92 Lesabre backfires, dies, restarts at random

[Andreas E.]

Hi all!

I had described my issue here before, but I think it was buried (as someone had dug up an old post...)

Anyway, for about two weeks now, I get in my 92 Lesabre, 164k miles and it starts just fine. I can drive it for 30 minutes to an hour, then it starts missing, backfiring, and then just dies. Sometimes, when I go fast enough, I guess the torque converter does what a clutch would do in a stick shift and bring the engine back to life, but only under protest. Sometimes the symptoms then go away and reappear a while later. This has happened in hot and cool weather, wet and dry, under normal freeway cruising (hardly a load) and climbing steep hills. There is no rhyme or reason.

Today was the worst of all. Most of my driving was rural two-lane roads, and the engine just quit. Before, it would start right up again, but this time it would not. It just cranked without the engine starting. After a couple of minutes it would start up again. Then it would run fine again as if nothing happened, only to repeat the whole process again.

I have browsed the Buick forums for possible answers. Here's what I have done/checked:

1. replaced fuel filter (since at first it only happens after a fair amount of time)
2. Checked battery terminals for corrosion - they're fine.
3. Checked spark plugs (NGK), normal wear for about 6 months old. Wires were replaced at the same time. The connectors to the coil pack and plugs all seem to be ok. (But the wires were pretty hot, not sure if this is normal.)

I keep running across the camshaft magnet issue. I'd like to see if that's the issue, but the links I've seen are either dead or the websites have been changed to a different subject.

Besides the camshaft magnet, what else could I be looking for? The fuel pump is about 36k miles old. It was replaced before I bought the car a few years ago. The check engine light flashes irregularly when the engine sputters and backfires, but I don't have the ALDL scantool to pull any codes. The paperclip trick will not work as no terminal B. I don't know where to start. Any ideas? Any help is greatly appreciated.

[CL8]

Go to an auto parts store or a mechanic and have them read the codes.

Maybe the fuel pump installed was defective.

[HotZ28]

Terminal "B" is the diagnostic terminal and if you don't have a terminal in that port, nobody can retrieve the codes, even with a scanner. I wonder if the wire/pin have been dislodged from the ALDL terminal? If the cam shaft magnet were broken or missing, it would not cause the engine to stall; however, it will cause stumbling during acceleration off idle, so this is not the problem!

Check for spark & fuel pressure the next time it stalls, more than likely you are missing one, or the other. With the symptoms you mentioned, I would first suspect the crank position sensor (CKPS) and then the ignition control module (ICM).

[Andreas E.]

Thanks for your responses. As far as the B terminal on the ALDL goes, the Haynes manual says that some models may not have this pin.

I will check for spark and fuel pressure. Then do the CKPS. Pardon my ignorance, but is the ICM the same as the coil pack? Or is this one of the many computers.

I have been wondering if it's the fuel pump, as it gets noisier the emptier the tank gets... it's lasted 36k miles, though...

[HotZ28]

If you have the Delco ICM, it would have three coils mounted on top of the ICM. If you have the Magnavox, the coils are incorporated within; so therefore the term "coil pack" is used by some to describe the ICM/Coils.

Delco ICM with MSD coils shown below:

[Andreas E.]

I attached a picture of the engine and coil pack. The second one is of my baby... who could replace this beauty in white and burgundy with anything else...

[Andreas E.]

HotZ28, do the MSD coils make a big difference over the AC Delcos?

[HotZ28]

Yes, if you consider the 92 coil voltage output, but if you use the 97-up coils, there is very little difference. Typically, the MSD coils have less resistance on both the primary and secondary side and they produce more output voltage than OEM coils. (44,000v),

[eaglebreath]

have you had your catilytic converter checked...........they will clog and cause
the engine to stall .

[Andreas E.]

No, the catalytic converter never dawned on me. But you are absolutely right. I once owned an 88 Ford Festiva (don't ask ) where this happened. However, it also would not pass emissions testing, and on my Lesabre it's been passing with flying colors all these years, last time in October 08. I'll give it a couple of taps to see if there is any loose material in it.

[Andreas E.]

I was wondering: where does the tachometer get its signal? From the ICM or the CKPS? Reason I am asking is that by belle left me stranded by the roadside again today, and this time it took it forever to come back to life. While I was cranking, some of the other gauges came to life (such as oil pressue), but the tach was just sitting there, even though the engine was turning. Just trying to pinpoint the cause before I tear down to get to the CKPS. The other thing I have noticed, is that it dies when the temp gets to 200 or above, especially after sitting at a light in 5 o'clock traffic.

[HotZ28]

Normally, if you have no RPM on the tach, the CKPS is not delivering the signal to the ICM. The white wire on the ICM feeds the tach. Time to change the crank position sensor! BTW, the catalytic converter will not cause random stalling, especially heat related!

[Andreas E.]

Dang...

[Andreas E.]

HotZ28, you're the best! Thanks for all your help in pinning down the cause of my belle's demise. Well, she's back to life.

I did replace the crankshaft position sensor, and so far so good! But what a pain!

If anyone else needs to replace this sensor, here a few tips:

Borrow or rent an electric or pneumatic impact wrench. ($18 for 24hrs at "my" hardware store.) You can save yourself hours of cussing, sweating and cuts and bruises. (It's a good workout, though.) You'll need an impact socket as well, 24mm or 15/16 in.

Borrow or rent a real crankshaft pulley puller. Don't buy the cheap kind. Make sure the big long screw you will turn to push the pulley out is at least 6 in long, and you have the correct size impact socket for it as well. You will also need 3 1/4-28 x 3 bolts and washers.

If you have the plastic shroud around the inside of the pulley, there are three fasteners. It is not screwed on. Rather you can pop it off with a screwdriver, or you may need to open the "clamps" first. To get the two studs out, you will need a deep socket 1/2in or 13mm driver.

You do not need to loosen the 8 (or 9?)mm bolt that tightens the sensor to the sensor bracket yet. Once you have the two bolts off, you will have to twist the bracket off of a center prong. I reused my old bracket, as the hole for this prong seemed too small on the new bracket.

As far as the sensor alignment goes, I could not see well, so I measured from the inside of the spindle part that connects to the crankshaft to the outside of the first vane. I think it was 36.5mm, if I remember correctly. Per the instructions that came with the new sensor, the air gap between vane and sensor is supposed to be 0.03 in or 1mm. So I added 1mm to the above number and made the distance from the outside of the crankshaft spindle sticking out of the engine to the outside of the first of the three sensor vanes 37.5mm.

I tightened the crankshaft pulley bolt down, torqued it to 110 lbs-ft per the manual - this time I did need an assistant to stick a screwdriver in the toothed wheel towards the driver's side as I did not want to cause any damage with the impact wrench.

But the serpentine belt back on and she fired right up! Yeah!

Put the rest together and went for a half hour test drive. She purrs like a kitten (that has a Magnaflow dual exhaust meant for a Camaro stuck in its butt.)

Thanks again for all your troubleshooting help!