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3800 question

  #1  
Old 05-14-2011, 02:27 AM
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Long story short, I traded my Blazer for my mom's 1989 Buick LeSabre Limited. It has 140k on a vin C 3800 SFI V6. Anyway, it was stumbling at idle in park or neutral and had a vibration so I changed the plugs and wires and ran 91 octane and seafoam through the tank. I got it back yesterday and it has a steady vibration in gear that shouldn't be there and a horrible hesitation right off idle in gear. I never checked to see if the plugs were gapped correctly, could that be why? The Service Engine light is always on due to a nonexistant cam sensor (it had a hesitation, but only if you got on it hard suddenly). Tried to make a vid showing what's going on but my phone froze. When I finally got it to work, the hesitation was gone but the vibration was still there. It had the hesitation still after running almost 30 mins and driving 12 miles (and earlier throughout the day but I didn't figure it out until later). Any ideas? Injectors? Fuel filter (new pump)? Dirty coil packs? Aliens? Thanks for input
 

Last edited by nineTnine; 05-14-2011 at 02:29 AM.
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Old 05-14-2011, 05:31 AM
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I would check for a vacuum leak, also check the egr.... what worries me is the non existent cam sensor, was it removed previously or did you remove it, check into getting 1 back on there. I would say that is why it is missing and stumbling, I am pretty sure it is needed since you cannot adjust the timing on it since it runs coil packs. Hope this helps
 
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Old 05-14-2011, 12:56 PM
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No the cam sensor itself is relatively new, I replaced it myself a few years back. However that didn't fix it and I found out later that whatever matched up with the sensor inside the engine is plastic (another brilliant idea) and as time goes on the plastic gets brittle and snaps. It did have a hesitation before but it was only if you got on it hard and it would just be one biiiig hesitation, so big I thought the engine would die before it would go. But this one is different, its right off idle and is a repeated stutter. The car likes to try to die a lot going into gear but it has gotten better since the plugs and wire change, dunno how but I had a hell of a time before them, it would die two or three times before I got it to mov every time. Dunno what that's about either if its somehow related or not. I was told to check the throttle body for buildup and spray carb cleaner in there. Was also told it is somewhat dangerous with the engine running
 

Last edited by nineTnine; 05-14-2011 at 01:00 PM.
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Old 05-14-2011, 06:13 PM
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Originally Posted by nineTnine View Post
No the cam sensor itself is relatively new, I replaced it myself a few years back. However that didn't fix it and I found out later that whatever matched up with the sensor inside the engine is plastic (another brilliant idea) and as time goes on the plastic gets brittle and snaps. It did have a hesitation before but it was only if you got on it hard and it would just be one biiiig hesitation, so big I thought the engine would die before it would go. But this one is different, its right off idle and is a repeated stutter. The car likes to try to die a lot going into gear but it has gotten better since the plugs and wire change, dunno how but I had a hell of a time before them, it would die two or three times before I got it to mov every time. Dunno what that's about either if its somehow related or not. I was told to check the throttle body for buildup and spray carb cleaner in there. Was also told it is somewhat dangerous with the engine running
So was the plastic piece that matched up to the cam sensor broke when u put the new cam sensor in? if so then that is your problem. Take the Egr off and give it a good cleaning, make sure its not stuck open. I know on the 2.8 and 3800 if the egr valve is stuck open it will cause it to die when you stop at a stop light etc. You can go ahead and clean the throttle body with the cleaner, its only dangerous if the engine is backfiring, also could run some seafoam thru the vacuum system off the vacuum line from the brake booster
 
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Old 05-14-2011, 07:14 PM
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I would bet that plastic thing broke and that's why it threw the code instead of the sensor itself, seeing the new sensor did nothing. We've had this car for going on 4 years and it hasn't done these things before. Like I said, it would have a hesitation but only if you like stomped it from a stop or revved it hard you could hear it hesitate. This only happened while it was in gear and taking off from a stop like normal. I drove it today and it didn't do it I don't think but did it all yesterday so now I'm confused. And I have no idea how to seafoam a vehicle other than through the gas tank and I'm not sure what the egr is. What is the proper way to seafoam something? I don't think it says on the can. Thanks for your help!
 
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Old 05-14-2011, 10:35 PM
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Yeah I would look into that cam sensor not reporting and fix it, let us see what you are talking about and maybe we can come up with a way to repair it. Where is the location of it on this engine, how can we open it up for a repair of this plastic? Cleaning the throttle and sensors in the intake never hurts too. 3800s are a badass engine. The cam sensor must still be functioning, in my experience engines dont like to run with them unhooked or faulty.
 
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Old 05-15-2011, 09:07 PM
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Upon further internet research I found out I was on the right track. The car had thrown a code 41 if i remember correctly and what i found seems to confirm this. It is a cam sensor fault. These engines have a magnet on the end of the cam that goes by the cam sensor called the interrupter I think. The magnet housing is plastic and after awhile has a tendency to break, flinging the magnet into the black depths of the oil pan. What this forces the computer to do is run off the last known good cam signal. That is how I understood it. This website was very helpful and has a write-up on a posible fix.
View topic - Code 41 Diagnosis on Vin C LN3 3800 : PontiacBonnevilleClub.com
The Padgett one is the write up. It doesn't seem too difficult but I'm wondering what the clearance between the timing cover and the cam magnet housing is because I'm wondering how to get the broken pieces out of the hole. I think if i use an awl or something to breakup the housing, the pieces will fall in the engine? What do you guys think? I doubt the timing chain has ever been replaced in this car before, it has a timing chain in the engine not a belt right?
 
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Old 05-15-2011, 09:57 PM
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Yeah if you can not see the timing belt/chain, then its a chain. Ive never seen a belt inside the engine, and only seen belts on exterior cam gears. You should give it a try for sure. Use a vaccum to clean up the bits as you awl it out.
 
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Old 05-15-2011, 10:08 PM
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I was going to give it a shot this weekend when we trade cars again. I don't think I have a small enough vacuum to get the pieces out, any other ideas on how to get the pieces out? Then I need to find a way to keep the magnet from dropping back into the engine when I try to put it back in
 
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Old 05-16-2011, 08:11 PM
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Well, it is a magnet after all, so it will stick to something that is ferrous metal and that is also too big to fall into the engine.

I read through that link, and I would use the JBweld to attach it as well. I would also drill a tiny hole or two into the magnet, and also into the cam where its going to mount so there is more surface area for the glue to bond to.

Im sure your vacuum will work fine.
 
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