This is my wife's car so I don't drive it much unless something goes wrong of course. It's a 98 Duratec.
A couple of weeks ago she said the power steering would not work and the theft light blinked but after a few seconds everything was fine. So I checked the steering changed the fluid (baster method) and it's been OK since. What she didn't tell me and I found out last night it was stalling loosing power. We were on our way home after dark and the car had been good for around 30min. and than it stalled with no power and all power off but it would start running before it quit. We got home and this happened intermittently all the way. In the driveway I could see the headlights and everything else go on and off but before it quit it would come back. I could also hear the door locks chatter when this was going on.
After reading everything I could find here I think it might be the PCM relay but I never found out if all power would go out if that relay fails only that the car would stall. So before I replace the relay can anybody confirm that this is what will happen.
Battery is new and tests good. Alternator seems to be OK and grounds are clean but I have not checked them very closely yet.
Headlights and door locks are controlled by the GEM, not the PCM. Honestly it sounds like a connection problem, so I would be checking all your battery cables and ground carefully. I would also get the charging system tested at least twice (at different stores) to make sure your battery and alternator are good.
Thanks for your replies. After thinking this over I have to agree it's a ground or + problem. All power is definitely going down when this happens but it's in very short bursts like 1 or 2 seconds. The grounds I know of are the braided one on the firewall to the engine and I just cleaned and made sure it was tight so that one should be OK. The ground from battery to the body looks like new and the one to the block also looks fine. I see no corrosion but that is possible. The positive battery cable looks good but I will check it more closely. The battery is only a few months old and holds a charge quite well. That leaves the alternator and it's 14 years old with almost 160k on it so that may be the problem. Also when I changed the oil pan gasket I could see the alternater was very gunked up and I cleaned the best I could and that may have caused this problem. I have a SnapOn tester for the alternator and it will also do a demand test on the battery so I will check.
My question now is this problem is intermittent and the alternator may show OK so can it be shorting internally to cause this. Also I looked in the topic finder to R&R the alternator on the Duratec but the link didn't work so if you can direct me to a link that does that would be great because I may be doing this soon.
If the alternator drops out, then the battery should be able to handle the loads so the car keeps going. You might notice your lights dim, but everything should not go out completely unless the battery is dead. Make sure you do a load test on the battery and don't just go by the voltage.
I've seen this behavior before when the battery has an internal break or short. When you go over a bump the shock breaks the connection in the battery and everything goes out. How does the battery look inside and/or what is the specific gravity in all the cells?
Thanks Sheila I found the vid and your right it shows what I remember reading on here.
Behlinda I tested the alternator with the SnapOn tool and my digital volt meter and I'm getting 14.74v when I first start and it seems to settle on 14.30v and stays steady. I ran the engine for 15 to 20 min and with the meter I checked at the block, fender and firewall and got no drop in voltage. Also I giggled all the ground and + cables and voltage stayed steady. I have to agree it's a cable and I'm thinking it's the negative battery to fender and block so I will be rebuilding those first than the positive will be next. I will confirm the neg cables have some corrosion and if I opened the cables I'm sure theirs more. This problem has only happened at night and I'm thinking with all the demand on the electrical the ground cable resistance is causing the shutdown. I will do the demand test on the battery but I think it's probably OK.
It will take awhile but I will report back on the results.
Just wanted to let everyone know what I found. I think this will fix the problem but only time will tell. Yes as usual you guys were right as you can see in my not to sharp picture what I found when I removed the ground from the block. The fitting was on the cable but as I was removing it fell off and believe it or not that is the factory cable. Pretty crappy if you ask me. Anyway I replaced the cable with #4 instead of the factory #6 and used a new terminal connector and cleaned everything also rebuilt the pigtail that goes to the fender. Maybe it's just me but it seems to run a little smoother now.