Dave WM

I missed the idle screw has no effect. That is indeed a clue. Have you tried smoking it for vacuum leaks? Blocking the front of the AFM with a foam cup, then blowing smoke from a cigar into the intake manifold (at the brake booster port is a good place), look for smoke. Besides poor electrical connections to various sensors (and grounds), vacuum leaks can plague EFI, it has no O2 sensor and can not compensate for problems if there is anything that is out of spec.

the FSM is your friend. You need to start by checking resistance readings at the 35 pin connector. Don't anything more until you do that, or you could just be adding layers of errors. Main one to focus on is the temp sensor (not the gauge but the sensor that goes to the 35 pin connector and is crucial for the ECU to set the air fuel mixture). Also when ever I hear the word "deletes" it make me cringe. Deleting means the system no longer is setup to the FSM, "could" impact how the test work and the results. Reminds me of the word "upgrade" that one gets thrown around a lot, and I would say maybe "changed" would be better. sounds like it did work at one time (but for the idle, which sounds like the aux air control, covered in the FSM). So each change you make now gets you further from a once working system. Hence the need for checking before any more changes.

I used the MSA comp gasket, no sealant. Two things, don't over torque it, and if there is a leak, it maybe the side seals, they look a lot like a pan leak in the rear of the pan. If you keep having leaks, consider replacing them. You can check them easy if you are doing a clutch (rear main and side seal leaks are easy to see with the flywheel off). But if you don't want to pull the flywheel just to check you can do the side seals with just the pan off. Its a bit of a PITA but not that bad. Replacing them solved my "pan" leak.

I would have been happy to pay that for a new tank for my 75 280z. How different are they? I know in 77 they went with the space saver tire and completely changed up the tank, but this new tank looks a lot like my 75.

I have heard that a lot about PU bushings, why I bring it up when folks start talking about upgrades to suspension. Really depends on what you what, for me since my plans are 0% performance driving, and mostly long distance trips, I wanted to keep it a quiet as possible. I replaced the OE cat back with the cheapo standard size one sold for something like 80$ delivered. it was a tad long, but other than that an easy bolt on operation and keeps the exhaust noise to a very low level. New window rubber keeps the wind noise out. Its no lexus but its not that far off from one either.

As for the trip, I recall driving one of these (a 1974 260z) when it was new, and my 75 seems to have aged well, It has low road noise, and suspension was soaking up the minor bumps in the road well. The biggest improvement was the new tires, while my old ones looked fine, they caused a wheel shake, I assume it was the tires could have been the rims as I replaced both tire and alum slotted rims with the new tires and steel rims.

I still have the spare engine with the MN42 head. I may after retirement try that one just to see how it goes (just curious and with retirement time is in abundance). As is the engine pulls nicely, so agree, no hurry to mess it up. My goal has been to see how well I could set up for MPG since I like to take long road trips and prefer to cruise rather than blast off.

3.54 stock rear end that was in it with the 4 speed. 80mph at 4k rpm in 4th. with the OD 5th gear Its a bit tall as so I cant really use it until get to at least 65mph (5th gear), would be a problem if I had hills to deal with, as that would make the engine lug even at that speed, but in Florida its flat everywhere. I have a 3.7 spare diff I could install (would prob be a nice upgrade) to make that OD gear more useful around town or on trips to other places with actual terrain to overcome.

ah forgot to mention that, I did replace the intake valve guide seals. I passed on the exhaust guide seals, as I read that they do not account for oil burning. the old seals were "slightly" stiffer than the Nissan OE replacements, the new ones also seemed "slightly" tighter fitting. I get no noticeable smoke on startup. Forgot to mention this is with at least 105k miles, as I owned the car starting with about 85k. Maybe its 205k... If so it has very good compression (about 160-165 psi warm across all cylinders).

Just wanted to document a recent 800 mile trip (central fl to central al) driving at night, mostly AC off about 27mpg, speeds were 55-75 with mostly 65-75. none alcohol gas. a little less than a Quart of oil (28 oz approx. over 1400 miles on the trip odometer set at the last oil change) so about 1500 miles per quart. Temps pretty much right at the E of the temp gauge, guessing this is 175f since that is what I use in the T stat, and it would get there and hold. It will get hotter (so T stat is no longer controlling the max temp) if I drive in the heat of the day with the AC on, then it will get just a little over the middle of the range. this is 95-98f with high humidity and AC on. I think I am going to try the Alum rad I have on the test stand to see if it is able to maintain the max heat of 175f. This also is with the use of a ZX 5th gear overdrive use much of the time (anytime I am over 65 mph). with that setup I get 80mph at 3k rpm. I have the skinny tires at 30psi. They are 185/75 R14 Hankook brand. I noticed after putting this on vs the wider recommended size 195R70 that the car rolls easier. I don't know the effect on MPG with the AC on constant. Overall very happy with the stats, but would like the oil consumption to be closer to 3000 miles per quart (my standard distance between changes). I have good overall compression, can see no signs of oil burning (blue smoke) have no external leaks, so I assume its just the oil control rings letting a bit too much past. the plugs do not present any obvious excess oil, and the book say excess is something like more than 1Q per 600 miles (that seems like a lot) so I suppose from that point of view my oil consumption is not excessive. The oil consumption was based on about 800 miles of the trip and 600 miles of non trip around town (the total of 1400 miles since the oil change). I don't know if highway use vs around town use impacts the oil consumption. lastly oil pressure about 2/3 indicated on a 90 psi max scale after warm up at anything much over 2500 rpm (I would say 90% of the time I am around 2500 on long trips). On a cold engine its more like 3/4 indicated. This is cold as in mid 70's as the cold temp on VR1 20/50 racing oil (high zinc).

thought I did that but will double check.

if I make slow near full lock left turn (coming out of a parking lot example) I get a pop sound that comes from the front of the car right hand side I think, and can feel a release in the steering wheel at the same moment. It seems to happen at the exact same spot on the steering wheel position. it happens every time, but you need to "reset" by turning back straight (you cant just hover over the spot and get the same effect by moving a few degrees back and forth. I tried turning the steering lock to lock with it not moving, no problem. I can turn the wheel fully while stopped and the pop will happen as soon as I start to roll with the wheel fully cranked to the left. I have new ball joints. the left tie rod seems to have just the slightest amount of play in it. I can grab the inner and push pull and detect "some" movement whereas the driver side has zero. the outers have no play at the wheel hub. does a very slight amount of play in a inner tie rod sound like the kind of problem that presents with the problem pop sound I have described?

now I have to check the valve cover.

I got one, thought it was part of the cap, pretty hard, but it def is a separate piece. the drawing make it look wider than it is.

needs correct wheels. Nice looking car.