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Cam sensor


djeanotte
03-17-2008, 08:12 PM
I have a 91 Delta 88 with a v6, front wheel drive, 145,000 miles. Recently the check engine light came on. A garage determined it was Code 41, cam sensor. The light comes on only after running for a while as if the engine needs to warm up before the light goes on. Additionally it goes on and off at first and then after it seems to get completely warm the light stays on. I replaced the cam sensor but the same problem persists. The cam sensor wires seem ok. Car seems to run fine with the light on--although I have not checked the gas mileage impact. Questions: What else could be causing the Code 41? What if I just ignor it as it does not seem at this point to be impacting the operation of the engine? Thanks

MagicRat
03-17-2008, 09:53 PM
Hi,
My '88 Bonneville, (3800 V6, same engine as yours) developed the same problem.
Likely, your cam sensor itself is fine; it's the magnet on the camshaft which is going bad. This was a common problem, but difficult to fix because the engine must be removed to get the camshaft out.

This cam sensor circuit is only used to initially time the EFI system on initial start up. So long as it produces a reading when cold when you crank the engine, the EFI will work properly, even if the signal is lost as the engine warms up.

The problem you may have is a 'hot' start because, at that time, you will have no signal. At this time, the EFI system will go into a default mode where, instead of firing fuel injectors sequentially (one at a time) it will fire them two at a time, (because the EFI computer is unsure of the exact start position of the camshaft)

I drove my Bonneville thousands of miles on this default mode, with no bad effects. I noticed there was occasionally a very slight (most drivers would never notice) hesitation when accelerating.
Gas mileage was not affected, and full throttle acceleration was slightly faster (!) than during normal operation, probably due to a slightly richer mixture.
Also, my emissions were as clean as ever.

Personally, the repair for this problem would easily run over $1000. This is a lot of money to solve a problem which has no real-world symptoms except for the 'check engine' light. IMO just drive the car and do not bother fixing the problem. It may be reasonable to scan for codes at each oil change to see if any additional codes have appeared, (indicating possible unrelated problems)

You an easily scan for codes yourself on these GM cars, you do not need a garage to do this for you.

Geirskogul
04-20-2008, 12:34 PM
I disagree when you say that it shouldn't be fixed. If the magnet itself drops completely, you could have problems with the car dying on acceleration, or even at idle! Though, "properly" fixing the problem involves taking it to a mechanic and letting them clean out your wallet, you can easily fix it yourself.

First, buy the magnet from any shop like Autozone/Shucks/Napa. They'll have it listed in their computer as a "Camshaft interrupter magnet," and it should run you about $11. Buying it from the dealer will run you $40, so watch out.

The magnet itself is shaped like a top-hat, and designed to be pushed in from behind the timing gear/sprocket. That's why the repair is so expensive, because mechanics have to basically dissassemble the whole accessory side of your engine to push it in from behind. You can, however, just file or dremel off the "brim" of the magnet, cover it with epoxy, and push it in from the front, though the camshaft position sensor hole. I've done this fix and run about 11,000 miles with no check engine light.

I used this guide to help me with my repair.

http://bellsouthpwp.net/p/a/padgett46/cammag.htm

Tools you will need: Socket set, Camshaft interrupter magnet, epoxy, file, mirror-on-a-stick (mechanic's mirror), metal pick (to get any broken pieces out), q-tips and rubbing alcohol (to clean it off before JB-welding)

zoman
04-23-2008, 12:53 PM
hey guys, so if the magnet is gone, will this cause engine to stall?? I have this 89 eighty-eight that's doing this...runs great when cold but once it warms up it starts acting up...code 41 and MIL always on.

maxwedge
04-23-2008, 03:00 PM
Cam sensor issues can cause performance problems and hard starting ,but will not normally cause a dead out stall or complete failure to start, regardless of the misinfo pertaining to this malfunction. Personally I would fix but then I have my own shop. Some people don't have the skill or money.

Geirskogul
04-23-2008, 03:04 PM
Cam sensor issues can cause performance problems and hard starting ,but will not normally cause a dead out stall or complete failure to start, regardless of the misinfo pertaining to this malfuncttion.

I never had a complete failure to start, but when there was only a partial magnet there on my car (and later when it completely disintegrated) I would have it occasionally stall on accelleration, after it warmed up. The warmer the engine got, the more the gas pedal would "lag", and then it would utterly and completely stall out. After replacing the magnet, both the engine code and all trouble was gone; so I disagree.

It's not an expensive fix to do it yourself (and I did it whilst knowing almost nothing about cars, three years ago), so get it done.

maxwedge
04-23-2008, 06:27 PM
Disagree huh, boy you are on a track here, in 1988 the loss of cam sensor input causes the pcm to go to " batch fire" as opposed to mpfi or sfi, this will cause, as I said performance issues, but to have stalling, as I said normally is is not part of the symptoms, so your 20 year old car did and you insist on disagreeing with what has been stated, read both mod's posts and you will see no one is discounting the rare possibility this can occur, lets put this to sleep, okay.?

zoman
04-23-2008, 07:57 PM
well, the missing magnet issue needs to get fixed, so i'll fix it and take it from there, maybe I'll luck out and all issues will go away...thanx guys.

luckywrench75
12-08-2010, 01:08 PM
if you are pulling a 41 cam sensor malfunction code, the first thing you should do is disconnect the battery and remove the sensor from the side of the motor. Then rotate the crankshaft while holding a mirror to see inside to the cam gear. there will be two visible bolts and next to one, there should be a magnet protruding 1/8 inch or so from the surface of the cam gear. also notice on the sensor itself for signs of this magnet rubbing against the sensor plate. if there is no magnet, theres your problem, however; if the magnet is still there and it is an intermittent code that depends on engine or air temperature, the magnet is losing its polarity which characteristics of is needed to properly function with the sensor. also look in the connectors for corrosion as a lack of resistance could run the same code. the easiest and most affordable way to replace this magnet which is only 10 bucks, is to remove all traces of the old piece while being careful not to let any debris fall into the motor and filin the edges down on the new magnet. it is intended to go from the inside out holding in place with two round ears on each side. you can file these ears down and put it in through the front with some strong epoxy. be sure to have the filed end into the motor first as the polarity of the magnet is important to properly work with the sensor. now with a new magnet, a new sensor, and a new pigtail, this code should erase immediately. but if you still have an intermittent code, more than likeley it is accompanied by an engine tick sounding like lifters. thats the valves hitting the pistons because the timing chain is too far stretched. in this case you need to change the chain, gears and valves. you canfind a cheap timing set for 40 bucks or you can get an edlebrock performance set for 65. valves are all over the place so look around for those.

luckywrench75
12-08-2010, 01:11 PM
all that a missing magnet will do is cause the injectors to fire twice instead of once watch the O2 monitors, the banks will show lean but the o2 sensor will indicate rich. if ur stalling, then id make sure there are no additional codes with a different scanner

maxwedge
12-08-2010, 03:50 PM
Good info, but check the dates before posting this is an inactive 2.5 year old thread, thanks.

Bear
12-21-2010, 12:12 PM
Just going to post this same issue, thanks to all for the inputs. Pray for me I am going in.

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