Captain Obvious

And by the way, the other thing you do with the Steinhart-Hart coefficients is use them to build your look-up table. There aren't nearly enough data points in the FSM and if you try to linearly interpolate between only what's published, your error will be huge at the midpoint between your table points. Back in the Mesozoic Era when I used to do this... First thing you need to do is determine the amount of acceptable error. Then you calculate enough data points along the curve such that the linear interpolation between your table points never varies more than your max error budget from ideal. Works out such that the table points will be farther apart in areas where the curve is naturally more linear, but in the areas where the curve is nasty, you'll need more points. Did I say that right?

Haha! Honestly, I'm not sure which I'd rather tune... Off the top of my head though, I'm going with the triples.

Lenny, are you kidding me??? All that floating point and you're gonna use a look-up table for the conversion? You don't have to be embarrassed... I'm embarrassed for you. I'm just kidding of course. But if it were me, I wouldn't even ever convert the resistance to a temperature. The ECU doesn't really even ever need to know the "real" temperature in degree units. The only reason you need that is so you can display it on your interface. All the ECU really needs to know is how much fuel to add to base at that resistance (voltage actually) sensor input. Lookup table... Volts in, and increment to base pulse width out. Who cares what that is in "degrees". And BTW, there was some problem with the numbers in the FSM. I did a post about it a while ago. Let me see if I can dig that up. On edit - Found it: http://www.classiczcars.com/forums/fuel-injection-s30/48782-water-temp-sensor-air-temp-sensor-resistance-charts-typos-manuals.html

My read is that everything is working as best it can and you're simply at the mercy of mid-seventies control technology. Once the engine is fully warm, it will idle smooth at 800-900 with no AAR help, but it sounds like the AAR is closing off before the engine has warmed up to the point where it will sustain that idle. Unless you turn up a hard issue with one of the FI components, your (only?) choice would be to adjust the AAR so that it's open more and takes longer to close. Of course, that will mean that your initial cold idle will be higher, and you might not like that, but that's what I meant about being at the mercy of the old tech. The AAR's closing speed is based on things that are out of the control of the ECU, and there's no ECU control of the idle speed. It's the best they had back then.

And the potential confusion about the proper install direction of the rubber bushings continues... If you look closely at these pics, you'll notice that they couldn't make up their mind and installed one bushing each way. One had the thick rubber section towards the frame hole and the other has the thick rubber section towards the large washer: [ATTACH=CONFIG]66175[/ATTACH][ATTACH=CONFIG]66177[/ATTACH]

Lenny, A while ago I derived the Steinhart-Hart coefficients for the air and water temperature sensors. Don't know if you're beyond this point already or you were even planning to use this method to determine temperatures, but here's what I got: C = 1.89571E-07 B = 0.000257545 A = 0.001305386 These numbers are based on info from the FSM and I believe they are slightly suspect. If you find from experiment that they are off a little, let me know and I've got a different set of cooefs that were derived from info directly from Bosch instead of from Datsun.

Chas, That setup was put together from two kits and I did it that way based on info gleaned from other's previous experience about breaking T/C rods. My PO had put poly at all four bushing locations (so I already had the poly). I replaced the rear poly bushings with rubber ones from that AC Delco kit in the pic. I bought two of those kits because I needed washers and sleeves for both sides, but only used half the bushings. I highly recommend that AC Delco kit by the way. Quality was excellent. I just wish I had taken a new pic after I spun those rubber bushings around. I hate posting that old pic knowing that it risks others making that same mistake simply out of example. It's on the car now and I didn't take a pic after I fixed them...

Everything should come off the rod. In this pic, there are still a few old bits rusted into place on the donor rod. That large washer has to come off, but it's being held into place by a rusted into place sleeve tube. There is also a smaller washer behind the large one that you can't see in the pic. [ATTACH=CONFIG]66118[/ATTACH] Here's a pic of a bushing kit. Two small washers, two big washers, two bushings, a sleeve, and a nut: In application, from front to rear of the car, it goes: Small washer Large washer Bushing (with sleeve in center) Frame of car Bushing (with sleeve in center) Large washer Small washer Nut Here's a pic showing the install order. This is what it looks like with urethane in front and rubber in the back. Note that the concave portion of the large washers should be away from the bushings. Also note that the direction of the black rubber bushing is wrong. The thicker portion of the rubber bushing should be towards the large washers, not towards the frame. I originally installed them incorrectly and later took them back off to switch the rear bushings around.

Right. My bad. I have little experience with the early years and it's certainly conceivable that they changed the hardware over the years. By the time they got to the 260, I believe they were using the self-locking single nut, but I have no significant experience with anything earlier than that. Even if they did use two nuts for the lock feature on the early cars, I bet they superseded it with the self-locking newer style. There's a "concourse" detail for you to keep an eye out for at shows. :bandit:

I believe the stock arrangement is to use a single self retaining vibration-resistant nut on the bushing end of the rod. One of those all metal styles that have a few purposely distorted threads at one end. There's nothing wrong with using two normal (not vibration-resistant) nuts there instead, but in theory, if you're using the correct stock nut all by itself, you should not have to. Just remember that the stock style nuts never hold as well the second (or third, or fourth) time you try to re-use, so if there's any question as to their ability to hold themselves, you should just buy new.

I'm seeing more issues than just a bad bushing... There is supposed to be a threaded portion on the end of that rod, and it's not there, The whole rod snapped clean through. You're gonna need a whole new T/C rod for that side. Look closely at the other side for more details.

I just noticed that I had the constituent percentages swapped above... The correct mix is 75% argon / 25% CO2. Sorry for the simple stupid mistake. I would edit it up above, but it's too late. I can't change it. Maybe the mods will fix it for me?

Me neither. I'm no welder! I know just enough to be dangerous. Wait a minute... I think I can say that about lots of things!! :laugh:

Yeah, I didn't know it either. I thought that the only reason people used the CO2/argon mix for the MIG was because it's cheaper than straight argon. In my defense, I'm claiming "bad advice from counsel". I bounced the idea of sharing the same tank between the TIG and MIG off a few people who should have known better, and I was told (incorrectly) that the only difference was cost. Here's to hoping that I can pull you out of that fallacy faster than I was pulled out. Here's the doc that pulled me out. Lots of stuff in there, and way more in depth than anyone except a professional welder in an industrial setting would need to know, but in the early sections, there's info that applies to us "hacks": http://www.lincolnelectric.com/assets/global/products/consumable_miggmawwires-superarc-superarcl-56/c4200.pdf Here's hoping I can pull out of the wrong shielding gas fallacy sooner than I was pulled by someone else.

Glad that you were able to narrow the problem. That makes things much easier. Thinking out loud, the only "external" thing I got that would put extra heat into the ignition module would be the lack of a ballast resistor where one is required. Maybe the PO didn't get it hooked up right and/or shorted it out somehow? Without the ballast resistor, you run the risk of pulling too much current through the ignition coil, and that might be enough to mess with the ignition module. I've not seen it, but I guess it's possible. Just to be prudent, you should check your coil and ballast connections carefully and make sure everything is done correctly.

Yeah, but it's just the principal of the thing.

Tis a puzzlement to me as well, but I can tell you... You aren't the only owner with this issue. I, on the other hand, ran SU's for quite some time and never had this problem. I don't ever remember having to add fluid. Unless I took it out on purpose, it never changed. And I doubt the gas smell has anything to do with it. You pull a part out of your carb and it smells like gasoline? Color me surprised!!

Good pics. I don't see anything that screams obvious problem. Two things catch my eye. First is a couple missing clamps on things like the brake booster and PCV vacuum lines. Not the cause of your problem, but might be providing a little vacuum leak. Second thing is what's with the hole in the middle of the EGR mounting casting. It's not sucking air through that little hole in the center, is it? As for potential heat related ignition issues, before you drop time or $$ on a different system, you could shoot a hot hair dryer at your existing module to try to recreate the problem. And buy a $5 can of circuit cooler at Radio shack to cool it off and see if the problem goes away.

You're using the wrong shielding gas. For general purpose MIG on carbon steel, you should run 75% CO2 / 25% argon mix. If you use 100% argon with the MIG, you get proud beads and very narrow fingerlike penetration. You'll be tempted to turn the power up to get the bead to spread, but that's not the solution. The solution is to use the correct shielding gas. I went through this myself about a year ago because I was trying to minimize the number of bottles I had to maintain. I figured that I could share the same 100% argon bottle between the MIG and the TIG, and I was mistaken. It doesn't work right.

Since the time of that other thread, I have disassembled a round top suction piston and have verified that the round tops are machined from one piece of steel and don't have any seams at the bottom. So if you're running flat tops, they might leak out the bottom, but your round tops can't. I'll snap some pics of the round top tube in disassembled state when I get the chance. I know that won't help your diagnosis though... Only makes it more difficult.

So the car started it's life as a 260 with a manual trans, right? Who swapped out the original flat tops for the current round tops? Did you do that swap, or was it like that when you got it? Also, how much of the original 260 stuff remains now that you're running round tops? Did they swap to 240 intake manifolds and balance tubes too, or are you running the original 260 stuff there? I'm just trying to get my bearings... Got any engine bay pics?

There are no seals involved. Everything is metal on metal. Nothing that would dry out. Here's a recent thread that dealt with the same question: http://www.classiczcars.com/forums/carburetors-s30/46939-su-oil-consumption.html

Yes, that sleeve is in there to act as a stop for the large washers, and yes... Even with that sleeve installed, the bushings deform significantly when the nut is tightened to bottoming. I'm with ya, it's more deformation than what is usually considered "normal", but it's correct. That's why the bushings you took out look very little like the new ones you're putting in.

Haha!!!! Good call! Thanks for the laugh!

Same thing has been said about me at times.