95 Riviera stalls randomly

Hello everyone. I have been on this site ever since I got my Riviera this past December. This site has been great and I have received tons of info from here. I have searched and searched and have not found an answer for my current problem.
I have a 95 Riviera with the supercharged engine. The engine started stalling at stoplights and turns and it would always start up immediately. I pulled the codes and it read EGR valve and Cam sensor so I replaced them both. After that the problem was still there. I then replaced plugs and wires, SC coupler, removed and cleaned throttle body, and replaced the crankshaft sensor. It still dies but not nearly as much. Only once or twice a day and not every day. One thing I noticed now that I have a voltmeter installed is that when it gets ready to stall, the voltage drops from 14.0 volts to 12.8. Then the rpms drop. Sometimes the rpms will drop and return to normal without stalling.
I guess my question is, could my alternator be the culprit? If not, what else could it be? Please help!

One more thing to add. There are currently no SES lights or codes. Thanks!

consider possibility of a worn ignition switch

check your crank position sensor going thru that problem my self .... is it hard to start?

I changed the crank position sensor already. Its not hard to start at all. Starts right up every time. Yesterday it cut off again and triggered the SES light. When I pulled the codes they were P0122- TPS low input, P0573 high voltage at brake switch, and P0630 that said low battery voltage. I cleared the codes and they have not come back yet. Any clues?

albertj wrote:

consider possibility of a worn ignition switch

How many miles on the car? Possibly ignition switch, but my 1st guess would be MAF sensor. Spray some sensor clean into your TB, and see if anything changes. I would suspect the voltage drop as a sign of IGN switch but it could be dropping because the engine is already in the process of stalling. Being that you've already changed the Crank, and cam sensors I would go ahead and rule those out (there always a chance but I doubt it). Check for vacuum leaks in the lines as well as the LIM, these would also cause you grief. Do a load test on your battery also, just to make sure.

It has about 90,000 miles on it. The ignition switch is on my list of repairs needed since I have a VATS problem and I learned on here that the ignition switch wiring could be the problem. I didn't think it could cause this problem as well. I already changed all the vacuum lines and repaired the supercharger coupler so it has a new gasket. I will check the MAF sensor first. Thanks!

artlock wrote:

I already changed all the vacuum lines and repaired the supercharger coupler so it has a new gasket. I will check the MAF sensor first. Thanks!

Your probably just talking about the upper intake gasket though right? I suggest checking for leaks in your Lower intake gasket. If your intake is leaking its going to run like a turd. Easy way is, believe it or not, with a simple garden hose. Run water over the LIM while running the car just move the stream around so you know you covered all exposed area's, or anywhere 2 surfaces meet and you'll know tight away if its that or not by the way the car idles. Just another suggestion.

Cool thanks. I'll try that too!

You may also want to double check all major electrical connection points - clean major grounds, confirm battery cables clean and tight at all posts along the way from battery to underhood jump block to starter, alternator charging post tight, etc etc...

OK, I did the water test and no change in idle. I cleaned the maf sensor as well. I did notice a vacuum hose that connected to a big plastic box on the firewall that was dry rotted and sucked flat so I replaced it. Could that have been the problem? And what is that box for?

More than a year later and the problem is finally solved! The only things I hadn't checked was the ignition switch and fuel pump. While testing the fuel pump and subsequently the fuel pressure regulator, it was determined that the hose on the pressure regulator was slightly to big, causing a leak. I replaced the hose with the correct one and the fuel pressure was correct. The car ran like crap the rest of the day but the next day and all week it has not cut off once and has been running a lot better.
i don't know why it got worse before it got better but I am glad it's not cutting off anymore! Thanks everyone!

Perhaps the ecu just needed to get used to the correct fuel pressure again.

RidzRiv wrote:

Perhaps the ecu just needed to get used to the correct fuel pressure again.

most likely... ECU was probably commanding the fuel pump to flood the engine, we should asked about a sulfur smell...

I missed this thread originally. Reading through I kept thinking "fuel pump". Glad you found a potential fix with the hose, but if this continues, particularly if the car won't restart sometimes, you'll need to replace the fuel sending unit (pump). It's not difficult, and we have a write-up.

My issue started exactly like yours and progressed until the pump needed replaced. If yours acts up again and won't restart, listen for the pump in the rear with key on. If no sound, try tapping the trunk floor with a flashlight or other heavy object. This is how I diagnosed mine. Good luck.

That makes sense about the ecu. Hopefully, this problem is closed. I have another question. Now there is a slight hesitation when I accelerate from a stand still. I am assuming spark plugs but I changed them about a year ago. Could the year long vacuum leak cause the spark plugs to go bad in a year?

I would assume wires before plugs, since you replaced the plugs recently.

I replaced the wires the same time I replaced the plugs.

artlock wrote:

I replaced the wires the same time I replaced the plugs.

Yes but with what? The SC Riv has a high energy ignition system and will fry wires in a blink. I use Magnecor wires. Others use OE wires (actually the OE wires are good but don't last but so long, 50-75k miles ish).

You would def noT be the first person on here to put on a new set of say Brand name wires and have them turn out to be inadequate. I

I used a set of AC Delco wires. Are those good or should I get a set of the Magnacor wires?

artlock wrote:

I used a set of AC Delco wires. Are those good or should I get a set of the Magnacor wires?

The delco wires should be fine, but do take the time for a visual inspection. Get a flashlight and look inside the boots at both ends of each wire for a center conductor that got cut at the crimp. It will look like the center core is not clamped into the terminal. Also, do you have any check engine codes set at the moment?

artlock wrote:

I used a set of AC Delco wires. Are those good or should I get a set of the Magnacor wires?

also check your fuel pump.the OE fuel pump can soldier on forever!even with fragged interior,making all kinds of problems If the in tank filter is shot or torn the pump is gone.

I currently do not have any check engine codes. I actually replaced plugs and wires today. I was just planning on replacing the plugs but two of the wires broke as I was removing them so I went on and grabbed another set of ac delco wires. It is running better. The old plugs gap was almost .070. I will take a look inside of the wires tomorrow.

How do I check the fuel pump? I checked the pressure and KOEO it was right at 41 psi. When I started the engine it dropped to about 35 psi. According to the boot it is good but just barely. Is there another check I can do?

Those fuel PSI readings are normal, but failing fuel pumps can be 100% one minute and 0% the next. This would be causing your stall, but not the hesitation. Hesitation is more likely ignition related. Hope the new wires and plugs fixed it. .070" is pretty worn. Neither the fuel pump or weak ignition components are likely to throw a code until they get really bad.

artlock wrote:

I currently do not have any check engine codes. I actually replaced plugs and wires today. I was just planning on replacing the plugs but two of the wires broke as I was removing them so I went on and grabbed another set of ac delco wires. It is running better. The old plugs gap was almost .070. I will take a look inside of the wires tomorrow.

How do I check the fuel pump? I checked the pressure and KOEO it was right at 41 psi. When I started the engine it dropped to about 35 psi. According to the boot it is good but just barely. Is there another check I can do?

To check the pump you have to access it from the trunk. do you have an FSM? you need one. It's a small tin of worms getting the fuel pump out if you live in the rust belt from pics I've seen.Be prepared to install a new fuel pump lock ring I think.