Absense of flywheel shims?

[slipnfall]

Hi there, The car in question is a '92 S13, about 130k on chassis/MT, rebuilt DE(20K, runs great), Exedy OEM-replacement clutch kit, new slave cyl, Redline MT90 m/t fluid, open diff.

Now, the problem I'm having is really annoying: at very slow speeds, warmed up or not, the car bucks pretty hard when I change throttle position. For instance in bumper-bumper commuter/accident traffic: if I don't stay *constant* on the gas in 1st gear, the car will buck forward or backwards(depend. if I let off, or get on the gas). It's not violent or anything, but I'm sure it's noticable by other motorists. Also it seems like there is a slight oscillating bucking, like it bucks forward and backwards ever so slightly when at a constant speed in 1st. It isn't noticable all the time though. Because my diff is whining(it was run low on fluid for a few miles), I can hear the bucking corresponds to the whine(make sense?)

The question I have is, would the lack of flywheel shims have anything to do with this? I had the original flywheel resurfaced w/the new clutch. I am unsure on the amount taken off, but by the looks of it afterwards, the machine shop did a good job on it. It was stepped three-ways, and cost me $42. I did *not* however, install any shims to compensate for this(I didn't know, at the time, that you were supposed to). Could this be part of my problem, or is it due to the cheap clutch kit? New release bearing, disk, pressure place, but I skipped the pilot bearing(don't ask).

I have had three test drives, two at MAACO, one at an independant shop. At the last MAACO visit, I brought this up, and he mentioned the shims.

Any insite? Sorry for the winded post.

-Jamie

[NISTECH]

I have had many flywheels machined in my time and I have never added any "shims" to compensate. there is nothing to compensate for except where the input shaft sits in the clutch disc. There is enough spline length on the input shaft to allow for machining of the flywheel. So honestly I think the guy was giving you a load of crap. It sounds to me like maybe egr is opening to soon. posibly a bad BPT, also check your TPS adjustment could be your at the right throttle for switch open and closing [the switch is opening to late].

[slipnfall]

When you say switch, you mean the BPT 'switch', correct? I checked my BPT a few months back, and with vaccuum on the diafram, it did restrict the airflow. The thing is, I don't know if it was at the correct HG: do you know aprox what ammount of backpressure should be present to open/close the BPT?

I also adjusted my TPS, however now that I have a consult interface, I'll check it with that(voltage in the 'bay may be different than what gets registered by the ECU).

I need to clean up some of my idle valves anyways: at startup sometimes, the rpm's bobble around 1-200, then it catches itself and begins normal warmup.

Thx BTW.

[NISTECH]

No I was reffering to the hard idle switch in the TPS.

[slipnfall]

There is no hard idle swith in the 5spd TPS.

I checked the TPS voltage, and it was 0.4V. FSM calls for 0.5V, so I corrected that. I took a quick drive and noticed my shifts are a bit smoother now.

I also warmed it up, and did an idle adjust. This is really odd: if I disconnect the TPS, restart, idle is right around where it should be. BTW this is how I have been adjusting it up to this point. My idle-air adjust screw is *all the way in*, meaning rpm will not go lower.

Now if I keep the TSP connected, and do the base idle adjust from the consult interface, my idle dropped almost 300rpm! It was barely able to maintain idle, at around 430rpm or so. I adjust it to 750(screwd the adjuster out), and restarted. RPM's idled at around 1.5k. I blipped the throttle a few times, held it, then restarted again. Now the idle is back around 750, where it was before.

I then reset the self-learn: I just moved from PA to NM, with quite a change in elevation. Hopefully over the next week or so things will improve.

Thanks, I'll keep this thread updated.-Jamie

[s13sr20chris]

by your vast knoledge i assume this is not a misfire?

[slipnfall]

You know, there is an ever-so-slight misfire at idle, every 1.5-2sec's. Or what I think is a misfire. It's not noticable unless you are in a closed space(garage), where you can here a faint drop in exhaust(stock) note: very subtle.

NGK plugs, and the wires were ohm'ed out. However the cap/rotor is a cheap auto-store brand(was eager to get it running after the rebuild).

I don't think it is contributing much to my problem though.

NISTECH: drivability seems to have greatly improved, we'll see once I hit commuter traffic next week. Idle rpm has stabalized.

[s13sr20chris]

ok, just wondered because if you had the pulsating, load related, skip of an ign miss that would be different. you just have to feel it.