(I think I'm on the correct forum now...)

Okay, the other Bonneville, '91 LE. SES light came on day after I left for my 2-week sojourn to Florida. Got home tonight, AutoXray tells me code 41 - cam position sensor failure. Seems to run okay, just that yellow light staring at you.

I knew they have a crank sensor - that went out last year on the '90, but the engine would die when it open circuited. What's the cam sensor do, if the engine still runs when it's failed? Drove it tonight, went to closed loop, no other systems seemed to be doing anything weird (except possibly knock sensor - but I don't exactly know what everything it's telling me should say).

I've never seen this thing. I assume it is unique to the distributorless ignition system. Hard to get to to replace? On the front cover, one bolt, o-ring, connector, etc.? I plan on getting a GM part rather than Neihoff or Sorenson or some other aftermarket brand (assuming the connector didn't just fall off).

Thanks again guys (oh, the '90 seems to be fine now with the new ignition control module and coil pack).

 

I had to replace the one in my wife's Caddilac... it was in the distributor, no big deal. I don't know whether the motor in your car has a distributor or not, but if it does, that's where I'd look.

Her car would run OK after the codes were cleared, then suddenly as it drove down the road, it would either just stop like it had been turned off, or cough severely and then start running again, with the SES light on and a cam pos sensor code . I guess it was losing the cam position signal and falling out of sequential mode into batch-fire mode. $100 and about ½ hour later, all was good.

 

This is the distributor-less system. It hasn't stopped running or refused to start (except when the battery died Saturday).

 

5-7,

I think RB is on to something (as usual). If you don't have the later "Fast Start" system, the crank sensor only measures crank rotational degrees, not absolute position (there are no TDC or "home" flags incorporated in the sensing assembly). The actual engine position is decoded by the cam position sensor, acting as the TDC signal for the system, but not decoding engine degrees. (The Opti-Scrap system does all three functions within a single unit.)
If you have the Fast Start (not sure when it started/ended) you should be able to see/feel TWO notched signal rings on the back of the harmonic balancer sheave. In that case, the cam sensor is used only for injector sequence, not ignition coil sequence. The two interruptor rings on the crank are staggered to indicate engine position. The scheme is similar in function to the EDI distributors on truck engines, but the injector sequncing is different. I didn't know that the ECM would revert to batch fire in the event of a sensor failure, however - I just figured it would go to LIMP with no closed loop control. Again, I learned something today - now if I can only remember it...

 

Yeh, I've had the 3.8s still run great with a dead cam sensor...it usually hides under the water pump...towards the firewall if I remember correctly.

One 10mm bolt holds it on.

 

Any chance it would make it hard to start? When cold, it'll usually fire off on one or two tries. After it's been run, it'll take 4 or more tries to get it to fire, then it's rough for a couple of seconds, then runs like nothing's wrong. If you just try to crank on it, no dice.

Since the water pump is built into the front cover, I assume that means it doesn't have to come off to get to the sensor. But, where you describe is under the power steering pump.

I was under the impression that they did not go to the sequential injection system on the 3800's until 1993. It does have the notched signal rings on the back of the harmonic damper, though, that much I know.

 

Its in the timing cover, kinda hard to see....Its been a while though. ( sometimes I get my head in my **** from all the cars I work on....lol)

Ill check it out tomorrow and let you know exactly where it is...unless you find it tonight

 

5-7,

NOW you're beginning to sound familiar. There was a TSB (or eight or twelve) on that very problem on the 231s without the "Fast Start". You had to crank the engine, shut off, then crank again and it would start delivering correct spark. IIRC, the crank position sensor would lose its reference and fire the wrong coil, or something like that. It's all pretty vague now, but I ran across that somewhere.

Anybody have a better memory than me? C'mon - help out a guy with no memory, will ya? Incidentally, the 231s got SFI as early as 1990 on the performance engines (with MAF).

" * 1990 - 3.8L Buick V-6 in Chevrolet/Pontiac/Canada products (CPC) switched from analog Bosch to AC/Delco FM MAF on high-performance SFI engines only. All other 3.8L and V-6 engines used speed-density systems."

OOH! OOH! I found something else: http://www.motorage.com/edindex/099742.htm

That may give you a better handle on the whassup...

 

OK..my good source tells me its in the timing cover..usually a PITA to get at....

Also tells me that the magnets fall off these things all the time.

 

Cranking then turning the key to the off position puts you back to the beginning. What we have to do is crank, let off, crank, let off, crank, let off, then it will usually start on the next crank or two. If you just grind away, no start. If you crank and back off twice, turn off, you'll crank and back off at least three or four times again before it starts. Really weird. But, it has been doing this for over a year, and the code set for the first time two weeks ago.

Magnets fall off? Great, that means pulling the front cover. The code sets immediately, though, which makes me think it's the sensor circuit itself, not the lack of pulses, that's setting the code.

Oh, interesting reading on the Motor Age page, Vader. Helps explain the problems the other Bonneville was having.

 

5-7,

What I recall is that with one bad sensor it may take more than two full revolutions of the crankshaft for the EI system to "find itself". And you're exactly right about not shutting off the ignition completely, or you're starting the process all over again.

If you get the error code even before you crank, I'd agree that you have a sensor or sensor circuit problem. If you have to crank to generate the DTC, you may have a missing reference magnet. That would bite, especially in a "sidewinder" engine installation. You don't have one of those really "special" 231s where they routed the poly 'V' belt around the engine mount do you? (Where you have to remove the right upper engine mount to replace the belt?)

 

Great timing on this question guys. My old man's 92 Riv just thru this code last week. I was wondering where/what the heck the cam sensor was.

 

Don't have to unbolt the engine to change the belt. One small favor there.

I'll clear the codes, turn it on without cranking, and see if a code sets. Pulling the front cover doesn't sound like any fun, especially when the Camaro needs front brakes and those subframe connectors installed...

 

The sensor is between the ballancer and the waterpump pulley
on the firewall side. Pull the tire and the splash panel out and it
is right there. Takes about 10 min to replace.

 

Just replaced the timing chain damper on my olds trofeo. the next day, I threw the cam sensor code. car is now hard to start in the cold mornings. interesting reading on the crank it, let go crank it, let go, thing.. will try that next time.

Question here is, how do I tell if it's the sensor or the magnet? don't want to pull the cover just to see if the magnet is missing.. I THINK i read a brief tidbit on how to check it once a while back, but I'll be damned if I can find it again.

Thanks guys

 

when you remove the cam sensor, check the cam sensor to make sure nothing has been hitting it...like the magnet. with the cam sensor removed, turn the motor over by hand until you see the magnet (may need a mirror to see). use a metal object to make sure the magnet is still good and strong. if your cam sensor is chewed up, you will need to replace the sensor, magnet, and cam button behind the engine front cover. best of luck, tom

 

B-KARP!

Long time no type, eh? Been hiding in Mukwanago?

You may have a fun one ahead of you, or not. If the engine isn't turbocharged, it's just like everyone is describing. If you're lucky, it's just a sensor or connection.

 

Excellent advice, Tom. That's exactly what I did.

Before seeing your post...

I cleared the codes first, nothing when turning on the key. Started it up, no SES light for about 5 seconds, then code 41. Pulled the sensor (no splash panel on this Bonneville - just frame), the sensor had been rubbed, but not chewed up. Turned the engine over by hand...

It's the magnet. Actually, the magnet is missing in action. Just part of a plastic holder left there.

It looks like it just snaps into the cam gear - correct? If that's the case, and I can get all the old plastic out of the gear, I might be able to put in a new "camshaft interrupter" through the sensor hole without removing the front cover. Otherwise, fun, fun, fun!

 

It's been a while since I did this but I think the magnet clips in
from the back side of the cam gear. You can buy the magnet from
a parts store, not a problem. The problem is putting it in without
tearing down the engine. The back of the plastic magnet housing
has a lip around it, I trimmed the lip away on two of the sides
so I could push it through the hole and snap it in place. It didn't
look reliable but the car has been running for a couple of years
with it.

 

yeah.. correct.. the magnet goes in thrut he BACK of the cam gear.. had to swap it over when i replaced the crappy timing chain damper and timing chain.. Going to pull my sensor tomorrow and look for the magnet.. and also.. pulling the cover is ALOT easier than you might think.. I did mine in less than 15 min. the first time

 

Uncle. I understand how it works now. I'm just going to go ahead and do it right.

I've had Buick 3.8's apart before. This is my 5th, 3rd in a 3800-series Bonneville. First time I've had to get into one of these later ones, though.

Turning the engine back & forth, feeling the cam gear, I think it's also getting timing set and water pump (a little wiggly) while we're in there. And crank sensor (no reason to trust it, having had it fail on me on the other car.

Thanks for all your help, guys. For Karps & swimmster, now you know what you've got ahead of you!

 

yeah buuuddy.. kinda looking forward to it actually.. since I've had my trofeo, it's never really run right.. and come to find out, it was a faulty timing chain DAMPER.. there is a NEW design out now, and it's only $10.. so if you are pulling your front cover, go ahead and replace the damper too.. it's easy. I had bought a new timing chain as well just because of all the raquet the chain was making. turns out my old chain was apparently replaced once. So.. it's like new still.. I put the new chain in just to be safe.. once I finished up, the car ran like it NEVER has run before.. had ALOT more power. then.. 2 days later, I get the SES light and the code 41. must be the magnet flew off or something. hoping it's just a bad connector. BUT.. now that I ahve all the right tools to do the repair, I don't feel so bad. It was pretty easy anyways..

Anyways.. just remember.. if you gotta take that cover off, go get the new timing chain damper as well.. $10 at www.PartsAmerica.com

 

Well looks like I lucked out a mechanic on his mail route fixed it for him N/C guess he had one laying around. Sounded like soemthing I didn't feel like playing with. It's bad enough always working on mine.

Hey there Vader! I've been lurking more than posting. You and Ede cover this board pretty well, and have a much broader knowledge base then me so I've been sticking to the appearance boards where every post turns into a "rice" arguement. Children.

 

5-7,

Some of your perceived "slop" in the chain may be due to the takeup device that rides the slack side of the chain, but since you're going to pull it anyway, you may as well go new. Watch your balance shaft timing marks too (like I have to tell you that - more for everyone else).