Captain Obvious

And for today's amusement, the part of Captain Obvious will be played by siteunseen.

Oh yeah. Got it. Duh.

What do you mean by that? Do you mean the same amount of fuel spritzing from each injector? If so, that's the way it's supposed to be. Why would that bug you?

I wanted the above to stand alone, but as to your other questions about the switch... You can get the key-in switch out of the rest of the assy without dismounting everything. The only tricky part is prying off the indicator ring that shows the key positions (LOCK - OFF - ACC, etc). If you can pry that off, you can pull the switch out and replace it without having to dig any deeper. Personally though, I'd just bite the bullet and pull the whole thing off the column and do it on the bench. It might be just as easy in the end.

You don't "need" the shear bolts. They are a theft resistant device intended to make it difficult to disable the steering lock by taking the whole lock assy off the steering column. But honestly, I don't think any thief is going to mess around with it at all. One or two well placed hammer whacks on the top of the assy would probably crack the lock assy right off the column regardless of what screws were used to hold it on. Even if all the screws were traditional "normal" hardware, I don't think a thief in a hurry is going to take the time to remove them. Just crack the whole thing right off the column. Whack. Done. Unless there's some non-stock additional theft resistance stuff installed, I bet I could steal most Z cars "gone in 60 seconds". I've not tested the theory, but I'm confident. it would cost me a window (if the doors were locked), a steering column clamshell, and an ignition switch assy. With nothing more than a hammer. Less than 60 seconds. Gone. Let everyone think about that and take the necessary precautions.

If I was desperate, I believe my conscience would allow me to re-use the outboard bearing even after pressing the stub back of once it had been installed. The outboard bore is sized such that it's a press fit, but not a uber tight one. That's why the slide hammer works. If it were a real tight press fit, you'd need hydraulics to take it apart because a slide hammer wouldn't cut it. However, I'm not sure I'd do that if they'd been assembled and disassembled ten times. In any event, it's academic since new ones are on order. I also really really doubt it's a bearing issue. Even without seeing the parts, I'm at 90% sure the issue is the stub axle and not the bearing. Just for the sake of the investigation, I hope you can eventually conclusively determine exactly what was going on. I like the forensic stuff!

Yeah, I definitely think there's something else going on. There's absolutely no reason you should need to disconnect the WTS to improve anything. Disconnecting that should do nothing but produce billowing clouds of eye burning rich fumes. Have you checked the timing with a timing light? Should be able to get a quick and dirty measurement if you can keep it running long enough. Are you sure you have the thermotime and WTS connectors in the correct positions (sorry, but have to ask). If you think you're looking for an intake leak, you could smoke the system. The injectors are powered through the dropping resistors as shown. Bank of four and back of two. On the low side, they are grounded in groups of three. (1, 2, 3) and (4, 5, 6) through the two output power transistors. Wish I was closer to give you a hand.

I like the line down the middle of the garage. Your side. My side. Your side! My side! Stark would be happy.

I think the best way to look for runout would be to put the whole thing together as intended and then indicate (mag mount on the strut tube or something) off the hub. Maybe check both along the drum mounting surface for runout in the longitudinal direction, and also along the four rounded sections of the outer perimeter of the squared off hub for runout in the axial direction. Of course, this is all assuming the old rusted hubs are clean enough to even get reliable measurements. Did you make double dog sure that the distance pieces were square ended? Some of the distance pieces that have crossed my bench had been modified by previous handlers and were ground on one or more of the ends chasing a problem. Not only were they too short, but they weren't square on the ends anymore.

Jason, Oh! Sorry! I must have gotten my wires crossed... I thought you were on the road already. It's easy for me to rule stuff out from the comfort of my chair, but I really doubt that it's an issue with the new bearings. So I think that if you're still chasing this issue, you really need to figure out a way to stick something down inside the hub and take a direct measurement on the distance between the two bearing mounting surfaces and see if that number lines up with the length of the distance pieces. Sacrifice a pair of cheap calipers like I did or something.

I considered something like the lathe, but the problem is that even though you can chuck something up and adjust it to be perfectly centered (within the limits of your measuring equipment), that centering is still only at one point along it's length. The jaws are never good enough that you can assume the shaft sticking out of the chuck is perfectly normal to the chuck jaws. The optical method you described crossed my mind as well, but I don't know if the gap would be large enough to see. I've got a granite block designed for such things, but don't know if I would be able to see a quarter thousandth gap even with a strong light. And a quarter thousandth off from center at the journal could translate to more than that at the edge of the outer bearing race. Back when they made the stub shaft, they turned it "between centers" (That's the two little holes in the ends.) To produce the shaft, they mounted the raw stock between two points that were located in those holes. But the problem now is that those holes are all rusty and worn and I doubt you can trust the accuracy anymore to the level required to check the journals for runout. But if you could, that's probably the right way to do it. Fixture the whole thing up on the granite block... Mount the stub between centers and indicate each journal. I'm not a machinist and I'm sure someone working in a metrology lab would be able to do this in a snap.

Woof. I feel for ya. Do the math. Get the grades. Collect the paycheck. In theory, it'll be worth it in the end.

If the control loop is working properly, then theta should be very small. Problem is to make the control loop work properly. Actually for the second section, if you are allowed to use the feedback pot on the pendulum shaft, "theta" becomes a "concept". You just need volts: "The pendulum angle is measured with a single-turn potentiometer, with ±10V output corresponding to ±160˚ of rotation" That means you've got +10 V when the pendulum is almost horizontal in one direction and -10V when it's almost horizontal in the other. You've got +/-16 degrees per volt or (the inverse of that) 125 mV per degree around vertical. You're striving to keep the pendulum pot output at 0.00000 volts. And every 125 millivolts you are away from that is one degree off vertical and the sign of the voltage will tell you which way you are off.

Cool. It's money, but those bearings aren't the kind of thing you want to do any more times than necessary. Glad to help and good luck with the rest of it. Keep us posted as to how it all turns out. I'm having a hard time picturing a good way to measure things to look for problems (like a bend) with a stub axle. You need good reference points and I'm not sure what you would use and how you would fixture it. The only precision surfaces on the axle are the bearing journals, but how would you detect a minute bend in the shaft between the two? What you're really looking for is that the two bearing journal circles are not on the same axis center anymore. How would you fixture to detect that?

Wow... That's no fun. At all. Due in two days, huh? I'm assuming this is a final project for a control theory class? I can't give you any hard answers, but might be able to help a little bit in some areas. First thing to do would be to define the project... It appears to me that there are two major approaches that should be applied to solve the problem: a) First approach (the "classical control method") in which the single output of the system should be the cart position (NOT the pendulum angular position). So the only thing you have is the force required to move the cart. If the pendulum is not vertical, the force required to move the cart in the direction of the (off center) pendulum will be greater than if the pendulum were perfectly vertical (in equilibrium). And the force required to move the cart AWAY from the (off center) pendulum will be LESS than equilibrium. So it sounds to me that the "classical control method" would be to rock the position of the cart back and forth (sinusoidal) and measure the force required to move it. That force should be able to be derived by the current necessary to rotate the motor. That's where the PD lead-compensator stuff comes in... You should be able to keep the sine wave constant and as small as possible. And there is some doubt about the success of this approach as laid out in the original problem. You are supposed to program it all up this way and see if you can make it work. And if not, explain why not. For example, the control loop may not be stable and you may find that the sine wave required is increasing in amplitude until you run out of track length. I suspect this approach is not very robust and resistant to outside applied interference (the bump nudge described in the problem). b) The second approach allows the student to utilize the position feedback on the pendulum and it becomes a more direct control loop. Move the cart in the direction the feedback pot tells you to and strive to keep the output of the feedback pot at 0V. That should be much faster and more accurate feedback than using the cart force and should be able to do a much better job of compensating for externally applied interference. (Proof is left to the student.) If I understood the project correctly, then I would break it down into pieces: Write some equations for the force required to move the cart independent of the pendulum. Write some equations for the force on the cart due to the position of the pendulum (this is the part that Blue started working on above). Then combine the two. Write some equations for the relationship between the rotation of the shaft and the linear position on the cart. Write some equations for the electrical energy required to rotate the shaft. Etc... I'm so glad I graduated!!

Well that's pretty definitive about the stub shaft. Hopefully the replacements from ebay will solve the problem! That would be a really easy solution. A lot easier than pulling everything back apart and starting completely over. Unless you have a neat way of pulling the outboard bearing off the stub shaft without putting pressure on the balls, you might consider using yet another new outboard bearing on the new replacement ebay stub. Depends on how you feel about reusing the one you already pressed on. And all this talk about wheel bearings and the resurrection of this thread reminds me... We never heard back from @Jason240z about the final outcome with his car. I believe his car is back on the road (so his issues have been resolved), but I don't think the loop was ever closed about what the problem was. Hopefully he can fill us in?

Yes, the vacuum source is ported. There should be no vacuum at idle, and then slightly above idle (think light cruise), the vacuum peaks. From there, the vacuum will drop off above that point down to zero at WOT. So it never "retards"... It just provides no vacuum at idle, so the timing just reverts back to the base setting And about the temp sensor... Unless you are in Antarctica, I don't think there should ever be a situation where your engine would be cold enough that it would need the sensor to be completely disconnected to run right. Even with constant cool water from a hose, that temp sensor will be getting way warm enough to be providing meaningful input to the ECU. If you need to disconnect it to get the engine to run, then I think there's a problem somewhere in the system.

Yeah, that's not cool. If that shaft is straight, there's no way you should be seeing that. Maybe out at the edge of a big rotor or something, but no way you should be seeing that at the axle without the mechanical amplification of big disk. Are you seeing that on both axles? One of them turned out OK, right?

I understand the ASCII art perfectly. And if the seating surfaces are not square to eachother, there will be big problems. There will unquestionably be dimensional changes caused by the welding operations and my expectation would be that T3 would have started with raw materials and designed the housings such that after welding, there would be extra material that would have to be machined off to square up the surfaces and make them precise. Above, you mentioned looking for a thousandth or two, but when it comes to bearing placement, you're actually looking for the tenths of thousandths. A thousandth or two is usually way way way too much. In fact, a thousandth or two would make the difference between 200T required to press a bearing in vs. one that drops in free with just it's own weight. If those bearing bores are out of round and/or not coplanar to within a fraction of a thousandth, then I think you ought to put in a call to T3.

So when the temp sensor input is actually making it to the ECU, how does it run? How do the plugs look? I'm a little concerned about the pic you posted of the insides of the AFM. Since you have a good report with the PO's mechanic, can you (did you) ask him if he adjusted the AFM to try to lean things out?

I'll do the same and stop poking at it. Thanks Mike.

Excellent!! So maybe all of the fuel pressure stuff was a red herring caused by questionable test equipment and procedures? In any event it reinforces the belief that it just looks like most other old 280Z's that are running either really rich or really lean because of a whole bunch of interrelated issues like dirty connectors, improperly placed connectors, and vacuum leaks. So you found the first, highest priority of those, but there are probably others of lower contribution and impact. The remaining issues are probably what the previous owner's mechanic was chasing to get it to pass smog.

Haha!! No, they do not! So... Now it's been three days since this post was started, and the OP hasn't ever signed back into the forum since. Brand new user, all hot to trot about purchasing a car (or two!!) and hasn't been back to discuss all the input from the fine members here. Maybe he's totally consumed with a huge Easter party prep and just too busy to come back, but I just get a bad vibe from the whole thing. @Mike, I'm thinking maybe give it another day and then delete the whole thread (and user) if nothing changes? Been a while, but wasn't there a rash of spam bot users that signed up a while ago? Year ago maybe? And all of their user names were the same format... Name followed by a couple numbers IIRC?

Glad to help. Before you rip everything completely apart and start over from scratch, I like your idea about moving the stub axle from the other side (that spins ok) and seeing what happens when you install that stub axle in the problematic housing. I agree that could be a good clue if the problem follows the housing, or the stub axle. In any event, I hope you get to the bottom of it.

Been another half day and still nothing from the OP. Wonder how many additional hits have his links seen since he posted this?