89 bonneville strange problem

Biomistake · 10-27-2012, 07:54 PM

Hello all. I just was given a 89 bonneville le with a 3800 series motor. I'm having a slight issue with it. It wants to stall out when the engine is cold. It is a hard start unless I feather the pedal then it starts but will stall untill the temp gauge comes over C (100°). At this point it's able to be restarted and driven ok but after driving on the highway the idle will be high. The check engine light is on but I dont have a code reader. The person that gave it to me said it either had a cam or crank position sensor sensor error. Also said something about the timing belt threw a magnet. Also at times, especially when cold, way les frequently when warm it seems to miss a cylinder and chug a bit. Is my problem the magnet on the cam sproket our the tps or a combination of many different things? The mass airflow sensor has been replaced, the fuel filter has been replaced. Any thoughts? Thanks

MagicRat · 10-27-2012, 11:53 PM

I swear, ALL of these engines eventually develop a cam position sensor failure. The sensor itself is fine, the magnet on the end of the cam falls off or ceases to send an adequate signal.

All this sensor does is, when cranking, allows the ECM to time the fuel injection system for sequential injection. When this signal is lost, the ECM goes into a default mode, where the injectors do a batch-fire (I think two fire off at a time, instead of one).

I found the idle to me slightly rougher when in default mode, but the WOT power increased slightly, with no measurable loss in economy. I did not experience the other problems you describe.

I suggest you scan for codes because you might have a problem beyond the cam position sensor problem.

You do not need a code reader. You use a paper clip to connect the top two pins on the right side of your dashboard diagnostic connector, (ignition on, but engine not running), then count the flashes made by the "check engine" light.

Here's a useful video.
http://www.youtube.com/watch?v=UIKdbTFvyUU

BTW these are terrific cars, especially the sporty SE verson. Roomy, great visibility, nice driving characteristics, reliable and pretty cheap and easy to service and repair.

Biomistake · 10-28-2012, 03:08 PM

Hi there. Thanks for the reply. I did as you said and jumped the terminals just about a half hour ago and here is what was returned:
Code 12
Code 41
Code 42
After scouring the net a bit I saw that code 12 is diagnostic mode. Code 41 is the cam sensor. And code 42 is EST signal did not change.
Code 41 makes sense if it threw the magnet, but I have no idea what would cause the other. Any suggestions?

MagicRat · 10-28-2012, 08:12 PM

CODE 42
Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system. During cranking, the timing is controlled by the ignition module and the ECM grounds the EST line. It expects to see no activity on this line at this time. When the ECM enters EST mode, it applies +5 volts to the BYPASS line and expects to see voltage variations on the EST line.
Reasons for the ECM to set Code 42:
? System in BYPASS mode (i.e. EST line supposedly grounded) but activity sensed on EST line
? System in EST mode (i.e. BYPASS line driven with +5 volts) but no activity seen on the EST line

Possible causes include:
1. BYPASS line is open or grounded
2. EST line is open or grounded
3. Poor connections between ignition module and ECM
4. Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise
5. Faulty or incorrect ignition module
6. Faulty ECM

From:http://www.theimportkiller.com/forum...hp?topic=420.0

Biomistake · 10-28-2012, 09:33 PM

Cool. Thanks for the info on the code 42. I found a test procedure for the ECM and the ICM. The address is http://www.fieros.de/en/v6help/code42.html . I'm going to try it tomorrow after work. I'll post again and let you know what I find. I'll have to acquire a test light first though.

Seems like a good test procedure and a well thought out site. I just hope it's not the ECM thats bad. That will be an expensive fix.
As for the code 41 I'll just have to have the magnetic puck replaced.But also I was reading that it might be possible to replace the magnet by pulling the sensor and j-b welding n aftermarket one in it's place. What do you think if the feasibility of that? Thanks again. All god info..

MagicRat · 10-28-2012, 11:03 PM

Thank you for the update. Let us know how it goes.

Biomistake · 10-29-2012, 06:41 PM

Just so you know I couldn't get ahold of a test light so I'm honda have to make one. I'll probably test it out on friday. I'll let you know what I find.

Biomistake · 10-31-2012, 07:47 PM

Hi again. I got a little antsy today and decided to pull the neg battery cable just to see what happens. So I unhooked it at lunch and left it off till work was over (just over 4 hours). It was still a hard start and wanted to stall untill the temp came up and the check engine light came back on instantly so I didn't hold out much hope. I drive it back home, about 20 miles from work and checked the codes. The code 42 was gone.

Now last night before dark I decided to check my icu just for s&g and saw that my connector was slightly cracked down the center. So I wiggled the wires to be sure they were seated properly. I wiggled the ground wires underneath it also just to be sure. I wonder if that was what did it. I'll never know. All I do know is today it didn't show a code 42. Next up is getting the magnetic puck on the camshaft replaced. That should take care of the 41.

As I said before, I heard someone talk about j-b welding a new magnet I'm place if the thrown one. Anyone tried this? Or does anyone think it's feasable? Magicrat?

MagicRat · 10-31-2012, 09:15 PM

I have not hear of it being done. It would be a fair amount of work to get to it and I am not sure if the end result would justify the effort. If you go for it, get a service manual so you kow how to remove the front cover, etc.

Biomistake · 11-01-2012, 05:57 AM

Yeah, I was planning on buying a chilton manual tomorrow on pay day. But from what I saw they said to remove the cam sensor and I should be able to access the magnetic puck through it's hole without tearing apart the whole engine. . it sounds about right to me because thats how everyone says to check if the magnet is still there or not. I figure since it's a hall effect sensor (a semi-conductor which is tripped by a magnetic field) that the magnets would pass by that hole fairly Its just that the puck is a special order at my local parts store which means it'll take forever to get here and its rapidly getting cold. I'm in MN do the quicker the fix, the better. I'll let you know what I find out.

Biomistake · 11-01-2012, 06:03 AM

Oh and btw, if you want to know what the culprit looks like I went to o'reiley auto parts and had them look it up. Www.oreileyauto.com part number 2-96097 .

Biomistake · 11-01-2012, 07:15 AM

Ok, after a little more searching I found a step by step process on how to replace the magnet without ripping the engine apart. Its at http://padgett.performanceresearch.us/cars/cammag.htm . I ran a google search with the search terms as padgett cam magnet and that site was what was returned. Great pics and ready to follow instructions. Hope this helps someone too. Guess I'm going to order that magnet now. Lol

Tech II · 11-01-2012, 08:33 PM

Have you pulled the cam sensor to see if the magnet is missing?

Biomistake · 11-01-2012, 08:54 PM

Hi Tech II. I have not personally checked to see if the magnet was gone but the guy who gave me the bonneville said his mechanic checked and saw that the magnet was missing. When I try the new magnet j-b weld trick I'm going to replace the sensor anyway wiether its bad or not. I've also heard that even if the magnet isn't there it could have lost its magnetism anyway. But the report I got was that it was inspected and the magnet is gone.

Biomistake · 11-19-2012, 01:16 PM

Ok so heres the scoop guys. On last saturday I followed the step by step process from the website that I posted. I found out that the magnet had been thrown out of the cam sproket. I followed the procedure and j-b welded the new/old magnet back into place (i got a used one from a junk yard from the same make and model). I let the j-b weld cure and put it all back together. Also I cleared the codes before I started it. I have no check engine light on now and no codes. So the process works if anyone is interested.

The idle is smooth now. But it still is rough running when cold. I'm wondering if it's a vacuum issue at this point. I'm thinking maybe egr or iac or fuel regulator. Above have any thoughts on this? Thanks.

POST REPLY TO THIS THREAD