95 lumina missing, shutting off intermittently.

Trying to figure out what is most likely the cause of the following symptoms to get wife's car running reliably again. It's a 95 model with 3.1 liter v6.

1 - MOST days, it runs perfectly without a problem whatsoever.

2 - OTHER days it may miss or "bump" at any speed intermittently while driving.

3 - TWICE it has just up and died on her while sitting at a stop sign, won't crank right back up but if it sits a few minutes it will crank up and may run fine for a few days.

4 - TODAY she says she was doing 15-20 mph in a subdivision and it started "chugging" and when she gassed it, it went on until she was back up to highway speed and it "bumped" again a few times but made it home.

I'm leaning towards the crank sensor(s) because I am not getting any codes to pop up BUT when I look up crank sensor for this car it shows one to be behind the main crank pulley and one on the rear of the engine below center of exhaust header. From what I can see BOTH of them will be a pain in the rear to change to say the least so that is why I am asking if something else can cause this before I go through all the trouble to change them, OR is one more likely to fail than the other and should be changed first?

I would check fuel pressure first, also the ign module is another possibility, Because of the possibility the sensor on the rear of the block will not come out without braking off, I would eliminate the other possibilities or check them out first.

If you do the crankcase sensor, soak the hell out of it with PB blaster or something like, both before and after removing the retainer bolt(s), and give it time to soak in...it may help it come out without breaking off.

If you have the one behind the crank pulley, make sure the wiring has not broken out of the retainer and is rubbing the pulley...happens sometimes, gives intermittent problems like this...

I went out and looked and I do see what I believe to be at least one bolt holding what I believe to be the crank sensor. It is all so caked up with oil residue that it is very hard to see and it appears to have 3 wires coming out from it in a sleeve that run over by the oil filter to a plug in. Is that the only crank sensor or does this car possibly have the other one on the back side of the motor too because I climbed under there and I couldn't find it if it is. Before I change the one by the pulley though, what is the best cleaner to use to get all the grime off that wont hurt the wiring so I can inspect it better and have a clean area to mount the new one?

Most any good quality degreaser will do the job.

if not cps my son had had one and it was hard on coil pack and module most time it would be in the coil pack but this does sound like the cps.

good luck...

Sorry, but I forgot to come back and post the outcome. I decided it was too risky to try to change the one sensor and instead of replacing the one by the pulley I just cleaned the heck out of it. It was so gunked up from all the oil changes over the years that I could barely even see the connector. Since I cleaned it, the problem has never come back so I hope that was it.

close up of the crank sensor on the side of the engine (facing the firewall)

http://www.automotiveforums.com/vbulletin/attachment.php?attachmentid=38653&d=1269150248

10mm. someone with small arms can reach around the altenator and get to it, by feel.