Bouncing timing mark

[ChrisCraftFan]

Still struggling on my 2000 VP 5.7 gsi pefs. Finally got the correct injectors and seem to have resolved my rich condition. Now when I set the timing with the jumper it seems to search a little for idle and the timing mark moves a little back and forth. When I pull out the jumper and bring to 1000 rpm manually it seems much smoother. Any thoughts on what to look at? I have previously replaced plugs, wires (tested each wire as well) new cap and rotor. The marina put in a new ignition coil and ignition module recently as well. (Maybe have 4 hours on them) wondering if since it was running rich (Black smoke and hesitation on acceleration) could it just be a little "carboned up"? Now that I seem to have that resolved that maybe run it out on the water a bit? (wishful thinking I know)

 

[dubs283]

the service/timing tool should lock the timing into base mode so it wont advance. with the service tool attached run the engine to 1000-1200 rpm, timing should hold steady allowing you to set properly

 

[ChrisCraftFan]

that's correct but unfortunately it doesn't' hold steady in base mode. I used this same procedure last year and worked great.

 

[dubs283]

unfortunately it doesn't' hold steady in base mode.

you mentioned in your op that it was at idle in base mode?

throttling up is required, sometimes higher than 1200 but no more than 1500 rpm

did you replace the plugs, cap and rotor?

 

[ChrisCraftFan]

yes I did replace. The Cap and rotor have about 30 minutes on them, however the plugs are still the ones that I had in there when it was running rich. I had them out and they were a little black but nothing major that I could tell. Just a little black soot. I tested all the wires and they all have the same ohms per foot. When I put the jumper in it increase the idle to around 1000. However, this time it seems to be searching for steady idle and is varying a bit maybe 1000-1200 back and forth along with the timing mark. if I remove the jumper and bring it to 1100 rpm manually is is much smoother.

 

[dubs283]

ohms testing of the wires is okay, it's better to do a kv test - this will tell you what voltage is actually travelling along the wire, it can change with load, heat, rpm, age of wires, etc...

fouled plugs are just that, fouled. there's no way to get them back to original or good, you're best to replace them

i understand fully what you are experiencing, the jumper automatically bumps up rpm and the timing is waffling, got it from your previous posts

try advancing the throttle with the timing tool in place - no need to go more than 1500 rpm, it may help steady the timing