[Gmecm] erratic 3.8L Cam sensor alarms

[Ron Drew]

Many thanks Scott; I think that you have led me to the problem. I understand 
that the magnet is not replaceable; so I'm planning to replace the timing 
set.

Ron

----- Original Message ----- 
From: "Scott Feaver" <sfeaver at magma.ca>
To: <gmecm at diy-efi.org>
Sent: Sunday, October 08, 2006 10:52 AM
Subject: Re: [Gmecm] erratic 3.8L Cam sensor alarms


>I had my magnet come out of the sproket at about 130k miles.   Its held in 
>a plastic retainer and it disintegrated.    Maybe its starting in your 
>case, and its position drifts slightly back where the sensor wont pick it 
>up..
>
> Scott
> ----- Original Message ----- 
> From: "Ron Drew" <rjdrew at adelphia.net>
> To: <gmecm at diy-efi.org>
> Sent: Sunday, October 08, 2006 10:09 AM
> Subject: [Gmecm] erratic 3.8L Cam sensor alarms
>
>
>> Has anyone experienced problems with a GM 3.8L (1989 with 122K miles) 
>> missing cam position pulses? More specifically, the pulses generally 
>> begin to miss when the car has been driven for a while on warmer days; 
>> and it only seems to trigger the alarm at lower speeds.
>>
>> This what I have done:
>> - I replaced the ECM with a known good spare which did not help.
>> - I've tried a couple of different brands of sensors, which did not help 
>> (they all behave the same).
>> - The crank sensor works flawlessly; the cam sensor shares the same '+ 
>> volts' & 'ground' with the crank sensor, so any problems with the '+ 
>> volts' and 'ground' would need to exist on a very short run of wiring 
>> between the Crank and cam position sensors.
>> - I have not yet scoped the sensor line going back to the ECM.
>>
>> I suspect the problem may be with the position indicator mounted on the 
>> cam sprocket. I don't know if this is a permament magnet or a normal 
>> piece of metal. As far as I can tell there is no magnetism in the 
>> position indicator. BTW I may go weeks and not see an alarm, so the 
>> problem can be very erratic.
>>
>> I thought I'd check here and see if nayone has experienced this or has 
>> any ideas.
>>
>> Thanks
>> Ron
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>
>
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