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v5 Impreza P&P trigger errors

Chris R

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Hi all,

Have a v5 Impreza with g4+ P&P ECU. Was running OK before engine came out and rebuilt. Now, after about 3500rpm have an intermittent problem with trigger errors and rev counter goes crazy (jumps 3500 rpm to over 9500rpm and flicks around in the space of 70-80ms). Have changed both cam and crank sensor for new genuine Subaru parts but made no difference. checked resistance of wiring from sensor plugs back to ECU plug and all 0.3-0.4 Ohms and no signs of breaks or varying resistance when manipulating the connectors.

I looked at the logs but they only tell me what I know is happening. 

I looked at the scope function but seems it can only do a 'snapshot'? Is there a way to actually data log the raw cam/crank sensor signals?

On another brand of P&P ECU I tune there is an option to ignore Sync once the engine is running. I believe the ECU technically doesn't need the cam sensor once running? Does the Link have a similar setting or what would be the effect of unplugging the CAM sensor once the engine is running? I'm trying to separate out whether the fault lies with the cam sensor to the crank sensor (could be both as I believe they share a common white wire)?

Any other suggestions on diagnosing it?

Many thanks.

PS will try and upload a log file.


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The problem is your intake cam is about 20degs more advanced from where it should be, this is causing one of the sync edges to cross over the sync point.  

In the pic below, blue is crank, green is cam, the yellow cursor line is the sync point where the ecu starts counting cam teeth.  You can see I have put a little pink line on the offending cam edge, notice how close this is to the yellow line.  If the cam moves just 1 deg further to the left the ecu will then see less teeth on the right side of that line than it should.  That pink line usually has a good 20 deg margin away from the sync point. 

Looking at internet pictures of EJ cam sprockets it looks like they have about 48 teeth, so if you move it one tooth backwards (~15deg) that should put the cam timing closer to where it should be and solve the trigger issue.


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