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jzx100 1jz vvti g4x pnp - can somebody please help me make sense of this

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Hey guys fairly new to actually getting involved on the laptop having come from a more hands on mechanical background prior,

I have purchased a jzx100 mark 2 with a link pnp ecu, the car will break up under boost what looks and feele like beyond half a bar roughly dependant on gear, a little higher if loading it up in a higher than necessary gear,

It runs yaris coils and 1000cc injectors on 98 octane aussie fuel,

I have checked over all of the coils and put freshly gapped bkr7e plugs in and tried my luck at .024 but still the car will not make any smooth power and continues to break up, so today I put the laptop on the car and have ran a couple of short logs down to the service station and back for some fresh fuel.

The previous owner had been having these issues for some time, I do believe that is why the yaris coils were swapped on in the first place, presumably to try alleviate any oem spark issues that were present, although with good condition coils and leads I've never had any issue running 21-22 psi as this car does so I don't think there was ever an issue in the coil area, just as a hope and dream fix I guess.

At this stage I'm thinking it could be on the tuning side of things but before I take it to someone with a bit more knowhow I figured I'd see if i could at least try and gain back some drivability.

I'll also load the map which I believe was tuned somewhere in Sydney where the car came from, does not look the nicest but again over Christmas it will have to suffice.

Thanks heaps guys any help is appreciated as I'm scratching my head at this one.




First thing I saw is that it runs super lean. A misfire can cause a lean condition, but right now I think you have a fuel delivery issue. I would check on the fuel system first to make sure you have the correct pressure and nothing is clogged.

I can't see the logs, but some general comments.

As Francis said, a mis-fire will allow oxygen to pass through to the lambda, causing a "lean" reading - sometimes people, or ECUs, will add fuel which can make a rich mis-fire much worse.

He's also right in suggesting you check over the fueling side - making sure the fuel system is able to handle the fuel flow is one of the basic points, biggies here being filters are clear and clean, pump is getting the voltage and amps it needs, injectors are cleaned (some have internal mesh filters that can also block) and tested.

Oh, check the fuel regulator is referencing the manifold pressure - there should be a line from the regulator to the manifold, and if this is damaged or missing the pressure delta will take a dive.

As a general guide, a lean misfire will have a sharper crack, a rich misfire will have more of a muffled bang.

Spark plugs should still be a "go to" when there is a problem, as they can tell you a lot. There are numerous guides on-line, but some of these are -

Any difference in appearance between cylinders?

Is there a dry, black, sooty look to one or more - an indication of a mis-fire.

Is there a shiny black appearance to any - a sign of oil control issues. It's also a common cause of deposits building up.

What colouration of the earth strap is there - this can indicate the combustion heat and can aid timing settings.

Is there any speckling on the insulator, or shiny spots - this may indicate a too hot (IIRC) plug.


I have similar sentiments as Frank, there appears to be a fuel supply issue. Assuming the lambda is working correctly, even in areas under load where it is not misfiring you are a long way off target, well above stoich and probably too lean to support proper combustion (you can tell where it is misfiring as the Engine speed ROC parameter gets erratic).

Also, not related to your issue but just an FYI, your accel enrichment setup is very odd so not working at all. I will suggest some settings later if I remember.

Thanks heaps for your suggestions guys I will go through the fuel system tomorrow and attempt further diagnosis.

Would there be chance for the lambda sensor to be faulty? As it did appear in the event log an 6 low voltage and lamba 1 sensor error of some kind from memory, I'll have another look first thing tomorrow and see what I can make of it.

And oh thanks another thing to look at, once I've sorted the issues I will take it to a local tuner and try have it sorted properly.

Also when I first looked earlier base fuel pressure on the fpr800 showed 38psi with the vacuum line connected, the injectors were said to be new sonic items that were flow tested, bpp rail etc. I would like to think those parts are good and the 460 pump seems to be doing its job which was also said to be fairly new. I will check maybe fuel filter etc and take apart the system and check for blockages.

I will update tomorrow any findings!

Yeah I noticed the historical AN Volt 6 error and related fault code in the log also, but in the actual log the voltage does not go outside of the normal range. That doesnt mean it is accurate though, AEM controllers are not renowned for their long sensor life. It is showing close to target at idle though and only shows lean under load so that hints it is not a sensor issue.

It would be best to put a fuel pressure sensor on it to confirm that there is a fuel pressure issue first rather than waste time looking for blockages. It could be a pump voltage issue or cavitation on the suction side or a hundred other things.

Thanks Adam much appreciated that's a valuable addition and as you say will save time chasing it elsewhere. Will update as soon as I have more info!

For the lambda sensor error, the 12:11:01 log shows that AN Volt 6 briefly goes at 0.02v when the sensor is heating up which is a normal behavior for some external controler like the AEM X-Serie UEGO.

I would advise you just set the AN Volt 6 "Error low" at 0.00v as it will just keep throwing that error code for that reason.

I'm also gonna point out that you should be careful when driving your car while the problem is still present. Hitting those boost level with a lean condition could damage your engine permanently.

Thanks Frank I'll change the error low value to 0.00 for this particular sensor.

And regards to driving I don't plan on taking it back out until I have some hopes of resolution, that was only to get info for the log as I had no idea what I was battling while driving.

I will investigate further this morning and report back any findings. Thanks guys.

All JZ cars are known to get very big voltage drop at fuel pump terminals as the time goes by. I would check the voltage there first.

So looking over things this morning,

Everything is fresh from tank to rail and the 12v relayed mod for the 8-12v system is installed, fpr shows good idle pressure, haven't got a fuel pressure sensor installed as yet as I will need a little time, but at this stage things are I guess pointing toward the fuel pump being no good even though its a pretty new unit, I will try and get some testing done today and see what's happening.

So I tested voltage at the pump was getting good voltage across the terminal 13.5v but I took the pump out and the sock was rusty and full of crap so I swapped in another walbro 460 and fresh sock and cleaned up what I could, lines are clog free, reassembled and have found some improvement, I will post the new log, still fluctuating afrs but the map honestly does not look any good. I got a video of the fpr and the pressure is steady,

Much less breakup while driving, but it seems to have a lot of target area where it wants to be around 0.95 lambda and then finally comes towards target of .8 or so. Looking at the log though it's still far from smooth.. I wonder where to next, as there is an improvement 100%, but unsure where I go next besides taking to someone to tune properly..

Let me know any thoughts!


How is the idle quality? Because at the beggining of the log and at the end, you're idling at 1.10-1.15 lambda so it wouldn't be idling super crisp.

Make a log at idle from cold to hot without touching the throttle. In one of your previous log, it looks like it was "okay-ish" at the start and was leaning over time. This is an indication that your sock could be getting clogged over time. In my experience, even if you clean the fuel pump sock, it won't be enough. You need to empty the fuel tank and clean the inside because it will clog back in no time. Of course, I haven't seen the inside of your tank but we had to clean 3 fuel tank last year in S13 chassis.

Hey Frank, yeah the inside of the tank is not perfect by any means from what i could see, it may come to it that I need to empty and remove the tank entirely, I am hoping it won't come to that but we will see. I will get another log shortly and throw it up.


There you go Frank, cold to operating temp, warm up enrichment working and then drops back to a touch over 1 lambda. Hope that gives some insight, it's been a lot of grief, if I have no luck by the weekend I'll have some help hopefully in a shop and on a roller.

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