not running on all 8 cyl
 

car was running great up until a couple weeks ago...

Came out of the grocery store - felt like it was running on less than 8 cyl when I cranked it - putted, shook like crazy, low power, sounded like hell. Made it home, popped the hood and poked around-nothing out of the ordinary. Sat for about two weeks until I had time to look at it again.

Yesterday, battery was dead. Jumped it but still ran like it did before. Only work I've done over last month was to change out fuel injectors and last summer TB/WP, new MAF, new cam gears. Part of the poking around was making sure the fi's were still plugged in and hooked up properly.

Have to wait until pay-day to get a new battery. In the meantime, what should I be looking at? Could a dying battery cause it to run like that?

TIA

a bad battery will cause the car to run poorly then the engine will die .

When you get your new battery first put it on a 6 amp charger for 3 hours before you install it.
A trickle charger isnt going to work here.


Then put in the new battery and clean the elex connections while the battery is out.
NOTE make sure the ground strap connection is good,

look at the end of the cable if its corroded then replace it.

Remove both of the coil leads and inspect the ends for corrosion,
and make sure the wires are not rubbing on any part of their run, if a wire id damaged from rubbing then it may need to be replaced.

Check the charging system belt tight and that your getting 13.5 or higher from the alt at 1500RPM
if its less than this with a properly charged battery then the alternator has a bad diode

Disconnect the ground strap and fully charge the battery. Let it sit for half an hour disconnected from the car and charger and measure the voltage at the terminals. Less than 12.5v and I replace the battery.

Sounds similar to what I was experiencing. My fuel filter was shot which made my fuel pump relay run hot and burn out.
I also experienced something fairly similar about a year ago and it was a bad battery

And the second paragraph of your post would make a good rap song. I found myself reading it very rhythmically.

Thank you for the replies.

My neighbor has a charger, so put it on until multi meter read 12.6. Cranked fine but was still missing. Held RPMs at 1500 and slowly everything smoothed out. Turned out the problem is the battery.

Merlin - no corrosion to be found. Will follow your other steps when I get a new battery.

I'll put in a new one next week and should be good to go! Whew. Strange that a bad battery would make it run like that. Thought I'd blown the engine or something.

Hey Camo, put some beats to it and give me 5% of the royalties.

12.6v connected to a charger would be still needing a charge, fully charged while connected is over 13v. If that is what it read disconnected from the charger then the battery sounds fine, and trouble is likely something else.

If confused on this, take the battery to a store that can charge and test it.

My experience w '86
 

attery. Factory manual says remove the alternator. I just unwired it, the car ran normal, supposed to be the alternator. Swapped on one from my other 928, still ran crappy but the "good" car didn't run crappy w the alt fr the bad car. That sorta indicated a wore prob. Couldn't find it, my son paid a local mechanic a bundle of cash n I never saw a note telling what it was exactly. I know he charged like he'd done everything on the list I had given him outlining everything I'd done including a new timing belt service :-(.

got the new battery in tonight, and it cranked and ran like a top.

However, another issue has joined the party: Cranks fine cold, but going to the store and trying to start still warm - revs to 2500 RPM then tries to die. If I give some gas to keep from dying, revs back up, and the dance begins. If I can hold the gas peddle and maintain steady revs this all lasts about 45 seconds. If not, it's rev-die crank -rev-die, and so on.

I guess some sort of sensor- one of the temps? Going to search now...

I keep seeing the S4's having issues with their Crank Position Sensors. I don't own an S4, but it would be part of my spares for troubleshooting. Temp II Sensor comes to mind as well.

I would also replace the main ground strap. Mine looked fine but the inside of the one end that attaches to the frame was all corroded inside. You can only see this if you open it up. You can get a new replacement for $42.