Nistune Forums

Matt,
I have noticed this since day 1 of installing nistune, basically REGARDLESS of engine temperature, when you start the car after turning it off, it will run VERY rich (mid to high 10 afr's) for about 30 seconds to a minute, and then it will slowly return back to normal and read what the fuel table tells it to read.

I have concluded that its a part in the ecu's code to warm up the catalysts, in which I do not have or care about. How can I make this stop doing this?

Ive messed with ALL the cold start settings and adjustments to no avail. thanks.

Potentially part of the Nissan ROM code which has been programmed in your board for the ECU part number that we stuck in there

If the original ECU didnt have this in then only solution might to be to grab the ROM from the original. I think I installed to NA ECU and put something like the 1988 SS VG30ET ROM in there

What ECU were you using (which was turbo) which didnt have this functionality in it. I would need to grab the ROM and can use that instead

Actually... from what I REMEMBER this problem (not really a problem... its a stock nissan thing which annoys me) was caused by all the ecu's that I have been using.
Im running the 86NA ECU with the 88SS ROM image, but even my 87T board was doing the same.

most of these ecus have an "afterstart enrichment" map, that is applied for a minute or so after startup, the amount does reduce with temperature, but it is applied at all engine temps after starting.

also some nissans vent the fuel pressure regulator to atmosphere for increase in fuel pressure to aid hot starting (usually over 90degC) to get rid of vapour locks in the injector rail.

only two things i can think of above.

Have you zero'd out all the warm up, enrichment tables and start the car?

My CA18DET does the same but does not have any entries for a start-up enrichment table just a Temp enrichment table that doesnt effect start-up

Ok this is starting to get annoying.

If I turn my car off regardless of temperature, it will run EXTREMELY rich which makes my idle very low and unstable (goes up and down) and will run like this for a allocated amount of minutes (more than 4 minutes) and then all of a sudden it will smoothen out and the AFR's will get leaner and leaner until finally it actually goes along with my fuel map. (it doesn't start reading the fuel table INSTANTLY, it will be a SMOOOTHHH transition and the wideband will slowly go from mid 10 AFR's to mid 14's in a smooth fashion)

When I say rich, im talking 10.0 AFR's (Mostly mid 10's AFR)...

I have Zero'd out ALL the cold start and warm start and ALL other enrichment maps and its still doing it.

It is very annoying and burns a lot of fuel for absolutely no reason...

What do I do now?

Matt!

Not leaking injectors or a faulty regulator is it? does it hold fuel pressure when you shut down?

Regulator is brand new with a built in gauge, holds pressure VERY well.

Car runs fine, its a Software issue or fix, no doubt about it.
Car runs flawless other than this.

Basically we have identified all the known 16 point maps in the R31/Z31 ECUs, so there are no other maps in this ECU that can be adjusted

Now you mentioned that this occured since installing Nistune but have also indicated that it is part of the factory ECUs code (which should have existed before installing the board with factory EPROM chip) - I'm a bit confused here

Nistune software only provides a mechanism to change the existing maps on top of what of factory code.

As such there is no software fix that can be implemented to change something which is factory ROM code implementation since all we do is allow retrieve/modificaiton of maps and report consult registers

Does fuel pressure remain constant from first starting to later when car runs ok?
Dunno bout the Z's but the VL's and VLT's have have valving to stop vacuum to reg after starting so as to increase pressure by 50kpa and the VLT even stores boost and applies this to the reg for even more.
Maybe try vac line direct from manifold to reg.

You mentioned before also that the problem was noticed only after installing the NIStune board

What ECU and other engine/injector etc setup details were you running at the time prior to this?

Fuel pump is not ECU controlled, I am controlling the Pump by a relay, and the fuel pressure regulator is not stock, it is aftermarket and there is a direct vacuum line controlling it, so nothing is adjusting these.
Fuel pressure is at 41psi AT ALL TIMES, regardless of engine temperature.


Matt, I have no idea if the ECU did this BEFORE I installed nistune, because I NEVER had a wideband, so I will never know.

I am certain though that it was there before (not 100% certain, but more of a guess , lol)

I guess it does this to warm up the catalytic converter, its just that it gets very annoying, because it makes my car miss from running so rich!


So I guess theres no fix to it?

Since the fuel pump is variable rate, should be like my R31 it is voltage control so it has a lower rate around idle. How come you are controlling it via relay?