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RB25DET Neo S15, timing/tps/running issues

nichthen
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nichthen Rookie

nichthen

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Hey guys, having a little trouble getting my RB25DET neo S15 to run right. I believe it's a timing issue.

Info about the car.

JDM SpecR S15 with an R34 RB25DET Neo engine. Wiring professionally done. 

IACV and AAC Valves removed and blocked off. 
Brand new plugs gapped to .8mm 
No air leaks
Tried 2 AFM's
Plenty of good fuel plus good fuel pressure. 
Spitfire Coil packs tested, injectors tested. 
tps voltage @ 0.45
Stock ECU, Freddy forward facing plenum, Turbosmart FPR1200 with a Walbro 460 fuel pump, FMIC w/ 3" piping etc etc.

Following the FSM to set the timing by warming up the car, unplugging the TPS and setting the idle to around 600 - which i use the throttle body stopper Phillips head screw to do, hooking up the timing light to the blue loop wire on the coil pack harness (and also went straight onto #1 cylinder wiring too). With the timing light on the pulley marks, its jumping all over the place. I get it as close to 15 degrees as possible but when plugging in a laptop its jumping around terribly. 

When I plug the TPS back in the timing is reading 30+ degrees. The only way i can get the timing back to around 15* is if i completely turn the TPS one way giving the ecu an apparent 0.12v of power. 

The car idles okayish, sounds like a slight miss when idling, stalls when revved most times and instead of coming back down to the desired RPM it was idling at before it will just die. When i try to actually drive the car, it doesn't like to even rev with any sort of load on it at all, sputters and dies, laptop says its in the 30-40* timing range when it does have load on it, doesn't give much power to the wheels. 

Shouldn't the car still read 15 degrees when its idling with everything plugged in? What have i missed here.

So in a nutshell, car doesn't want to drive, and doesn't stick to its timing at all when a TPS is plugged in and adjusted to 0.45v.

 

any help would be appreciated.

GTSBoy Grand Master

GTSBoy

Posted
Posted

This is happening because you have removed the IACV.  The ECU is trying to raise the idle speed and not getting anywhere (because, dun dun dun, no IACV).  So it resorts to advancing the ignition.

Put the IACV back on, or change to an ECU that doesn't need it.

nichthen Rookie

nichthen

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Posted (edited)
5 minutes ago, GTSBoy said:

This is happening because you have removed the IACV.  The ECU is trying to raise the idle speed and not getting anywhere (because, dun dun dun, no IACV).  So it resorts to advancing the ignition.

 Put the IACV back on, or change to an ECU that doesn't need it.

 

____________________________________________________________________________________________________________

Shouldn't raising the idle manually by the phillps head screw on the t/b eliminate the ECU's need for more air? I asked many questions when i was installing the plenum if it would be okay to delete the IACV and all i got were positive answers stating that "all you'll need to do is get the car idling is slightly open throttle body to desired RPM, then set the TPS to 0.45v to fool the computer into thinking its closed."  

 

Edited by nichthen
GTSBoy Grand Master

GTSBoy

Posted
Posted

The stock idle speed is XXX rpm (let's say it's 650.  I can't remember off the top of my head, but it doesn't matter exactly what it is).  If the idle speed is lower than the target, the ECU will keep adding timing to try to get the speed up. If the idle speed is above the target, the ECU will wind the timing down to 5° (or possibly even 0°) to try to get it down.  And no matter how hard you try, you will never be able to set the screw so that the idle speed is always on the target, so the ECU is always going to be running unusual timing to keep the speed under control.  Hot weather, cold weather, air-con, etc, all are able to make the idle speed move by a couple of hundred rpm. That's why we have IACVs.

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted
1 hour ago, nichthen said:

 

I see you have 2 posts so I guess your many questions were not asked on this forum.  There is a huge wealth of info on RBs on this forum and if you read carefully you will, like I did,   learn heaps that you didn't know before.

GTSBoy Grand Master

GTSBoy

Posted
Posted
9 minutes ago, nichthen said:

Clean. and unsure how to check if it moves or not. It has 12v going to it.

It's a stepper motor.  If you unmount it from the plenum (and block the holes/pipes it was connected to) and leave it plugged into the ECU, then it will (should) follow the ECU's command to open and close. If you run the engine and set the idle real low, the ECU should try to open it up.  There should be little resistance to blowing through it.  If you set the idle very high, the ECU should close it right down and it should be quite difficult to blow through it.

nichthen Rookie

nichthen

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9 hours ago, GTSBoy said:

It's a stepper motor.  If you unmount it from the plenum (and block the holes/pipes it was connected to) and leave it plugged into the ECU, then it will (should) follow the ECU's command to open and close. If you run the engine and set the idle real low, the ECU should try to open it up.  There should be little resistance to blowing through it.  If you set the idle very high, the ECU should close it right down and it should be quite difficult to blow through it.

Replaced the ECU today and still have the same issues, whether the iacv works or not shouldn't determine the car running like absolute crap and sputtering when revved etc etc. 

 

Anybody have any other suggestions? Even better, does somebody want to make a little cash by coming and sorting it out in person? 

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

I'll have a look at it. But you don't say where the car is so if its not in Auckland you'll have to pay me to travel.

But seriously it could be a lot of things. Best to eliminate things one at a time rather than the scattergun approach. Test the IACV and make sure its working properly and then move on. Have you correctly installed the FPR? Have you checked the CAS?

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