2JZ NA-T Walbro fuel pump setup

Hi, I am doing my very first tune now and I think I might got the fuel pump setup wrong. I did an NA-T conversion on my non VVTi 2JZ GE, stock engine, for now still with a distributor ignition, stock everything except the turbo, IAT, MAP and wideband sensors, ECU (Supralink from Link ECU) and the fuel pump. Now I dont want to hit any excessive hp (as many builds tend to hit at least 500+hp), just want a nice road driveable Supra. I followed your Practical standalone tuning course and I got the engine up and running and now I am trying to tune the idle properly. And now comes the problem I encountered. On the same setup (idle base position, fuel and ignition tables) it sometimes acts differently. The vacuum is steady at about -60 kPa, so I am guessing there are no vacuum leaks, I can get it to idle from 1300 to 1000rpm (with startup offset active and decaying) and then at the 1000rpm it is nice and stable (basically as it was before I rebuild it). But this is the ideal state. Sometimes when I start the engine up it goes up to 900 and then falls back down to 600rpm+- and I need to step on the gas pedal to keep the engine from stalling. Other times, it goes staright up to 2000 and then drops to +-1600 rpm and I am unable to lower it other than turn the engine off and on again. All while I dont touch any of the settings I mentioned. I figured that the fuel amount delivered to the engine must be acting up to cause this issue and because I switched the stock fuel pump to Walbro ITP216 I either wired it wrong (I just wired it to the same wires in the tank that operated the stock one) or had it setup wrong. I can send you my tune as it wont allow me to upload it here and I would appreciate any help on how to solve this and move forward. The one thing I have done when I set it all up from the Supra base map from Link was that I switched the Active state from Low to High. I thought that the pump was not supposed to be running before the engine does, except for the prime time, which with the initial "Low" setting it did. I know there is a fuel pump ECU that operates the pump with PWM, but as the engine doesnt have a fuel pressure sensor, I dont know what the pressure acctualy is when the engine is running. I saw some people wiring their aftermarket pumps straight to the ECU and bypassing the fuel pump ECU. And forgive me being a noob with little to none knowledge and practical skills, as I mentioned I do this for the first time :) Thanks for any feedback.

Michael,

Idle control valve issues are extremely common on 2J often requiring replacing old units, but ruling out a fuel pressure issue is a great idea.

The best way to check that, and have data you can use during tuning and for safety measures, is to add a quality fuel pressure sensor. If fuel pressure is appropriate and consistent for a given manifold pressure, then you know you can look elsewhere for your idle concern.

Hello Mike,

thank you for your reply. I would like to come back to the topic as I was tooling around with some stuff but I dont think I got it resolved yet. I installed the fuel pressure sensor and I get around 310kPA on idle, stable per given manifold pressure. This I believe rules out the fuel pump working incorrectly or being setup wrong. I checked the runtime value for idle possition when adjusting it and it reads what I enter in the table, so idle control valve problem seems off to me as well (if it was erratic or changed per given manifold pressure etc. I would understand, but it is stable and the same that I input).

Now because of the fact, that I can get it to idle smoothly when the engine is running in its normal operating temperature of 80 degrees C on open loop, and the "jumps" and sudden changes in rpm occur only within tens of seconds after the startup, I suspect the problem might be in post start enrichment, warmup enrichment and startup offset tables. I tried to change the numbers in these and it does affect it, but I cant seem to get it right anytime. After the idle status changes from post start to open loop, it becomes steady again, but before it does, I cant get it to reach my desired rpm target. I can disable tha warm up enrichment and tune the idle base position without the enrchiment affecting it, but it feels wrong doing it like this.

Could you maybe direct me in the way I should try to move in to help me get a grip of this?

Any feedback would be much appreciated, thanks.

While the fuelling and ignition timing will affect your idle speed and quality, I doubt it's going to give you the problem you're encountering. The 2JZ uses a 6 wire stepper motor for idle speed control and these have no position feedback so the ECU doesn't actually know how many steps open the valve is. Usually how this works is that the ECU will fully close the valve and then step it open to the target position and then work from there. I'm suspecting that the stepper reset isn't occurring as expected or there is a physical issue with the stepper motor which is not uncommon.

I'd start by checking how the stepper reset is functioning. It can be set to occur at key on or key off. Key on is problematic because if you put the key in and immediately turn it to the crank position the stepper doesn't have time to do the reset and will usually idle low/stall until the stepper opens. On the other hand if you key the ECu to the on position, leave it for a second or two and then start it, the stepper should be in the correct position and it should idle properly. My preference is to do the reste on key off as it avoids the above issue, however the ECU needs a correctly setup power hold function. This should be fine since its a pnp ECU but thats where I'd be checking.

Hi Andre and thanks for your reply. I had it set to key OFF, I checked the runtime values and it does what I think it should do - go to fully closed and then open according to the set value (start offset + idle base position).

I played with basically all the enrichments, hold and decay times and now it firest up more quickly and gets to my target RPM without any erratic changes in the engine's speed (seems like the LINK base map for Supra had it set up for a completely different engine setup, than what I have). However it still doesn't satisfy me as to how the engine runs before it warms up. The idle speed is constant to my targets now throughout the warm up process, I set the enrichment so that the lambda is what my target is, but it feels like the engine makes vibrations before it warms up completely. Now it runs on closed loop and with idle ignition control on (I also played with these two setups a bit).

What I suspect now is wrong are the target RPM at different ECTs. I managed to find the good target at 80 deg C and (I think) thats why it opperates smoothly. What do you think I could aim for to correct this?

Thanks!