Dave WM

Parallel flow condensers are supposed to be more "efficient" than the serpentine stock unit. I have read that the down side to PF is if you get junk in them they can not be flushed as a serpentine style (a single tube that snakes back and forth with fins on it). the size is just a matter of getting it all to fit in the allotted space, Not sure if oversize it would help a lot since you have to have air flow thru it, and the OE size pretty much matches the opening in the rad support. Now as to why would you need a PF flow, I would think IF you are going R-134a a condenser type is generally PF, I presume to better match the needs for R-134a, hence my recommendation. I am not an expert in AC either, just what I have picked up reading and working on my own R-12 unit. I was lucky to find a NOS condenser so that is what I used. Before I got that I bought a reconditioned one from zcardepot IIRC. I was not very happy with that one, so I am glad I found the NOS. IF I had to do again and could not find a NOS I would look into a PF. However if you wanted a serpentine OE drop in style I think I have seen brand new units made. Not cheap like the evaps they are expensive but they are out there. Again I would prob go PF though IF I wanted to go R134a. You can tell a lot with manifold gauges, if the pressures get too out of whack (like the high side going too high with R134a) then there is the option of adding a electric fan in front of the condenser, operated on a trinary switch (low cut off high cutt off and fan on). Typically the pressures soar in high temps with little air flow over condenser (idling in traffic). In that case a fan may come into play. With R-12 the stock setup works as is.

I think the plan will be as follows drain oil, keep a sample of the 2500 mile VR1 run the rotella for 1000 miles, drain keep a sample compare how dirty it looks to the 2500 mile VR1 Refill with VR1.

the carbon canister is part of the emissions control system. It collects fuel vapors from the fuel tank, stores them in carbon, then when the engine is on, a ported vacuum signal opens the canister to vacuum into the intake manifold, thus burning the vapors that would have otherwise been dumped into the outside air. There is a filter element on the bottom of the canister that draws outside air into the carbon while sucking the fuel vapors. this outside air cleanses the carbon so it will be ready to accept excess fuel vapors that occur while the engine is off and the gasoline in the tank vaporizes. You can check to make sure you have ported vacuum by feeling small vacuum hose and operating the throttle while the engine is running. the large line under the vacuum servo goes to the intake manifold, the other nipple on the canister goes to a rubber line that connects to a hard line that runs along side the fuel and brake lines to the rear of the car. For the system to function as designed you should make sure the line back to the vapor canister in the rear quarter is not "stuffy" (plugged up). there will be some resistance to air flow as the rubber line that goes to the carbon canister has a restrictor and the there is a two way restrictor in the line near the rear of the car as well.

just get some help removing the dash for the install. being old it will likely crack unless you are very careful not to torque it. Texas you HAVE to have good A/C same here if cen FL would not be able to drive it 8 months out of the year without it.

disable 6 when cold does it have any effect on idle? after warm up disable 6 does it have any effect on idle? swap 6 with 5 repeat test cold and warm the video did not work for me btw. Lastly something to consider even when everything is working, the enrichment circuit adds fuel right after startup for a few minutes, this is above the normal CSV and temp sender enrichment. Its very hard to remote diagnose even if the video worked. You mentioned a strong gas odor, that would make you think its maybe not getting a good spark and perhaps when it leans out some after warm up #6 is just not igniting. the color tune will help with that. put it in 6 observe the color (should be yellow cold) then watch to see if it goes to blue (correct mix) and then dark but for a spark (flame out). the car may run just a tad rougher when idling after fully warm vs when cold just do to the leaner enrichment. I am not talking big differences here, at least on my car that is the way it is. I have thought of adjusting the AFM bypass to see if I can richen up the circuit (presuming that is why its just a tad rougher idle when fully warmed up), but have never bothered to try it as its really minor. The EFI is rather primitive (batch fire, open loop) so its prob setup to pass emissions on the lean side of things. I don't think the above statement is your issue, just stating my cars operation from cold to fully warm.

going to change my oil soon, 2500 miles on VR1. Plan to use rotella T4 15-40 unless someone yells "DONT DO IT DAVE" my thinking on this is the T4 may have a better detergent package to help clean up carbon deposits that may be in my 100k+ engine. I have been using the VR1 for about 25k miles again avg about 3k between changes.

I know exactly what you mean. I like the way the OE system controls work, I find them easier to deal with that modern stuff to get what you want. Another thing to remember you will need to get the under hood air switches and a idle up servo and the vacuum bottle, hopefully you can score a complete system. You should be prepared to pull the dash even if you go all OE, Its not that hard to do and will give much better access to the workings. If you go after market pulling the dash is a given, but even OE its a good idea. You can service the heater core and valving while its out. IF your dash is cracked you should look into a vintage dashes replacement. A good time to do that as well. The vintage dashes replacement is an excellent reproduction of the OE, not cheap but if you want it done right its the way to go.

you can buy brand new evap with a standard TVX, not cheap (300ish iirc) that is a drop in replacement. I would go with a parallel flow condenser (pick a genereric size that approximates the oe size and rig up some mount hardware) a SD709 and a generic drier, then use the new evap in an OE housing. Using the PF condenser should allow for good use of R134a vs R12. I got my new evap just in case my old one leaks or the tvx ever looses its charge. At that time I would just swap out the evap and stay with R12 since I have a good condenser (was a NOS unit). I prefer the old hitachi SWP types with the sump, they are heavy as a tank but cant argue with longevity (looks OE on mine and runs fine). But the SD709 is prob a better choice if you have the mounting bracket. It prob works better (quiet, light weight), but I always wonder about the quality of stuff like this. I think there maybe some other tweeks if you car did not come with AC as far as making it work, its all covered in the FSM on how to add. Often see the entire AC system for sale on eBay, a good way to get all the pieces then if the evap is bad just replace it with the new one I mentioned above.

doing a trans swap is pretty easy, only hard part will be getting the car up at least 30" off the ground to make it easy. the other issue is getting the exhaust bolts off the header pipe to the exhaust manifold, if they are stuck that is. I priced it out and it was going to cost me like 800$ (clutch/rear main at the same time). I generally don't like anyone else working on my car, just getting it up on the air can be an issue with correct lift points. If you don't have to fight the bolts in the exhaust its about a 7 hr job (swap/clutch/rear main) doing it by yourself. I see Steve J responded while I was posting he is from the area so prob knows folks that do good work if you don't want to mess with it.

no obd this early a car. Really don't understand the high resistance. You are reading from the battery post to the engine block right? also from the battery post to the car frame. You should be able to trace from each connection point to find the resistance. start with the battery post neg to the wire lug that connects to the fire wall right off the lead from the battery. Perhaps you have a poor connection thru a fuse link (IIRC there is a fuse link in series with that wire, I may be wrong about that will check later). Its just a matter of wire tracing with the ohm meter.

don't understand what you are saying. Jumping the cold start vale terminal? the engine is turning over? you mean something your are doing is causing the starter to engage? It maybe possible to energize the starter solenoid by applying power to the positive side of the harness that plugs into the CSV I suppose, IIRC they share a common lug on the ign switch "start". But if that is what you are doing that is the incorrect way to activate the CSV to depressurize, You only want to apply power to the csv, not the harness, and frankly you don't need to do that, just put a rag around the fuel line at the fuel rail and loosen the hose clamp. there is not that much fuel stored, the rag will catch it and keep it from spraying.

just to confirm the above, I checked with my DVM the neg post to the engine block, .1 ohms. So yes if you are getting 31.4 ohms from those locations you have a problem. I would start with the easy stuff, like the cleaning the battery post and cable connection. NO use of dielectric grease please. Just check from the center of the post to the battery cable clamp from there chase the battery clamp to the engine fire wall and starter. You have got to get that down to the sub 1 ohm reading.

drove the brand new 260z to the high school prom. Was on the road yesterday on the radio was disco, yikes... but it did take me back! the new car next to me had some kind of thumping noise, think it was music, but I don't think the car will be around for long, sounded like it was rattling apart at the stop light. My old radio has maybe 5 watts max, that and disco not likely to damage spot welds.

here is a prediction for you, I hear a lot about setting up an electric infrastructure for electric cars, I suspect a much bigger problem will be an infrastructure for the internet.

in the 70's driving was the number one objective for teens, at least males (well other stuff as well but we are talking cars here). I got my learners on my 15th b day, same with reg on my 16th b day. drove motorcycle on my 15th b day, every day of the week. same with car when 16. left in the morning home late at night, if not school, then work (min wage), or social. Home is the last place you wanted to be. So Clearly driving was everything, and we worried about running out of gas back then, why cause then we could not do the one thing that was so central to teen existence. The idea of being driven around would get you laugh at, bullying was the way the social order was maintained. VERY different these days, and I presume every generation has the same experience, therefore trying to project into the future becomes a bit of a folly as far as what will be the driving force with large scale problems. when I was young it was common to see gangs of youths wandering the streets looking for action, now I rarely see young folks or old folks outside, but for a few throw backs like myself out cutting the lawn (that is left to "lawn men" for most folks around me). There was some hope though, I took my dirt bike out Saturday for a ride in the woods, there were a ton of people of all ages out enjoying the outdoors. I drive a classic dirt bike (1978 RM400 Suzuki) and there was a lot of attention by mostly older guys digging on the old bike reliving there youth when they had one.

Or we may find that driving is not even an issue, and oil will pile up. I have not commuted to work in the past 12 years, I suspect with the sudden realization that a LOT of the work force does not need to commute there will be even less driving. With VR substituting for family vacations, with amazon delivering your groceries, with doctors seeing patients remotely, with robots taking over all forms of jobs (hastened by the min wage being deemed a 'living wage", there was a robot doing my 1st job, a porter, at a store the other day) so less people will be needed, next up will be taxi and pilots by machines, eventually we become bags of protoplasm sitting in a matrix. In the early seventies this was all the rage (save the earth, running out of oil, global freezing, opec oil crisis) all the young folks were yelling at the old folks telling them they were messing up the world (remember the crying American Indian in the canoe), so this is nothing new, but I have come to realize (with age) that you cant predict what will be the next real problem. I grew up with constant warnings about dui, well I think distracted driving is a bigger problem, also about kids wasting too much time with TV shows, now its video games. Good luck the figuring out what the next gen issues will be for beleaguered parents to deal with. Good luck deciding where resources taken from tax payers by force should be used. Or just live your life as well as possible without taking from or hurting the other guy. Be conservative with all resources, as you will prob get it wrong trying to guess the future.

took my z out and burned some gas, pumped out some carbon, and loved every minute of it. 75 mile round trip so I could feed some tree rats some pecans, harvested no doubt by some huge combine like machine. Now going to change the engine oil after 2500 miles cause it looks a bit brown.

great movie, "the fountainhead"

can you describe the setup that results in the 45psi on #6? I am not sure I follow what a "live compression test" is. 45psi is for sure a problem. I assume the live test on the others was somewhat higher in psi readings? On compression test its all about being even or at least within 10% of the high number. My standard test is a warm engine, throttle plate open, fresh charged battery, use a remote starter, all plugs out, screw in type tester with a one way valve built in, then crank it till it hits highest reading, generally takes about 4 compression stokes to max out. Do this on all noting pressure, then I go back and squirt in some light oil, maybe a 1/2 teaspoon, take another reading. Look for even numbers wet and dry. IF you have an outlier, then do a leak down test, TDC compression stroke, pump up to about 100 psi with shop air, note leakage (should be no more than about 20% max) if more listen to exhaust pipe (exaust valve leaking) intake manifold (intake valve leaking) valve cover opening (rings leaking). Generally most of the leaking will be from the rings into the crankcase (valve cover opening). Very little if any should be heard from the exhaust or intake manifold (you can use a hose to ear connect hose to brake booster port on intake manifold for listening to intake).

as the plate pivots it activates two micro switches. they are located in a small plastic box on the throttle body in line with the rod that the throttle plate is screwed to. the on/off position is adjustable, one switch should be closed at idle, then off as throttle comes off idle, then another switch comes on again at about 2/3 throttle, so both switches are off at just over idle thru about 1/3 throttle. At least on the NA 280z efi.

oh forgot to ask, does the turbo model have the throttle plate position enrichment sensor (idle mid full switch mounted to the throttle body). On non turbos this adds fuel at idle. Its an adjustable series of micro switches that has a 3 prong plug. Small box on the side of the TB.

I doubt a running compression test will add any light to the issue. If you are worried about a loss of seal in rings or valves a leak down test will isolate. OR just do a wet/dry compression test. However all this seems moot since lifting the cap fixes the issue. a few things you should do a simple power test to see if #6 is causing a drop in rpm when disabled. do this with the cap tight vs loose since that is the title of the thread. It would seem to be the issue based on reading the plug, but the power test confirms. This will confirm the issue is #6 and the cap is the fix. If that works go simple, try switching a plug and wire with one that seems to work (cause a power drop when pulled). That will clear the wire and plug. do a wet/dry comparison of compression from a known working cyl to the suspect cyl, if the same that will clear the compression. Next try a new cap and rotor if the problem persist. If new cap and rotor have no effect, I would HIGHLY recommend you pop for the color tune. that will comfirm the fuel mix. That should show if the issue is a lean vs rich, swapping an injector should prove this out. The only thing that that I can think of (given the stated issue) re the loose cap deal is a poor air fuel mix that is hard to ignite coupled with a ign that is just on the edge of working with a lean idle mix. the color tune will show the mix and if its lean that maybe the issue. adding a spark gap to the cap maybe just enough to compensate for a poor air fuel mix and lets it fire. I would start with some brand new standard (cheap) ngk plugs, not sure about those fancy tip plugs (could be adding to the ign just on the edge of dealing with a lean mix). Pure speculation of course on all the above, but remote diagnosis is very hard since we don't even have a video to see/hear what is going on. Sometime there is a tiny clue missing like seeing a spark in the ign wires a night, or some other odd thing that gets overlooked.

would be an interesting mod if you could adapt the wide band readings into the AFM as a way of making the early systems into a closed loop. A small plus or minus voltage added to the wiper of the afm arm.

since I know you have done the research can you explain a few things? diff in "narrow band and wide band" where to mount O2 sensor. How to mount sensor. Before or after cat (if you have one, like I do on my 75 cali Z).

if its 16 ohms it may just be the high impedance coil on the injector, not designed to use the dropping resistor. The main problem I have is how that is fixed by the propped up cap, that observation points to a ign issue. IF you hear it clacking away that would tend to mean the coil is sufficiently energized, but that does not mean its flowing fuel. If its flowing fuel you should be able to see a wet plug. I really wish the lifting of the cap did not fix it, that really throws a metaphorical wrench in the works.