DATeem

I have a new to me 98 convertible, L98. No history and from all appearances neglected maintenance. Typical electrical gremlins in the climate control but other than that it has been starting and running fine- ok power and starts right up. Appears to have a new alternator and belts. I am figuring a plugs/wires/cap rotor are in order.
On the way home I turned on the headlights and the radio went off. Turned off headlights and back on and radio back on. Did this a couple of times and headlights opened up normally but every other time the radio would go off and the climate control would flicker. A few miles later and it seemed the engine was starting to run a little rough.
A few more miles and I noticed the amp meter was showing 7.7 volts. The engine began running a little rougher on acceleration.
By now I am crossing my fingers to make another three miles to home. Now the engine is starting to run really rough, no acceleration and starting to spit, sputter and backfire. Headlights are off as is radio. One mile to go and it is so rough I am only at 35 mph with backfires consistent. Half a mile and down to 20 mph, just hoping. Now down to 10 mph and really jerking and backfiring. Three blocks from home it died and I coasted into my driveway-thankfully.
When I checked under the hood I noticed a vacuum line on the left inner fender well that was deteriorated and broken. Nothing else obvious. Belts are good etc.
Tonight I put a charger on it and voltage shows 11.7. Ran two charge cycles and still the same.
Question: Any potential relationship between vacuum hose and sputtering? I am guessing yes. Coincidence of alternator or battery failure? Any relationship to sputtering and battery/alternator?
I picked up a new vacuum hose but have not installed it yet. I am open to suggestions on where to start and if this is an indication of something more. Thanks for the input.

don hall

Let's start with some clarification. A "98 convertible, L98"?

1998 would be a C5. Maybe a 1988?

WW7

If the battery won't take a charge then you have a bad battery.The reason your car got worse the farther you drove is because the car was running directly off the battery, and the lower the voltage got, the worse it ran until it died.. The vaccuam hose needs to be repaired because it will cause surging.. Then you have to figure out why your alternator isn't charging .You will have alot of testing to do to figure all this out....With a car having that many problems you will need a "factory service manual" with the electrical diagrams..Good Luck...WW

DATeem

Sorry, dyslexic typing. It is a 1989.

Will start with the vacuum cause that is easy. Will pull the unhook the battery to see if it will charge and replace if bad. If battery charges and holds I can start it and look at volt meter in car but beyond that I may have to get some help. I am looking for a shop manual to order. It has been many, many years since I have wrenched on a car. Kind of looking forward to messing about.

aminnich

First check should be the alternator connections and the alternator itself. Then a battery check.

John A. Marker

If your charging system showed 7.7 volts....pull off the alternator and have that checked. Remove the battery and take that with you and have that checked at the same time. If after charging the battery was only at 11.7 volts, you might have a bad cell that is contributing to your issue.

xrav22

You should of had a alternator warning, I believe it is out, as the OP said it stopped charging everything goes wacky as it drains down.
The battery has taken severe abuse from the total draindown, I would change it just in case if you can or check water level and put a charge on it.
Good luck

DATeem

Fixed the vacuum hose and began to pull the battery. As soon as I started to loosen the negative lead, buzzing and electrics came to life. The lead was firm tight but apparently had some corrosion between it and the battery. I put a volt meter to the battery and got 12v. Went ahead and removed the battery, just cause I wanted to learn how, cleaned and checked fluid then loosened connection and used corrosion x on the red leads behind the battery. Put a charge on the battery just to be sure, installed battery back and started right up. I put a volt meter on the battery and was getting 11-12 volts at high idle. Put the volt meter on the alternator and got 11 volts max, then down to 10 when the motor started running a little rough so I shut it down.
So, I pulled the alternator to have it tested and expect to replace it.

DATeem

Yep, bad alternator. Was a re-manufactured from NAPA, looked to be a year or so old. Had an auto/electric shop test it and they said it had an intermittent problem. They are going to build me one over the weekend for only about $40.00 more than the re-manufactured units cost at O'Riellys. I am running the battery through a reconditioning cycle now and they will test it when I go in to pick up the alternator. Thanks for all the advice and direction from those who chipped in.

DATeem

Back on the road! Battery checked out, alternator rebuilt and installed thanks to YouTube video's (I would have never figured out the lower cowl bolt on the side panel). Started right up and voltage stayed at 13.7 consistently. Headlights and systems all go. While looking at connections and wiring I did find the positive battery wire had a large nick in the sheathing where it passed over the steering knuckle. I put some tape over it until getting a drier day to put some shrink tube on it. After finishing putting it back together my shop manual arrived by FedEx. Go figure. First time working on any of my cars in quite a long time and found it a lot of fun.