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Initial Start - Idle issues

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I have a Datsun 180b SSS running an FJ20Turbo I have had the car for many years and rebuilt the engine on several occasions. I regularly works on these engines and have quite a bit of knowledge. I wire aftermarket ECU's and calibrate all sensors and program a basic tune for the car to idle and run and drive in other words prepped for DYNO. In my own build this time around I am having a lot of issues getting the car to idle. I have recently rewired the car with a Haltech NEXUS. end to end with all functions and sensors calibrated and working. The engine is built 2.2 stroker, bigger valves cams, valve seats, rod, pistons etc. everything you can do to an FJ with 2433 siemens injectors. I have run the engine to 715rwhp on the last build prior to engine failure. and this is a fresh build. like I said I have ran this engine in my car and other friends vehicles for many yrs without having this issue, its very easy engine to start. I use a custom home trigger which is dialled in and engine is set to 10deg

I was able to start the engine which was painful but did and am able to hold revs at about 2000rpm with throttle. but once throttle is removed it stalls. I have played with mixtures but nothing seems to make any difference. Timing is correct set to 10deg and checked with timing light but have also tried to adjust this but no result. it has DBW. PS car was running with this setup prior to engine failure. working ion Haltech Elite 1500. changes since car running last are bigger housing on rear for Turbo and changed coils from smart coils to R35 coils. Dwell settings set correctly so are injector deadtimes.

I can assure you that CAM timing is correct, checked . All coils are firing, I have since drained fuel systems checked all devices and cleaned all fuel filters, injectors are getting tested currently. once they return I will do a smoke test to ensure no air leaks have also changed sparks plugs. Having said that I believe I will still end up with the same result.

in one of my tests with injectors turned off and plugs removed to clear out cylinders of fuel as plugs were fouled at point. when the engine was cranking there seemed to be fuel still coming out for some time... hence why injectors are being tested. I think it is far fetched that all injectors leak though!

Also, I do notice EGT no.1 temp higher on cranking than rest. When running all is good though :S.

I hope I was able to describe my issue well enough but any help on this would be great!


Hello is the map reading stable and where you would expect it to be at the 2000 rpm mark? it should be around the 65 or higher kpa

but i think you are on the right track with smoke test and injector testing, just to understand what do you mean when adjusting the timing it had no effect? do you mean it did not help?

Regards Ross

Hi Ross,

Thanks for your response,

ok to elaborate more on the issue.

Map is -9PSI so yeah around 65kpa at 2000-2500rpm. I can stabilise the AFR too at that rpm. there were times where I can get it to 1600 rpm without stalling using throttle. but normally 2000-2500 to keep it running. It also hunts at times but this is overcome with more throttle. I can also reaffirm I have checked my settings over and over again in NEXUS but will do again just in case. Even though I have a kazillion sensors I am running a basic setup to start the car, with most unnecessary items turned off. I can also assure you the timing is correct for cams and ign.

Lets say I moved the timing 10-15deg in advance and retard to see behaviour and if it would hold idle which it did not. so I have gone back to 10deg BTDC.

There is an obvious change in the engine behaviour with the change of timing when running but not at idle. It still will stall.

Just really confusing... I hope its an injector issue as that all i can put it to as the rest of the fuel system has ben checked. the smoke test Im sure will pass.

I will get test results for injectors tomorrow hopefully it will help.

Sorry I forgot to add its not even starting atm lol

have you checked it is running on the latest firmware available?

Hi Ross,

I can tell you I updated the firmware just prior to trying to starting it. Im not quite sure if there is a newer version.

I will see if there is an update as I have had an issue with car starting with my previous Haltech Elite, when I updated it once, and then had to backdate the firmware and it worked.

I will check this also

Thank you

Ok I have some progress...

After having injectors checked and good 100% and smoke test passed several times. I checked all wiring and found there was a incorrect connection at the dbw. The interesting thing is nexus did not pick this up! I was still able to calibrate with the signal gnd swapped with tps1 out Anyways fixed wiring and also found that the r35 coil was quite tricky to ensure the rubber seal sits correctly hence the starting issue.

I got it started and since dbw was working correctly I was able to to somewhat stabilise the engine much much better. After a couple hours of trying to tune it I was still having issues trying to get it to idle. To be able to get any stability i need to advance the timing 15deg.

I have the ecu locked at 10 deg. This is checked also with timing light with someone holding steady revs at 1500-2000rpm. Tdc offset angle is 495deg to achieve 10btdc in locked status.

for me to get the engine to idle i need to adjust tdc offset to 480-485 Which takes the timing to 20-25 btdc. Which is not what the ecu is locked at.

It holds revs between 1500-2000 but as soon as I retard the timing it stalls. It also stalls when my fan kicks is. I do use 3000 cfm hi amp fan but this is not running through nexus, Only trigger. Even with idle up adjustment of 200 rpm when fan kicks in and it still stalls.

I can say I have never had this much issues starting an fj. Really confusing

Any ideas?


Once you lock the base timing to 10 deg and adjust the base offset to achieve 10 deg timing unlock it and store this setting don't adjust it again this is only used to match the ECU to the engine. the rest is to be done in the main ignition map, (I know you are aware of this but just putting it here for others to see)

the engine should then only need in the range of 10-20 deg of ignition to idle if it needs more then you may need to open the throttle plate more to achieve idle rpm this is done in the DBW idle table. ideally, the fan should be run through the fan so the ECU knows to open the throttle plate more to suit the electrical load, sometimes this can be up to 8 percent more throttle opening. if the mixtures are going lean of rich when electrical load is applied for the same load zone then the injector dead times may need to be adjusted to correct it.

i have a question what does the engine SOUND like does it sound retarded? or over advanced?

does it smell rich or lean? sometimes your ears can be the best tool to find these

have you rechecked the valve clearance ?

Hi Ross,

I have success! Big learning lesson

And no I dont mind the obvious being stated as sometimes we miss things and it helps.

I guess I was looking in the wrong area.

There are no leaks injectors are good and timing is all correct. The issue was some of dbw idle control settings. To achieve correct afr and idle on 10deg it seems the throttle was open way too much. I spent a few hours monitoring the engine behaviour to see what was getting it to sounds and work better.

Idle control dbw max ws set to 10% which is quite standard and like I said I have never had this much issues prior. But this needed to be reduced to 3%!!! And im not sure why. And feedback would be appreciated to get a better understanding why this difference is.

Looking at another vehicle I have recently set up same engine and ecu

FJ20 standard crank and valves auto trans

larger cam 268

FJ20 2.2 stroker and 1mm oversized valves manual rb25 dogbox

Smaller cam 272

Both have adjustable cam gears both run haltech nexus both have same plazmaman inlet & dbw

To achieve stability hes dbw max for idle control is set to 11% runs at 10% on idle ( which is what haltech say is typical 10-20%) I am on 3% to achieve stability with around 2.7% on idle. This seems a major difference.

Why am i using so much less air on idle to achieve stability? Larger valves? Cam setting? Stroke?

I can say I now have a stable idle at 1050rpm with no fluctuation when fan kicks in. It's the best is has ever ran.

Thanks again Ross

Can you educate me in why this difference throttle position at idle is so large. I understand there are differences in the engines cam valves etc. But is what im seeing correct?

what you are seeing is correct you must just have goos vacuum on your engine at idle, this will suck more air past the throttle plate than an engine with a lower vacuum, that's the only reason I can think of anyway!

Great work sorting it tho, well done

There are at least four other things that may be contributing to the variation in the apparent throttle blade variation, any or all of which may be occuring.

1/ Different sizes of throttle body.

2/ Difference in the closed 'seal' - the amount of leakage around the blade.

3/ The throttle body calibration isn't correct in the software

4/ There is a vacuum/air leak you aren't aware of

That said, around 3% is closer to what I'd expect for idle opening, and less wouldn't surprise me.

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