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Injectors 1 and 2 not firing. ECU or dodgy injectors?
Hi All,
Chasing High idle and lean condition I posted previously. Jdm bugeye sti ej207
I've narrowed down my issues to injectors I think.
On an oscilloscope all injectors have the same wave form at idle.
CHecked all cabling from injector-plug c22-ecu all ok reading 14.5 ohms from injector cable at the ecu pin and 12v pin on ecu as per wiring diagrams. All grounds bell out and run a temp ground from ecu casing to battery earth incase bad earth.
When i rev the car in neutral injectors 1 and 2 don't show that they are firing it just Flat lines. Once the idle returns to 950 which is still high the pattern returns. This is even with a few sec horizontal plane ot doesn't pick up anything.
If I unplug injector 1 injector injector 2 gets a sort of half max peak wave but still way smaller than when it it returns to idle.
Injectors 3 and 4 show a correct pattern when reved as in more peaks appear on the oscilloscope as the injectors duty cycle increases.
1 and 2 appear to work when u rev it cold though its only when it warms up.
Is it possible the ecu is faulty rather than the injectors? Or could 1 dodgy injector drag down the other one as electricnically they might be firing from the same electronic circuit ?
I'm confident its either injectors or ecu but it seems weird i wouldve lost 2 injectors at the same time.
I can email someone the video of the oscilloscope.
Help appreciated
Last edited by Bbtr; 15 September 2024 at 06:42 PM.
Standard ecu and car V8 on the large sticker on it.
Its def injector 1 and 2 as per the ecu pinouts and confirned with the colour of the wires from ecu plug- brown engine harness b22/e3 behind battery-injector.
I mean I kinda know my answer. Replace the 2 injectors with known working and see happens. It's just weird it fires them when idling then doesn't when it gets warm. Like a coil is breaking down in the injectors once it gets hot and pulling to much current and the electronics maybe stops firing them to save something.
Here's 2 screen shots ignore the noise on the horizontal I knocked the earth clip off Idling waveform looks same as other cyl. Waveform has same shape when zoomed in etc same spacing across the screen This is the car free reving at approx 2500rpm. No injector pulse lean sounds like its running on less cylinders. Then returns when off the pedal goes and it eventually sorta figues out its idle again. Ignore the noise on thr horizontal when i was filming i knocked the earth clip off.
If you hold the throttle at 2krpm it will eventually throw a 1507 code which is my original issue. Now when the engine light comes on the ecu turns off injectors 1 and 2 almost like some weird limp mode.
I don't think this is my issue.
When the AC is on the ecu stays in closed loop and will more or less happily sit at 2krpm with all 4 injectors firing confirmed with the oscilloscope.
Its when the ecu ****s itself for whatever reason holding rhe throttle ar 2krpm it throws the code then shuts off 1 and 2 only
This might be of value to someone chasing a high 1507 code.
Neutral position is fine changes state 12v in gear 0v out of gear. Confirmed by testing pin 8 plug 134 which is last plug on the ecu to the right with the clips at the top.
From the rabbit holes ive gone down im reading the nps only mucks around with avcs not engaging. I've logged cam timing left and right and nothings jumping out like the avcs solenoid is sticking as they are in sync.
B22/e3 is the brown plug behind the battery.
I'm leaning towards a vac leak again even though ive plugged stuff smoke tested vac tested intake pipe listened for leaks etc. The throttle off the IACV pulse width with oscilloscope is 2.25ms which suggests its fully open before the engine starts. When it starts the pulse width increases to nearly 4ms to try and bring the idle down which is does to a certain degree. When I turn the ac on the pulse width drops back to 2.2ms for a sec and the idle blips up as if this would normally stop the motor from stalling with the extra load but as there is probably clearly a leak it quickly reverts back to 4ms pulse width to try and get the idle down.
has s rough idle aswell. Think I'm gonna throw a set of flow tested injectors and replace all intake gaskets/ block up the intake manifold when it's off and vac/boost test it.
I doubt it's down on comp i dont give it a hard time and as it just threw this code out of the blue one morning.
tps reads 0 and seems to read linear up to 100%. Throttle plate closes fully and cleaned even though it wasn't dirty. New crank case breather valve which wasn't an issue either.
New chinese iacv. This helped considerably from the original one I removed and cleaned up freed to the pint I thought it was fixed but idle still hangs when throttle blipped. When it runs lean I think its jist the ecu assuming it's in decel and turns of injectors.
fuel pressure and reg responds as it should when you disconnect vac line to fpr ie fuel pressure increase approx 9psi from 43psi. Fuel sock is clear nothing in the tank. New fuel filter.
It has a new set of plugs gapped correctly 0.8mm checked with feeler gauge denso ik22s. I swapped out my old coil packs which i knew worked mostly but were causing a miss years ago when under boost.
I'm running out if ideas and feel I've covered all bases. It ran lean with the brief full load few pulls with afrs of 12.5 where it would normally be 11.3 with the same load grams/sec rpm and boost levels from old data logs. Sort of suggests pre turbo leak but boost and vac leak with the turbo outlet blocked and maf opening blocked and t offs blocked and it held pressure and vac for like 20secs i can only think the pressure bleeding off slowly might be through the turbo impeller seals or something but it bleeds of slowly with 14psi in it and vac. no bubbles anywhere no audibility hissing. Smoke tested same arrangement still nothing.
Last edited by Bbtr; 16 September 2024 at 08:56 PM.
Swap the injectors around and see does the fault move. No point in throwing parts at it, I know where C22 is was just checking were we on the same wavelength.
Not sure exactly. Found it in the many rabbit holes ive been down.
So far the colours and pin outs have been accurate confirmed by tracing to the plugs as per the audm wiring diagram. The audm ecu pinout colours don't match but the wiring to plugs and earth points seem to be the same so far jist different coloured wires for the jdm pinouts.
15 September 2024, 06:39 PM
Injectors 1 and 2 not firing. ECU or dodgy injectors?
