Ignition timing jumps around.

[Mogordo]

Hi, Have any of you had experience with ignition timing "jumping around"? Meaning the mark goes all over the place. This is happening on my '83 Sentra. It will go from something like 90 degrees BTDC to something like 15 ATDC and all over in between. My dad suggested the number one cylinder could be misfiring. I think I tried putting the timing light clamp on the number four and it did the same thing but I am not sure. I used the same light for the Tercel and that had normal, steady readings so I don't think it's the light.
Thanks for any ideas. The car has been going like this a while but it would be helpful to figure it out and fix what is causing it if it isn't very involved.
Cari

[rer233]

Loose crankshaft pulley??

[Mogordo]

I should probably check. With tension on everything it doesn't look like it's loose but maybe the tension makes it look fine when it isn't. That happened before but it really shouldn't be loose now because I put medium threadlocker on it and torqued it to specification. But the issues stemming from it loose before were quite inconvenient so I should really check.

[Mogordo]

Fortunately that bolt still feels tight.

[NWMO]

Mogordo,

Many crankshaft pulleys are two part units with a layer of rubber sandwiched in between. Sometimes they will allow the outer piece to spin on the inner piece and then the TDC mark goes out the window and is always “moving”. Get #1 to TDC by pulling the plug and visually inspecting. Once there, check your pulley mark and see if it’s still good.

Chris

[dlb]

Many crankshaft pulleys are two part units with a layer of rubber sandwiched in between. Sometimes they will allow the outer piece to spin on the inner piece and then the TDC mark goes out the window and is always “moving”.

+1

My other thought is the spark plug wires are faulty. I once had a VW Fox that ran like piss. One night with the hood open while it was acting up I saw sparks jumping around between each of the wires. If I had put a timing light on it then I bet I would have seen the timing mark jumping around like yours. So if you haven't replaced those lately, that's another thing I would consider.

[atoyta]

I have had a worn out timing chain or belt cause this. I also had a worn out distributor cause the same thing.

[Mogordo]

Thanks everbody! I had this car pretty apart after the crankshaft bolt came loose over a year ago and got jammed and broke off when I tried to remove it. We managed to get it drilled and cleaned out without ruining the threads but I had to get a new (old) pulley so I know this one sure looks like a single piece.
I also put a new timing belt on it when I finally put it back together. The tensioner that came with the belt had gotten bent in the box so I did re-use the old one but that one had only been on the car a couple months so I figured it was probably fine. I wondered about the distributor too. I don't know too much about components of it that could get worn or become faulty. I checked the shaft and didn't find any side-to-side play, just a little rotational and in-and-out which from my reading I think is normal. Spark plug wires crossed my mind too. I had replaced these as I recall within a few months prior to it sitting for close to a year while I figured out the crankshaft stuff but that doesn't mean they are good. They are Bosch from RockAuto and I think they came looking like they had been around a while. I checked the spark plugs themselves and they all looked normally lightly worn so that's good. Spark plug wires typically are pretty cheap so I might end up trying another set.
Thanks again, if anyone has further ideas or knows more about checking the distributor I'd like to hear more.
Cari