engine cutting out
 

Hey everyone, on my 91 olds toronado 3.8 240,000 miles
at any speed and in any gear I will be driving along and all of a sudden the engine will cut out. when it does this it is quick and the tach drops down. Just as fast it jumps back up and the engine runs fine. when the tach jumps back up there is a bang as if the tranny was slipping and then caught back into gear. it does this mostly at light peddle pressure. if I'm accelerating with the peddle more than 25% pressed it won't do it. I would think it's the tranny but it's odd that the tach drops. I'll be at 2000 rpm and all of a sudden it does it and the tach drops to about 1000 instantly, then just as fast jumps back up to 2000 and bangs. I feel the bang more than hear it. it also sounds like the engine quits when it is doing this. it happens so fast i don't even have time to take my foot off the gas.
ANY ideas would be appreciated! I'm at a loss, it's been doing this for months.

Off the top of my head: I'm guessing there is a loose connection somewhere, probably a ground. Engine moves around just right and the ground path becomes compromised, cutting power to the PCM which would cut power to the ignition and transmission solenoids.

I'd check wiring, starting at the battery terminals.

Thanks, I'll check them Monday.

checked all my grounds, except for the one under the back seat and it only grounds the tail lights I think. all were clean and tight.
Is it possible for the crank sensor to cause this? the reason I ask is because of the tach dropping down when the cut out happens.
I'm also going to check my PCM wiring as soon as I get a chance, I had it and BCM and HVAC controller out recently to fix something else.
thanks for the help, I am stuck as of now and am grasping at straws.

If you ran through slush and got some on that hot sensor it will crate problems.

It could be the crank sensor. I'd maybe look at the crank sensor next.

gee, can't wait to take my harmonic balancer off! LOL. how do you all align the sensor? I've just kinda eyed it up in the past and it's been ok until now. if that is even the problem.
Would the problem I'm having set a code? I checked and have no codes present or in history.
a new alignment tool is $600 to $700. I found one one ebay for $152.

haven't driven it in snow or slush. I replaced the connector on it last year. I'll pull it off and take a look.

I had this engine wrong. The slush is more with the 3.1 and 2.8 which have the sensor going into the block. I have the info on your vehicle. We would normally scope the crank signal and see if it's good coming out of the sensor and then into the module. If good going into the module you can be sure the module is bad. Knowing this engine I think the module is the most likely candidate.
Here's some info on the crank sensor.

https://cimg9.ibsrv.net/gimg/www.gmf...c8af19608f.jpg
https://cimg1.ibsrv.net/gimg/www.gmf...01a21ac70b.jpg

yeah I remembered after I posted that it has a plastic cover over it to protect from snow, water etc.
the biggest problem I have in testing voltage etc is it's intermittent and only does it when driving.
but I do have a known good spare module, I think I'll swap it out.
Thanks for info.