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Old 04-25-2015, 01:18 AM   #1
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Default Cam sensor code, ignition weirdness; need an oldsmobro'* wisdom and guidance.

Hey so I have a 1990 oldsmobile 98 regency broham equipped with the fire breathing hell machine that is the legendary fuel injected 3.8 liter V6 and she has about 170k miles under her proverbial belt. After years of loyal and uninterrupted service she decided to take a dump in my face. About a year ago my mass airflow sensor (I believe at least, ití* been throwing code 34) went out on me and I've been driving it ever since with no major issues, she just doesn't have as much power, runs a bit rich, doesn't like to idle and usually dies after I start it up after the engine has been ran and warmed up, and doesn't like to shift when I give her the onion. Other than that the thing runs fine; however I don't think that has anything to do with my big problem that came up the other day.

So I was driving her along and everything was great, I didn't have a care in the world, but then suddenly and without warning my world came crashing down on me. The engine started running like hell, super rough, sounded like it was only firing on 3 cylinders. Has no power off idle, but if I get it to rev high enough or up to high enough speed to allow for revs it kinda comes out of it.

I barely got it home, but once I did I immediately swung my baseball cap to the back got straight to business. After jumping the A and B terminals in the computer plug in thing and turning on the key she laid it all out for me. The computer threw 34 (nothing new), 41, and 63. I looked up the codes on the World Wide Web and according to troublecodes.net code 41 is a cam position sensor and for 63 it says "incorrect EGR opperation".

Thinking that it would be a quick fix, I hauled some moderate *** to my local Oíreilly auto parts and picked up a new cam sensor. Hauled *** back home, threw it in, eagerly hopped into my car stoked to have my car back, turned the key, and nothing. Still doing the exact same thing. Still throwing the same code too. So I tore off the EGR valve to see if anything was obviously wrong with it. There was no major carbon build up on it to speak of; just a little layer that I wire brushed off. I put the thing back on and hooked it up and tried it again and nothing changed other than the computer stopped throwing the EGR code.

My mechanical understanding isn't hugely impressive, but I can do a few things on my own. To me, it seems like the ignition is firing way too early, or maybe the engine jumped time, but I kinda doubt that. The thing doesn't like to start at all. When I go to crank it, it will turn over and I can hear it try to fire on a cylinder or two and then the engine will usually just stop (like a cylinder fired too soon). I can eventually get it to fire up but it takes a good few tries to do so. Once it does fire up, if I rev it up enough (as stated before) it smooths out a bit, which would make sense if ití* just the ignition firing too early right?

I have no idea if the cam sensor I got is any good or defective or if my wiring went bad or a ground or something. I'm not even positive that my ignition is firing too early either, it just seems like it is to me. I'm not really sure what to do next as far as diagnosing goes. So if one of you worthy bros could help me out I would greatly appreciate it.
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Old 04-25-2015, 02:43 AM   #2
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The first thing to check in your situation normally is the Cam sensor interrupter magnet. You pull the cam sensor out, peer into the hole straight on (usually a mirror is needed for this) and crank the engine over by hand until you see it in the camshaft timing gear.
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Old 04-25-2015, 02:51 AM   #3
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Should look like this:


If it looks like the magnet has blown out of the center of it, you are left with two options. You can try jb welding another magnet through the hole into the remnants of the magnet casing, and hope that it fixes it, because if it don't, you will need to remove the magnet casing, and install a new one through the back side of the cam gear (think of the labor as replacing the timing chain essentially).

The computer uses the cam sensor to detect when cylinder 1 is passing by to coordinate injector timing. The engine primarily runs off of the crank position sensor. So, what happens is that the engine just starts the injector sequence at #1, no matter where the engine is, so fuel injection timing is off. There is a 1 in 6 chance of it getting it right essentially.
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Old 04-25-2015, 02:16 PM   #4
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Also, been running rich for a year with a bad MAF? Could be your cat is plugged and causing that EGR code....
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Old 04-25-2015, 05:42 PM   #5
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Make sure you check the wiring right by the cam and crank position sensors. On my '93 Delta, the wire shielding was worn down and the copper was making contact with the block.
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Old 04-27-2015, 12:04 AM   #6
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Hey thanks a ton dudes! I'll check out that interrupter magnet thing you were talking about tomorrow rjolly87, is it a semi-common thing for those to puke out their magnets then? Hopefully the thing hasn't gone and exploded somewhere in the engine and done some other choice damage for me.

Tech II, I live in Montana where we are blessed with the privilege of no emissions tests, so I hacked those turds off long ago and cashed em in for like 50 bucks, but I wonder if it running rich could be causing other issues for me. I like to give her the sauce on a regular basis to try to keep carbon buildup to a minimum, but I wouldn't be surprised if I still got some growing somewhere.

Martinnhs12, I didn't notice any obvious ruptures in my wiring when I replaced my cam sensor, but I will definitely check that out as soon as I can as well.

Thanks again guys, I really appreciate it. I will report back with my findings here when I have a chance to check the thing out again.

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Old 04-27-2015, 08:19 AM   #7
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I wouldn't say it'* really common but I think it'* bound to happen to every LN3 at some point in their lives. The plastic degrades with time and cuts it loose. Usually the magnet gets stuck to the engine block inside the timing cover and stays put, so if it hasn't caused a problem already it probably won't, assuming it'* not where it belongs.
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Old 04-30-2015, 03:30 AM   #8
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Glad to help, Kevin.
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