I believe it has a misfire, which I initially thought it was some sort of lash in the driveline. At low throttle input, just maintaining speed it will jerk constantly but sort of randomly, feels jittery. It's fairly subtle but it's there. Most noticeable under 45 mph or so in 2nd and 3rd gear, just under the ok I'm accelerating threshold. When you give it more gas it seems to turn into a very fast jitter, fairly even almost like a vibration. Over half throttle to full throttle you can't really notice anything wrong. It does seem to have gotten better while I have been chasing it as well as my idle and cold running, but man have I gone through just about everything. What I've done:
- Replaced or checked every vacuum line, no leaks.
- Valve adjust to .009 cam side. Note this thing has a lot of miles but the cam looks great.
- Regapped spark plugs to spec.
- New dizzy and rotor.
- Wires are only a couple of years old.
- Tested ICV, why not.
- Swapped in known good AFM.
- New fuel filter.
- Swapped in known good FPR.
- Tried a known good coil.
- New CTS.
- New O2 sensor, old one tested fine but replaced anyway.
- Tested TPS and adjusted anyway.
- Checked main and valve cover ground.
- Unrelated but replaced crank/flywheel position sensors, the 37 year old connectors were crumbling.
I think I've covered pretty much everything I've been able to find in Tech Talk about similar issues. If anyone has any insight or tips I'd appreciate, sort of banging my head against this one. Cheers!
Bonus, we moved back to Portland from NYC in January, drove this thing the whole way after it had pretty much sat for two years. What an enjoyable experience! Car was flawless, just ate it up cruising at 80-85 all dang day for 4 days straight. Probably why it needed a new everything once we got back to Portland. Now has completely new braking system and a new starter, CV shafts, blah blah blah. Other than the misfire and a shifter rebuild, it's so dialed and drives so well.
