So if anyone remembers me, I had a car that was jerking and running a bit unsteadily (75 280z), and was able to rectify this by cleaning a bunch of the electrical contacts.

I've since done some more homework and determined that the primary culprit was the TPS; my TPS seems to get dirty very easily (and usually fouls a day or do after a rainstorm if I don't clean it immediately after). This will either cause an unsteady idle, or uneven performance at more than 3/4 throttle, so it's easy to diagnose. I have the cover securely on the TPS, so I don't know how it gets fouled, but as long as I spray it with contact cleaner every couple months, the car runs fine as my daily driver.

Also, if the idle contact isn't just BARELY touching at idle, then the jerking behavior returns. If the idle contact on the TPS isn't set to where it disengages if you crack the throttle even just a bit, the car runs awfully.

...Is this normal? I don't care too much, seeing as I can keep it clean and adjusted and have no problems. It's sort of odd that my Z31 with L-jet doesn't need that sort of attention to the TPS, but whatever.

The one thing that does sort of have me wondering, is the last bit of bizarre behavior the car exhibits. Until it's 100% warmed up, after the iac has closed but before it's all the way to operating temp., idle will dip down to 500 momentarily on releasing throttle, then climb back up to 900 where it's set, after about a second. I wonder if the car is looking for the leaner TPS setting to kick in a bit sooner on release of throttle, but again, if I don't have it just barely engaged at idle the car bucks. Once the car is totally warmed up though, after 15-20 mins, everything works normally.

These are my observations: feel free to comment upon them as you like

Edited February 16, 201213 yr by NiiChan GT-R

Maybe adjust dash pot and/or bcdd to try and fix the off throttle bog before warm up.

I adjusted the dashpot a few months ago, where previously it had no effect on throttle travel, I screwed it in to provide for some damping... I could feel the difference when shifting, but the cold bogging remained, so I shrugged it off for the time being.

The BCCD I haven't paid any attention to... I remember that it (I assume) made revs hang at about 1500 after releasing throttle at one point a long time ago, but I haven't noticed any effect from it in a while, so I'll take a look at it...