up nicely.

The odd thing I have noticed is that it wont always happen. If the engine is cold, hasn't been taken above say, 3000rpm, and then I give it a boot full it'll rev cleanly to redline reaching full boost too. Then a little while later it'll start spluttering as it revs, and there is quite a noticable amount of smoke from the back (running rich - fuel smoke). It's as if the engine is just dumping fuel when the revs get a little bit high with more boost.

The ECU appears to be spitting back error code 12 - this suggests something wrong with the ignition circuit, specifically the distributor. I've checked the wiring between the distributor and ecu which seems ok from what I can tell.

I am not sure if it's the distributor or AFM or something else at this stage - no way to test this either as I don't have any spares of the affected parts

Any suggestions?

[-GT-]

I'd say it sounds like your spark is breaking down, check/renew plugs, leads, coil. It sounds like perhaps the coil is struggling when it gets hot, but leads may also be the culprit. How old are those bits?

[Hydra]

New plugs (sorry, should have mentioned that!), lead from coil to distributor is new, but the original leads from the dist to spark plugs. I will try and shield the coil somehow, hopefully that will help if it's heat.

I'm not sure what I can do about the leads, other than buying some of those generic ones that supercheap etc sell, and just throwing them on. I may as well get another set of plugs I guess while I am there! I guess it is possible they have fouled too.

The coil is really the only thing I can't easily replace - unless I can find another one

Thanks! Any other suggestions will be appreciated of course!

[-GT-]

So the coil is mounted on the firewall or somewhere, away from the engine? Less likely to be heat affected but they still can die, it may be on the way out. I'd definately be changing the leads dizzy -> plugs if they're old, good chance they're the problem. If the plugs are brand new you shouldn't need to replace them. You didn't change heat range or anything with the new plugs?

[Hydra]

Nope - they are the correct plugs, can't remember the model number off the top of my head.

If all else fails I will just have to track down a replacement coil/ignitor unit

[Hydra]

The coil is mounted next to the brake master cylinder... which means it might be subject to a little bit more heat since that is the side the turbos are on

[Hydra]

Ok, the new leads didn't help, it's still happening

I'm going to try re-adjusting the timing. I know for a fact that the crank pulley is several degrees out but i've marked TDC on the crank pully so I don't imagine it's too far out. I have had it set to 10 degrees or thereabouts. While I'm at it I'll reset the ECU diagnostic codes to see if 12 comes up again. After that, I suppose I'll start looking for a new ignitor/coil.

The one thing I noticed while I had the timing light on the engine today, is that it almost seems to drop into static timing mode while idling, intermittently. I don't know if this is normal or not - the idle does jump between 1000rpm and 500rpm, or rather sits at either.

[Gttwinturbomk3]

1ggte engines with out a lot of mods dont paticularly like being revved out to much, as they dont make any power up above those sorts of revs or go any quicker! So its just a waste of time pinging it out more than that anyway.

[{Mr Crabs}]

I know exactley what you are talking about my stock 1G (gen 2) seems to do the same thing.I have had it on the dyno a few times, and you can see that ,but not on every run.

The bloke who owns the dyno said that my stock ecu was like a large lump of shit holding me back . After all this is 1986 1/2 lol

Cheers Case

[Hydra]

Yeh the ECU is shit

Mine used to rev out fine, the EBC would hold 15psi to redline nicely. Now it wont with this sputtering thing.

[3BarSuperstar]

What is the plug gap set to? Try closing the gap down to .8mm or .7mm to see if it stops the missfire.

[Hydra]

Good thinking - hopefully will have a chance to try this today.

I think the plug gap is supposed to be about 0.8mm for the 1G-GTE - I suspect the plugs I am using are set to 1.1mm standard.

[Hydra]

Set the plug gaps, didn't help.

Quickly running out of ideas! Maybe it's a sign that I should upgrade to a JZA80

[3BarSuperstar]

Does the 1G have a rotor button with contacts on two different levels? I had a 1G once that would't run on all cylinders and it turned out to be the rotor button. It had little resistors in the rotor button and they were burnt out. Ground them out and put wire across to test it and it ran ok. Don't know if that will be your problem but it's a strange one i had. Have you tried a coil or ignition module. Engine earths??

[The Real Roadrunner]

could it be that the timing is to far advanced and the engine is pinging thus causing ignition brakedown and loss of power? have seen it on a couple of occasions, not long after followed by a dead engine.

cheers
linden