Romac balancer spun? Can't be...?

So here is the current situation and history...

1. Took car out today on a 40 mile trip to burn off fuel. In the tank is two year old premium unleaded.
2. At warm idle noticed occasional mild surging
3. Noticed that at high load, say 3500+ RPM, audible pinging.
4. On the way home filled up with 87 unleaded, took about 10 gallons
5. After the fillup, pinging was much worse
6. Checked timing, base at 10* on balancer, hmmm.
7. Since pinging was so bad, dropped it to 5* indicated
8. Test drive, pinging substantially reduced but still occasional ping at higher RPM WOT.
9. Warm idle is now about 150 RPM less (down to around 750 on the tach) and surge is almost totally gone ... but not entirely.

Huh? W...T...F...? It's sure acting like 10* ain't 10*. I mean ... 5* and still pinging? Good grief. If it were an OEM balancer I'd say it was spun, but this is my expensive Romac balancer. I find it difficult to believe it could have spun, especially with relatively few miles (about 10K).

Anybody have thoughts on this? I'm stumped. Perhaps it's been so long since I've worked on a 5.0 that I've lost my touch. LOL.

1TallMF said:

Try cleaning the MAF. Thats often the culprit of a pinging problem...

Click to expand...

Tried that already, it was my first target when it was surging .

I wouldn't be surprised to see it's a fuel issue, and contrary to what I would have guessed, it might be a lean idle condition -- pulling the vacuum from the FPR steadies the idle. Hmmmmmm.

HISSIN50 -- essentially that's my plan: drive it repeatedly and see if it starts to resolve itself. I don't think it's in serious danger of damaging anything, and over time it does seem to be improving somewhat.

If it doesn't clear up in the next few days, I'll probably spring for new O2 sensors next, since the ones I have now have unknown mileage on them.