Hard stumble/stutter and stalling

[fastflask95]

Welp, I don't know where to start. I replaced my battery about a month ago since the old one was about 10 years old and it was getting weak. Living in Ohio, I figured I better replace it now before it left me stranded in the cold. Well, about a week or two after having that done, my car developed a new problem where it stutters/stumbles at random and at any speed, and it will also stall at low speeds and slow turning.No amount of giving it gas clears it up, I pretty much have to wait for it to pass. I replaced the maf sensor about a year ago, and I swapped out the throttle position sensor to try to narrow down some things. When it stumbles, the RPM's jump around by about 500/1000 and the volts will drop to about 12v and once it stops stuttering it comes back up. The thing that really drives me crazy is that it doesn't throw a code, I've been dealing with this for about 3 weeks and I haven't had my CEL come on once. I tried to have my mechanic look at it but it was one of those days where it wanted to act fine and since there is no CEL, there's not much he could look for. So any insight into this would be extremely appreciated!

Also, I was able to get a short video of it acting up today and you can hear a slight clunking noise when it stumbles. But pay close attention to the Tach and Volt meter.
https://www.youtube.com/watch?v=s6p4Op_ ... e=youtu.be

[96 SSEi]

hi, unplug the maf - aftermarket units are known to die quick - mine lasted a year = if only to eliminate.

see if that helps

[fastflask95]

Tried that already, should have included that in the original post. My bad.

[96 SSEi]

ok, I would next check the battery and alternator wires for corrosion and good contact to terminals.

[MKMike]

The problem appears to be electrical, rather than fuel related.
Electrical issues do all sorts of weird things to the way a vehicle operates.

The very first thing I'd check is that the battery connections are both tight and clean.
If they are clean and snug, have the battery tested.
It could be a defective battery.
If that checks out, I would suspect the alternator is going bad.

[nos4blood70]

This sounds like a crank position sensor.

[fastflask95]

Alright, I'll check all the electrical connections when I get off work in the morning. Working midnights makes it hard to fit sleep, car troubles, and running errands into one day.

Also, there was a bit of corrosion when I changed the battery so I'll definitely try to clean it up even better.

[fastflask95]

Alright, so I took some time and thoroughly cleaned the battery terminals and connectors, the positive was pretty bad after checking closely. I checked the connections under the hood and to the alternator and they all look reasonably fine. I'll have to see if it acts up here in the next couple days.

I also forgot to mention that I did have an amplifier hooked up for a little while but have since removed it. Do you guys think this could have weakened/damaged my alternator?

[MKMike]

I suppose it's possible but, realistically, at 143,000 miles, the alternator is nearing the end of its useful life, anyway.
The electrical issues most likely stem from the corrosion on the cable ends.
You should pull off the cover off the end of the cable to see if there's more corrosion underneath.

[fastflask95]

Alright, Sorry it took so long to reply back.

So I checked all my connections and everything is good, I've checked and double checked. I took it to my mechanic and he ran a scan tool to see if he could find anything. I had a code for the crank sensor and a couple of ignition codes (he said that these were probably in there because my battery died). So I had him replace the sensor and after I got my car back, it's still doing it. I took it back to him and he tested fuel pressure and the resistance of my coils and everything is with-in spec. I honestly don't believe it's a fuel problem because when it cuts in and out, it's a hard cut not like a sputter. I did notice when I picked it up the first time after he replaced the Crank sensor, my voltage was lower than normal. Usually it sits around the 14.5-14.7 range on the voltmeter in the car but when i picked it up, it was hovering below the 14 mark. It has since gone back to normal.

I replaced my MAF about a year about with a new Hitachi one so I don't think it's that either.

I also had my battery and alternator tested good. But is it possible that the alternator tested good then but still act up intermittently causing it too look like it's good when it's really not?

[fastflask95]

I know this thread is dead but I figure I'd post my solution for anyone that has similar problems and can't figure it out.

My problem had disappeared for a couple month's and then the day after christmas I went to leave work and my car wouldn't stay running, stumble and stall out almost immediately when put into gear. So I had it towed to the shop.

Well it turns out that my upper intake manifold went bad.

[MKMike]

Thanks for posting the actual cause of the problem.
Often, people search the forum looking for answers and--even if they never post about it--they're helped when they find resolutions to problems.
Even for the forum veterans, it's always good to know what solves the problem, especially when the "symptoms" are unusual.