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Subaru 01-05 PNP - 2 IGN Outputs Not Working


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Hoping someone can shed some light on this situation. The vehicle is a 2004 JDM Subaru STi. The car has been running the ViPEC for quite a few years with no problems, and a few months ago the cams were changed but they had the wrong triggers (US market). The AVCS and the AVCS camshaft sensors were disabled (adjustable cam gears have been sourced), and the car has been driving for a couple months like this with no issue. The owner informed me the car just started misfiring while cruising on the way home and then just died and wouldn't start back. After some diagnosing it was found that cylinder 3 and cylinder 4 ignition coils were not firing while cranking (except for sometimes one fire after cranking stops), while coil 1 and coil 2 are firing fine when cranking. When using the software ignition test all of the coils fire perfect, ruling out faulty wiring or coils. As of now we have changed the main camshaft sensor and the crankshaft sensor. RPM is reading fine while cranking.

The ECU was on old firmware, 4.6.9, but so as to rule out, unlikely as it may be, a firmware issue, the ECU has been upgraded to the last firmware for the V44.

Any ideas as to what may be causing the issue?

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I would be very suspicious that the cam timing has changed / moved. On the early non vvt crank / cam triggers it only takes a cam to be out by 1 tooth to cause issues.

You might be able to see this in a log of the Dwell time or there might also be trig 1 errors counting up.



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Hi Simon,

Thanks for the reply. It's doubtful it could be cam timing for two reasons. It happened after a couple months of driving with the latest setup which had the AVCS disabled and USDM cams installed, and in the middle of the drive just cruising on the way home. The guy works for the local Subaru dealer and is certified on Subaru and Mercedes, and he has since torn the engine down to perform some checks and upgrades and put it back up. I asked him last night about the possibility of cam timing and he assured me that was on his mind as well, so he checked before the pull down, and double checked when it went back together. He did say he is going to install the adjustable gears and see what happens.

I did see trigger errors slowly counting up as he was cranking. I asked him to check for continuity between the camshaft sensor connector and the ECU.

This weekend I'll also log the dwell time.

If there is anything else you can think of please let me know. Thanks.

Edited by pioneer_sti
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Hmm the trigger errors point to issues around the cam or crank sensor. It will clock errors if teeth are not seen or if there is extra teeth (noise) on either input.

It might be a case of having to put a scope on the triggers to check the signals.


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It did turn out to be crankshaft signal related. One of the teeth on the crankshaft had minor damage, it was even hard to spot it, but it's working now after changing it. Amazing that it worked with the damaged tooth for so long and then suddenly in the middle of a drive decided to stop, but after 15 years of working with ECUs, nothing much surprises me anymore :)

Thanks for the help. 

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