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paul vixie

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  1. looking for a new (really) wastegate actuator for my 280zxt

  2. ok so there were leaks but not in the vacuum side. a new PCV valve didn't solve it, and there were no leaks in the PCV hose. i ended up having three problems, and have fixed two and worked around the third. i still need a little advice if i havn't bored everybody to tears yet. 1. i had a boost leak at the coupler (output side of turbo). the rubber was cracked in a way that only leaked under pressure. at ~250K miles on factory rubber, it makes sense that it would hold pressure for a while and then disintegrate, the car had been parked in a (hot) field for ~10 years before i bought it. the fix was to buy a three foot chunk of outrageously expensive 2-inch radiator hose and replace the rubber in the coupler. my son (ineptitude01) also took a few inches for his 82 ZXT. if anybody else wants a chunk to replace the rubber in their coupler, send me a self addressed return mailer and it's yours. with a new coupler, i got my boost gauge up to ~200mm/hg. still well short of the red zone but higher than it had been in months. so, a partial fix. 2. the waste gate spring is weak. it tested at 8psi with a bicycle pump, so i'd rule it out, but thanks to goodoldjam and junglist i was inspired to put on a manual boost controller set for 10psi. this immediately got my boost gauge up to ~350mm/hg where my popoff valve started singing to me. (see #3 below.) i dislike the MBC behaviour, it gives a cliff-like tail-off for boost, i prefer the asymptotic tail-off i had before my spring crapped out. again, factory spring, 250K miles, 10 years in a field, i'm ready to believe that i had a couple good weeks before deferred metal fatigue set in on my wastegate actuator spring. my son says his electronic boost controller gives better tail-off than the manual boost controller, but i really want to run it stock, which means i need a new wastegate actuator. i'd love to know where to buy a new one that will fit the stock 83 ZXT, so that i can take out the MBC. 3. the popoff valve, as mentioned above, was fluttering open at around 350mm/hg on the boost gauge. on the hope that i'm done backfiring into my intake, i replaced the popoff with a 1-inch NPT plug. now i'm getting a solid 400mm/hg on the boost gauge, which means i had more deferred metal fatigue in my popoff valve. i'm not concerned about the popoff like i am the wastegate, but if there's a source for replacement popoff valves i really would like to install one and get it back to "stock config". thanks hugely to all who advised me on this. the problems turned out to be simple like you said, just requiring patience and determination.
  3. and indeed, all is now well with engine timing wrt the TPS. thanks for all who contributed material to these threads.
  4. Unless something is leaking during boost and you can't hear it. assuming that could happen at such a massive are volume and velocity as the output of a turbo, and assuming that it was somehow a one-way leak such that i could lose boost but still have compression braking... how would i go about testing for it? It's also seems strange that it happened right after the Marvel Mystery Oil my theory on that was, the turbo shaft had been held in place by oil-jello that the marvel mystery oil broke up. however, i can't imagine a shaft bearing problem that could result from such a sequence that wouldn't also result in a lot of shaft play -- there's none. so, at this stage i'm calling the marvel mystery oil a coincidence. Have you checked the j-pipe connector boot or the intake arm to see if they have any rips or tears? Do either of them compress under engine load? no rips, no tears, no compressibility with my hands. but wouldn't intake leaks also keep the car from having compression braking? You should also check the pop-off/bypass valve on top of the intake manifold to make sure its not stuck open and can open/close on its own. i'm able to pull it up but it closes pretty firmly. if it was opening it would be all-at-once and would make the characteristic "pop" "whoosh" sound, i think. but this is worth checking into. i'll try some nylon tie-wraps on it to hold it forced-closed, and see if that changes anything. good idea, thanks. Also, make sure your PCV valve & lines aren't clogged. i never thought of the pcv. will do, thanks. see also http://www.zcar.com/forums/638061/ecu-wont-go-closed-loop-mode-280zxt which suggests that an EGR diaphram leak is worth visually checking for.
  5. i bought a junk yard head just to get the lifters. i don't know how many of them are good yet. but, see this sticky: http://forums.hybridz.org/index.php?/topic/50067-p90a-head-ticking-what-to-do/page__hl__cleaning%20hydraulic%20lifters which explains that you have to disassemble each HLA, soak them in chem dip, wire brush their innards, and then reassemble them while submerged in oil, if you want the ticking to stop. i added a comment at the very end telling of my own experiences with this approach, which were extremely positive.
  6. there is no difference between the intake and exhaust HLA's. yes, the oil stays in the lifters, if you reassemble them inside oil. note, i added a comment to that other thread (http://forums.hybridz.org/index.php?/topic/50067-p90a-head-ticking-what-to-do/page__hl__cleaning%20hydraulic%20lifters__st__40) since only the smaller piston (with the ball check valve) and its spring have to be put in while submerged in oil, the top piston and the hat can be put in dry.
  7. the spring is strong. i can force it with a screwdriver while it's attached, and it takes some real effort.
  8. yes, i disco'd the actuator arm from the wastegate arm and got completely free movement on the arm from full-open to full-shut, with a nice strong clinking sound and a positive all-at-once landing at both ends of travel. of course i didn't see the innards so there could just be a hole in the flapper or pieces missing or it's not seating correctly when closed -- sure feels right though. while i had it all apart i pressure tested the wastegate diaphram, it moves at ~6PSI like it should, and has a good spring inside. i'm starting to wonder if my catalyst is plugged somehow, since i seem to remember hearing more turbo-spool noise when the whole thing was working better. i guess i'll disco below the downpipe/O2 and just play it loud for a bit and see if i can get the old/good boost that way? trouble is, the more i take this exhaust apart, the more busted studs i gotta deal with. anybody got a stock downpipe for sale? the one i've got in now has stripped O2 sensor threads, my "spare" has some busted and stripped/rusted studs stuck in it. my theories are that if i had leaks in the wastegate pressure lines i'd've blown up the engine by now, and if i had leaks in the intake large enough to vent turbo pressure, i would hear that happening, and i would not have such strong compression braking when going downhill in gear. if these theories are of low quality then please please please shoot them down.
  9. 1983 280ZXT T-5 2+2 stock, ~245K miles. When I got this car it boosted to ~5 with good neck-snap. (Had to replace all vacuum lines etc, it was a barn find, 10 years out of reg.) Eventually I put Marvel Mystery Oil in, thought it was an engine cleaner, but it looks more like STP ("honey"). That weekend my turbo started boosting only as far as ~2, and no neck-snap. I've since checked shaft play (none, and compressor wheel spins freely), waste gate (moves freely, and actuator arm is not too long), manifold leaks (none), and I just tonight cleaned my lifters (I think I had an I5 until tonight, now it's definitely an I6) and cleaned my plugs. I'm looking for other tests I can run or things I can try. I wouldn't mind finding a replacement turbo (note, I want to keep this car stock, so a disco potato isn't in my future, and note, I'll be wimping out and having the exhaust shop do the turbo swap due to the number of studs I expect to break off in the process.) But other than "your compressor wheel isn't spinning as freely as you thought" or "you must still have a vacuum leak somewhere", I am looking for other tests I can run or things I can try. I eventually ran some engine cleaner through, to get the Marvel Mystery Oil out, and I'm running VR1 20/50 ZDDP. Themostat's new, temperatures are good, ECCS harnesses (ECU and engine bay) have all been cleaned well, CHTS is good, timing's good, TPS is good. Help?
  10. Resurrecting this thread again after six years. I followed these instructions, mostly, and got spectacular results. I'm starting to think that Nissan made a mistake in not including rebuild instructions on these lifters -- FSM says if they go bad you replace them, but after cleaning a whole set from a Pick&Pull P90A, I can't imagine how they'd wear out. This thread should not just be sticky, it should have been in the FSM all along. The use of a Sharpie is pure genius and works perfectly, I would never have thought of this. My read on this is, there are three failure modes for this lifter. Ball check valve stuck open or stuck closed, air bubble below the ball check valve, or scoring on the piston or cylinder. The first two are amenable to cleaning. The third one would have to be really bad before you'd throw a lifter away. They don't bleed down when the motor's off. The ball check valve says, once the oil's in, it's in. This is a terrible design, since with no bleed-down and no flow-by, the oil that's in there is from the factory or from the last time you cleaned the lifters. In my case it was old and carbonized and there were some stuck-open and jammed ball valves from the oil-carbon particulates. The guy who told me to try engine cleaner was nuts -- there's no way for it to get in there. I did not use a spring compressor since there was no way to get it in there with the head on the car. A screwdriver, using the cam for leverage, and careful not to go metal-on-metal on the shiny places, got the springs down far enough for me, all 24 times (12 out, 12 in.) I did not fully assemble them immersed in oil. I put the spring in after cleaning the barrel with Chem Dip and a round wire brush, and then immersed the barrel+spring in oil, got the bubbles out, and then put the smaller piston in after cleaning it also in Chem Dip and clearing the particulates out of the ball valve. The small piston stops when it reaches the oil supply hole in the barrel, since there's nowhere for the oil to go and it doesn't compress. So then i took it out of the oil bath, dripped and wiped off the excess oil, put it down on the bench, and put two small allen hex keys into it. One hex key was in the center, to release the ball check valve, and one was off to the side, so i could compress the bigger spring under the smaller piston. This was the only tricky part: letting the ball valve close before letting the piston off the spring. With that dance, the larger piston went in far enough that the hat clicked into place easily. I have a junk yard P90 head that I'll put in at some convenient time. Meanwhile I'm extremely grateful to all of you for this forum and this thread, I've now got low end torque again, I think I had an Inline 5 until this evening. THANKS, ALL.
  11. according to the 83 FSM, the CHTS has lower resistance at higher temperatures. therefore, unplugging it should make the ECU think that the engine is cold (infinite resistance). when the engine is cold the ECCS is supposed to enrichen the fuel (longer injector pulse width) and also advance the timing. noting that the FSM also indicates that the TPS's "idle" signal will cause the timing to advance and that at least one person recommends unplugging the TPS when setting timing but that the FSM (and Haynes) do not mention this, i suspect that there are a lot of badly timed ZXT's in the world, starting with mine, which i'm going to go out and re-time now.
  12. i found this other thread where timing retard was discussed and followed up there with some information i found on another forum. i'll post followups there not here. this topic should not have been created, i hadn't searched carefully enough on the timing retard question, sorry all.
  13. on another thread i asked this same question and eventually went page by page on the FSM and found that there is a timing advance (of about 10 to 15 degrees) when the TPS indicates that the car is idling, or when the CHTS indicates that the car is cold. over in zdriver, nismopick said that the timing should be set with the TPS disconnected. this means if you set timing with the TPS plugged in you're doing it on an advanced basis, and when you lose the "idle advance" coming off idle then it'll look like retard. i'm going to get out there and set my timing with the engine warm, having cleaned the CHTS and knock sensor contacts, and set the base timing without the ~10 degree advance that gets added at idle, and i'll let you know how it goes.
  14. so, on ecu models like the zxt, advance is electronic, and there's a throttle position sensor, and there's one advance map for "when you are at idle" which is when the TPS reports that there's no pressure on the accel pedal, and another advance map for "not at idle but not wide open" and yet a third advance map for "wide open". the timing on this car is set at idle. i could unplug the TPS at which point it would still think i was at idle. i could short the right pin to get it to think i wasn't at idle and then set timing from that but there should be no difference between the idle map and the bottom of the non-idle non-WOT map. if i set physical timing using the bottom of the non-idle map then i'll be advancing ~15 degrees, and then when it goes back to the idle map it'll be at ~40btc. i used to own and work on vacuum based cars. i liked them, and the points and the rest. the behaviour i am expecting is, begin to advance once the rpm's go up, and not just because my TPS reports a non-idle condition while the rpm's are still ~600. for this car to move from ~24btc to ~10btc just because i'm changing from the idle map to the nonidle map (based on TPS, not RPM) means it's retarding it on purpose. as i said in the base note here, i unplugged the detonation sensor and saw no change in behaviour. therefore i am mystified. no ecu car and no vacuum advance car i have ever worked on has retarded timing while coming off idle.
  15. in researching why my car (280zxt 1983) won't boost past ~2 like it used to, i noticed that the timing jumps forward immediately when i come off idle. that is, i'm watching the timing, it's right at 24btc where i set it, but then as soon as i touch the throttle -- just enough to budge it, not enough to change the rpm's at all -- the timing jumps up to ~10btc. then as i press on and the rpm's increase, it advances normally. by 4000rpm it's way past where i can see it. on a hunch that it might be seeing detonation and thus retarding timing to save my ass for me, i disco'd my detonation sensor. no change. i've seen this now on two ecu's so if it's an ecu problem it's a hell of a coincidence. i can't think of any reason the car would retard timing as soon as the tps indicates that i've come off idle. anybody got a checklist? is this normal? needless to say there is hesitation when i come off idle. i can feather the pedal to get around it, but it's not right, and it's gutless too.
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