When Colin visited me this summer, we accomplished a lot, but one of the things we didn't have time to sort out while doing some AFM tuning was what he termed a "nervous idle." It will run fine through the RPM range with the exception of anything below about 1500 RPMs.
Well, since then, I've been periodically trying to address this crummy idle as well as the re-emergence of my bucking issue. I suspect they are related.
To address the bucking issue, I tried narrowing things down and have done the following (in no particular order):
- Adjusted my valves (several times...best seemed to be to adjust them warm at contact plus 1/2 turn)
I rebuilt my distributor
I removed my electronic ignition and installed points
I gapped my plugs
I actually went and purchased and installed one-by-one, a new coil, cap, rotor, and wires (needed a set of spares anyway)
My tired old battery crapped out so I purchased a new one along the way
Replace my fuel filter (and bought a spare)
Timed my engine to 30* BTDC (hoses off)
Searched and searched for vacuum leaks, but didn't find any
- <1500 rpm: LM-2 puts out nonsensical high AFRs, engine won't idle, fuel pressures 38-40 psi.
1500 rpm: lowest level that engine is smooth, AFR=14.8, fuel pressure=32 psi
2000 rpm: AFR = 14.7, fuel pressure = 30 psi
2200=2400 rmp: anytime I go through this range, there is a higher pitch vibration sound.
2500 rpm: AFR=14.7, fuel pressure = 30 psi
3000 rpm: AFR = 14.5, fuel pressure = 30 psi
3500 rpm: AFR = 15.0, fuel pressure = 30 psi
The last possibility I can think of that might be wrong with the system is that my FI harness is in a deplorable, but seemingly functional state, the RPM input wire being the worst condition. I want to get a new one, but $400 and 5 weeks starting Jan 12 is quite a ways off and out of my expense availability at the moment. I can get a used one from Avery's for $175, but that's used (and substantially more than the ones I've seen on the Samba classifieds) which comes with it's own question marks and no guarantee it'll work. What's more, my bus is a late 76 model so it has 7 pin AFM connection, mechanical EGR, and a full throttle microswitch.
Running out of ideas here. Any suggestions?