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RB25DET S2 Injector voltage


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RB25DET S2 Injector voltage

need some serious help. car went in for a metal gasket job and ffp install. injector harness was extended, battery moved to the back. On the first day it started, the was a slight miss at idle. and when we hit 5k rpm, it hesitates and misfires, as you release the throttle , it idles like a impreza for a few seconds and then its back to normal.

Changed to bcpr7eix and another set of coil packs (wreckers), now the problem is at 6k rpm. taped coils up, applied dielectric grease.... if on 2nd gear at 6k rpm on boost it hesitates and misfires. IF on 3rd or 4th gear at 6k is just feels flat and empty...it just wont go past 6k and holds. you can feel like there is a slight miss-ish but not misfiring, i dont hold it too long that way worried im gonna blow something.

During this entire time, afr is at abt low 11's high 10's. timing up top has been set from 21 to 18 to 17 and stll doesnt help.

injector duty is at 65%.

MAF at abt 4.8v . the airflow load point in the map is at P15 (11k )

TPS been adjusted and this happens at any throttle Voltage it happens. i tried holding it at partial or WOT. so i doubt its the tps. at wot its 4.4v.

Batt Voltage reading 13.8~13.9

Im kind of lost and loosing hope here. Car was mint before the job. now it just doesnt want to run right.

Things ive checked are also for boost leaks, vacuum leaks, CAS timing (set at 15) crank and cam timing(all on correct markings). The car holds boost just fine, and at lower revs all the way to 5.8k it pulls hard. at 6k it just goes F*&&ed. makes no power whatsoever.

I even went to the extent of buying another set of bkr6 0.8mm to try it and its the same thing.

Car Spec :
RB25DET
Stock turbo
3"exh
fmic
walbro pump
fpr 3bar ( no vac)
stock coils
0.8bar boost
cometic 1.3mm metal gasket
power fc with fc edit
aem wideband

what do you guys think it is ? Wiring issue for the injector harness? battery moved to the back ? if it was injectors, i should be able to detect it on the log right? if it was fuel pump, shouldnt the afr be super lean before or when it happens? if it was maf the voltage should either be maxed out or suddenly drop? Could it be the coil pack harness? Please help. any suggestions or pointers will be great. any troubleshooting ideas . sorry for the lengthy post

When i checked voltage for the injectors, i noticed i was barely getting any voltage on the 12v wire, its only abt 0.3-0.5v...  but on the ground with key on engine off, im getting 12-13v.  is this normal? shoulldnt i be getting 12v on both sides with key on ?

 

Edited by Dev RB25
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5 hours ago, Dev RB25 said:


When i checked voltage for the injectors, i noticed i was barely getting any voltage on the 12v wire, its only abt 0.3-0.5v...  but on the ground with key on engine off, im getting 12-13v.  is this normal? shoulldnt i be getting 12v on both sides with key on ?

 

 

Are you sure you understand which side of the injector is power and which side is ground?  Hint, the injectors are not fed 12v from the ECU.

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Why does the FPR not have a vac connected? Not only do you not have a vacuum reference at idle but you've got no fuel pressure compensation under boost either. If it was tuned like that then expect to start over with the tune.

Edited by XR Pilot
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12 minutes ago, XR Pilot said:

Why does the FPR not have a vac connected? Not only do you not have a vacuum reference at idle but you've got no fuel pressure compensation under boost either. If it was tuned like that then expect to start over with the tune.

I'm guessing that the (no vac) statement was just to tell us what it is set to when disconnected.  Then I expect it is actually connected in use.

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Ah, that's what I get for skim reading on my phone.

The other thing that comes to mind is the symptoms described will happen with a rich misfire - depending on spark strength it can happen at mid-high 10 AFRs. If the OP is comfortable with FC Edit I'd suggest pulling mixtures back to mid 11s and see if the misfire goes away.

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7 hours ago, Dose Pipe Sutututu said:

Are there enough earth straps from the motor to chassis and also where your battery is, is the earth point nice and solid to the chassis?

 

yea we added more earth straps, and the connection is solid. the voltage of reading from rsm is at abt 13.9-14v . compare to before the battery was moved which was ard 13.4-13.5

 

5 hours ago, GTSBoy said:

 

Are you sure you understand which side of the injector is power and which side is ground?  Hint, the injectors are not fed 12v from the ECU.

ground is the grey wire. and the striped wires are supposidly 12v. i keep reading that people are getting 12v at this wire. the injecors are normally fed 12v from the ign relay ? ill appreciate your help and guidance rather then hints . From the sound of it youre sure that im not sure about something, so why not just teach me  rather then make this sort of comments. Im here to learn. If i  was so smart and a know it all i wont bother asking.

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5 hours ago, XR Pilot said:

Ah, that's what I get for skim reading on my phone.

The other thing that comes to mind is the symptoms described will happen with a rich misfire - depending on spark strength it can happen at mid-high 10 AFRs. If the OP is comfortable with FC Edit I'd suggest pulling mixtures back to mid 11s and see if the misfire goes away.

Ill try that out, for safety reasons ive left the top rich, ill try to get it to the mid 11's and see how she responds.

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Yes, injectors are on constant power, and when they are not switched on (by having an earth provided through the ECU) you should have 12V BOTH sides of the injector.  Both sides because there is no hot side and earth side when there is no current flowing.  Every point in the circuit is at 12V until the ECU switches the circuit to ground.  Then there will be a variety of different voltages in the circuit.  Seeing as high impedance injectors should be the only resistance in the circuit, then while they are switched on, they should have 12V on the hot side and earth on the ECU side.

The best way to find which side is hot is just to unplug the injector.  Whichever wire has voltage is not the switched side.

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the 6k misfire also happens on idle. maf voltage reads 4.4v just before it misfires it will drop to like 3-3.8 sometimes 2+. and the load point will vary...first it will be like 8k load at 5.6k rpm suddenly it would be at 5k load at 5.9k rpm.

would this be an indication that my maf is having problems reading at higher voltage ? as far as i know 5v its when its maxed. From all my data logs, i noticed a common pattern that it all always happens at abt 4.5-4.6v

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  • 1 month later...

you were right bro... it wasnt the injectors and the afm...
 

would a stuck/jammed vct show same symptoms ?

i recently removed the vct solenoid and tried to power it directly with a battery... solenoid ticks actuator closes oil passage... but no change in idle when i do it with the car running. and no power loss at low end with socket disconnected and driving around.

 

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i got my pulley, and noticed something interesting. all over the internet and included i just got to try out, is actually slightly different on the inside of the gear. everybody else gear seem to have this a more chamferred design compared to mine which is straight up flat. ive searched for hours, and cant find anybody having similar vct gear as mine. i mean wtf right? what are the odds. my gear is the last pic at the bottom

DSC_0017(1).JPG

PIC00160.JPG

post-62707-0-67429600-1330233268.jpg

post-62707-0-69276300-1330233365.jpg

15129457_1568287296518639_6563603603965645069_o.jpg

Edited by Dev RB25
edt
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On 22/11/2016 at 4:44 AM, blind_elk said:

Engine spec appears to be basically factory / stock. Factory spec spark plugs are heat range 5, not 7. And seeing as its basically stock, try opening out the gap a bit. 1mm maybe.

alright im gonna try this out. so far ive tried 0.6 0.7 and 0.8gaps. havent tried 1mm on the iridiums. ill test this out and hope i get the issue resolved.

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On 22/11/2016 at 4:44 AM, blind_elk said:

Engine spec appears to be basically factory / stock. Factory spec spark plugs are heat range 5, not 7. And seeing as its basically stock, try opening out the gap a bit. 1mm maybe.

the gap acutally helped. it revs till abt 6.7k when i release the throttle. it idles like its on 5 cylinders and clears up after 5 secs+- . and when i try to find which cylinder , it always ends up at number 5, ive tried swapping injectors around and same thing.. and i also noticed today, then when i advance (anti clockwise) the cas , my power fc with datalogit reads lower timing, when i retard (clockwise) it reads higher timing... wtf .. is my cas f*ked? or wiring ?

Edited by Dev RB25
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just realised my understanding was all wrong. not sure if it was the threads i was reading or kind of misguided myself. or the way things were said.

i finallly understand the difference between cam timing vs crank timing. what i dont understand is why the service manual says to advance timing is anti clockwise.

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