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Subaru B4: Cam Shaft Sensor and/or Alternator Issue


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#1 LukeFranky

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Posted 05 January 2016 - 10:31 AM

As mentioned in my previous threads I have a problem with my cam shaft sensor playing up and misfiring at idle.

 

Problem occurs initially at start up or after coming to a stop and idling for a little bit. It gets worse with the (HID) lights on. Hesitates on initial take off. Engine light flickers too. Stored code points to cam shaft sensor.

 

It started 9 or more months ago, but wasn't as bad as it is now. Assuming it was a bad ground I added extra earth wires and the problem disappeared but it has slowly crept back. Removing the extra grounds makes it run so much worse now.

 

I have tried replacing the sensor so I suspect the alternator now. I have checked my voltages at idle and they drop below 11V at times with the HIDs on. Battery has been already been replaced.

 

The voltage sits on 14.4V with the engine revving and the cam shaft sensor stops playing up. The misfire seems to be in tune with the battery voltage. It doesn't play up instantly at idle, it is only once the voltage dips.

 

Am I right to suspect alternator, or should I be looking elsewhere first? Alternators are expensive so I want to be fairly certain.

 

 

Someone told me that Libertys have an ECU controlled alternator and that might explain the voltage drop. Is there any truth to that or am I wasting my time even thinking about it?

 

Lastly, if I do need to find a new alternator. What's the most cost effective option? Ebay? Secondhand?


The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#2 andrew_k

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Posted 05 January 2016 - 11:22 AM

Used alternators aren't too pricey, and are widely interchangeable. If you find a GEN 5 one that'll be 130A output instead of the 90A or 100A output of your current one. A tidy upgrade if you can swing it for $10 extra.



#3 LukeFranky

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Posted 05 January 2016 - 12:04 PM

Might try that, but before I spend any money can you or anyone else confirm GEN5 alternators fit a GEN3 B4 without issue?


The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#4 LukeFranky

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Posted 05 January 2016 - 12:07 PM

Also, from my research I think my current alternator is 110amp.


The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#5 andrew_k

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Posted 05 January 2016 - 02:08 PM

all the EJ alternators fit each other AFAIK. There is a slight difference with the some wiring harnesses not utilising the control pin on the alternator, but sockets are still the same, mounting brackets still the same. It's an extremely common mitsubishi alternator, if you stick a photo of one into google image search you'll see it used in  many different vehicles.

 

Someone might have a spare you can borrow to check. If you were in VIC I'd lend you one.



#6 Adam

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Posted 06 January 2016 - 08:19 AM

I don't think that's entirely true. I thought there were different types. Eg round and square plug types. Maybe just on the earlier models?

Posted Image

 

#7 andrew_k

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Posted 06 January 2016 - 09:40 AM

Interesting! I know my MY99 SF alternator has the same plugs as my MY03 GD one. Might indeed be earlier gens. Keen to know :)



#8 Reevesy

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Posted 06 January 2016 - 11:36 AM

Early ones had a round plug.

Later have a square plug

#9 LukeFranky

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Posted 11 January 2016 - 09:02 AM

Did some more testing.

 

Turns out the camshaft sensor does also play up when the voltage is within range. Battery voltage certainly affects it more, but that isn't a the sole cause.

 

Measured the resistance between the camshaft plug and the ECU and found a problem one line 2. Workshop manual says it is meant to below 5 Ohms, but resistance was sitting at about 7 Ohms.

 

Played around the cables and cleaned the plugs, resistance dropped to 2-3Ohms but the issue got worse after my fiddling around. Must be a cabling issue.

 

Bought some shielded cable, going to run new lines straight from the cam shaft sensor to the ECU.


The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#10 duncanm

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Posted 11 January 2016 - 09:56 AM

Doesn't sound like a bad idea.

 

Be careful with the shields.  Factory wiring is shield broken at plug 'B20 / E1' - in the engine bay.  ECU side is grounded to ECU, engine side grounded to chassis ground (I think the ground at the pitch stop mount).

 

Did you clean all the engine harness plugs ?



#11 LukeFranky

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Posted 11 January 2016 - 12:47 PM

Will it be important to ground the shield in the same manner? Half to chassis and another half to the ECU?

I was thinking of simply grounding the shield to the chassis only since I will be bypassing the plug between the ECU and camshaft sensor?

The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#12 allpaw4

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Posted 11 January 2016 - 06:28 PM

Just make sure that the shield is only grounded on one side. Ie if it's split like factory, you don't ground both sides of each run. Once you ground both sides it no longer shields anything.

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#13 LukeFranky

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Posted 14 January 2016 - 12:10 PM

Yesterday I got busy with the soldering iron. Grounded one end of the shield to the chassis near the ECU.

 

The last few days beforehand it was running very poorly on startup and so far it has improved noticeably. There is still an initial hiccup just as the engine starts but it smooths out quickly. Since it is a problem that comes and goes to varying degrees only time will tell if I have made a real difference.

 

At least I didn't make it worse. I was half expecting to.

 

My timing belt is due so I'll do that next. What's left of the symptoms might be a stretch in the belt or the alternator.


The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#14 LukeFranky

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Posted 14 January 2016 - 04:38 PM

Found this: http://www.uklegacy....bling-idle-etc/

Says alternator is a common cause for this issue on Rev D Libertys. His symptoms sound all too familiar.

Back to looking for a new alternator I guess.

The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#15 Fungry

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Posted 15 January 2016 - 09:17 AM

Yep, definitely alternator. Spent a good week troubleshooting this issue on my rev D B4 checking sensors, timing belt, alternator voltages etc. Ty and me traced it down to the alternator after noticing it happening under load eg HID's on, running air con etc.

Just be careful with what alternator you install. I used an alternator from JDM rev a-c and the problems persisted. Once a direct repelcament was sourced all was good.

 



#16 LukeFranky

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Posted 15 January 2016 - 10:22 AM

Ah, I was just looking at an alternator from a Rev C.

 

Where did you end up sourcing a working alternator from and how much was it?


The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#17 LukeFranky

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Posted 15 January 2016 - 01:58 PM

I've been told this will fit:

http://www.ebay.com....0-/231666364686

 

Looks generic, but 100% good feedback for all the other alternators they have sold and decent returns policy are tempting me. Opinions?


The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#18 Dinka

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Posted 17 September 2016 - 03:42 PM

Did the problem go away after the alternator was replaced ? 



#19 LukeFranky

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Posted 19 September 2016 - 08:36 AM

Yes it did.

The B4 Bomber - 2002 MY03 Subaru Liberty B4, ADM, Manual, EJ208. 


#20 Grant B4

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Posted 08 January 2017 - 11:36 AM

Luke - did you end up going with the eBay generic alternator per your link two posts above?

 

I have the same CPS code which goes away once you rev the engine to produce more amps, and causes a miss on one cylinder at low RPM. Replaced CPS to no avail. Checked all coil packs. The more electrical load you put on the engine (ie. lights, fans, rear heater, audio), the more current you need to produce from the alternator to make it go away, to the point where at night when headlights are on, I need to be above like 3k RPM for it not to miss and the CEL to dissappear.

 

I suspected alternator and pulled it apart to check brushes, do a diode check, and visual inspection. All good. Weird that mine first started playing up after torrential rain - I suspect that maybe rain seeping in through bonnet scoop may have forked with the transistor block or caused a partial short in the windings.






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