(Update: fixed) 97 Bonneville 3.8L stalling - was crank sens
 

Resolution; I was desperate to get this fixed since I was under pressure to do something. The three leading possible causes were battery cable corrosion, crank sensor, or PCM. There was some corrosion on a battery cable (which has now been cleaned up) but I'm dismissing this as a cause since the stalling predated the last battery replacement/service in the fall. I used a hair dryer on the PCM to see if heat would cause the stall. It didn't (though maybe I needed more heat), so I went ahead and had the crank sensor replaced. It had been stalling several times a day (and getting worse) and now has gone three days with no stalling, so is apparently fixed. Thanks guys!

Original posting;
Hello - My daughters 97 Bonneville has 120k miles and since we bought it used last summer it has stalled occasionally with no codes - but more frequently lately. It might stall several times in a week, or go weeks in-between. I replaced plugs and wires to get rid of an ignition code, and while it runs great it still stalls. After replacing the fuel filter it went two months (over the winter) without stalling, but not sure if it was luck, the temperature, or the filter. IWhen it first started occurring, she could start it right back up but now it just cranks and won't restart for about 5 minutes. Someone suggested the catalytic converter but an exhaust guy told me that it would be throwing a code and would not have much power. She has commented that sometimes when it starts to die, she can hit the gas and keep it going. It did stumble once for me on the interstate but never died. I really need to get this addressed as it is a safety concern - stalling in traffic. So - what can cause warm stalling, throws no codes, and has to sit for five minutes before restarting? I searched the forums and there are a lot of ideas, but all seem to throw codes. What should I check/replace first? Thanks!

Hi Tom..

First thing to do is find out if it has spark and fuel pressure when it won't start.

The issue is going to be one or the other and the cause could vary greatly. Do you have a fuel pressure gauge and the ability to have the car repeat the issue when you have the time to test?

If so..I'd check pressure w/o running when cold, ensure it stays at that pressure for 10mins. Then warm it up and do the same.

Have you been using much coolant lately?

I have the car today to play with - normally I am working or she is working. It has never done it for me but I can drive it for a while and see what happens. Perhaps I can rig something up to show her if there is spark when it happens. I don't have a fuel pressure gauge - would need to pick one up.

Nope - not using any coolant - just checked the other day.

I'd hit the parts store and spend about $30-$40

Get an fuel pressure tester and they usually have a little inline spark checker. Put that in line so you don't need to think about it..and hook up the tester once it stalls..then cycle the key on and off a few times w/o starting.. anything under 30lbs of pressure and you probably can't start it.

After checking for spark and fuel pressure, as Bill and Bill have suggested, there are a couple of other components to check that can cause random stalling. One is dirty or corroded battery cables and ground connections. (The ends of the cables need to be removed and the insulation peeled back to properly inspect.) The other is a bad PCM (engine control computer).

Crankshaft position sensor. Next time it wont fire off, spil some water on the crank sensor (located to the right of the harmonic balancer) Then see if it starts. With age, these will go bad when heated up during normal use. They will also have a "burnt, electrical" smell when bad.
Attachment 50817

Yes... CPS is also a good one. Learned something new with the water test. ;) Thanks

How hard to replace?
 

How hard is a CPS to replace? Will it throw codes when failing? Thanks!