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charliekwin

Project Boondoggle (or, so I went and bought a Z!)

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Nice! Spent the day doing basically the thing to my tank. Haven't started cleaning the inside uet. Next weekend.

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The smog testing adventure continues.  Took it in for a pre-test today and failed again with similarly awful numbers.  Good news is that at least the EVAP leak was fixed by all the work on the fuel tank.  Also had a new cat put on, so at least that's legal, but not fixing my emissions issues.  Plugs, air and fuel filters as well as a couple hoses have already been replaced.  It runs very rich, which the sniffer confirmed as well.

 

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Earlier in the week I checked the coolant temp sensor, and the resistance across the terminals looked pretty good.  The connector looked bad and fell off when I touched it, so I replaced that as well, but apparently that wasn't the quick and easy fix I was hoping for.  I'm working my way through the bible now, starting with checking the fuel pressure.  I know the AFM has been opened before (it's been re-sealed), and knowing how other work on the car has been handled, my suspicion is that it's wildly out of adjustment.  Any of the gurus out there have additional suggestions?

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Earlier in the week I checked the coolant temp sensor, and the resistance across the terminals looked pretty good.  The connector looked bad and fell off when I touched it, so I replaced that as well, but apparently that wasn't the quick and easy fix I was hoping for.

 

This here is your main hurdle.  You have to measure and get real numbers at the ECU connector.  And there is almost never a quick-easy fix.  Just a collection of small fixes that add up.

 

Those numbers aren't that bad.  Mine were similar, but they only check idle up here.  I lowered my fuel pressure and made some other adjustments.  But I have a modified system that allows that.  

 

The first three things that I would do are:  measure resistance across the cooling circuit pins at the ECU connector and compare it to the chart, measure fuel pressure with and without the vacuum hose connected and with the engine running, and examine the AFM gear with a magnifying glass to see if you can find the original glue blobs and put it back to where it was.

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Thanks for the insight Zed Head.  I checked resistance at the ECU and the numbers are at least in the right ballpark.  I have to hunt down a thermometer to get actual coolant temps and will check again to confirm, but considering the ECT is $13 and an Amazon Prime item, I may just get a new one.  Engine temp gauge never seems to go more than about an 1/8" or 1/4" past the 120 degree line, which -- if that's low -- I guess could also point to a problem with the sensor (or a stuck thermostat).

 

Fuel pressure gauge is also on the way after a goose chase in which I learned that none of the major auto parts stores carry those.

 

And finally, I cracked open the AFM, which was...interesting.  I've done some looking around, and I think I might have a 280zx and/or a remanufactured unit, because the counterweight doesn't look like any of the pictures I've seen of other 280z AFMs.

 

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Fingering the AFM helped lean it out, but didn't seem to make it otherwise run much better.  Pushing it towards the rich side immediately made it worse so I must be on the edge with the mixture right now.  I won't make any adjustments to the AFM until addressing the other things, though.

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 I have to hunt down a thermometer to get actual coolant temps and will check again to confirm, but considering the ECT is $13 and an Amazon Prime item, I may just get a new one.

 

 Engine temp gauge never seems to go more than about an 1/8" or 1/4" past the 120 degree line, which -- if that's low -- I guess could also point to a problem with the sensor (or a stuck thermostat).

 

Fuel pressure gauge is also on the way after a goose chase in which I learned that none of the major auto parts stores carry those.

 

And finally, I cracked open the AFM, which was...interesting.  I've done some looking around, and I think I might have a 280zx and/or a remanufactured unit, because the counterweight doesn't look like any of the pictures I've seen of other 280z AFMs.

 

 

Fingering the AFM helped lean it out, but didn't seem to make it otherwise run much better.  Pushing it towards the rich side immediately made it worse so I must be on the edge with the mixture right now.  I won't make any adjustments to the AFM until addressing the other things, though.

If you measure before you drive it, everything should be at room temperature.  Often it's not the sensor but the 6 connections between it and the ECU circuitry.  Each one can add a little resistance, showing a cold engine to the ECU and causing added fuel.  Clean all of those connections.

 

The temp. gauge doesn't use the coolant sensor.  It's separate.  There's a sensor and a sender.  But a cold engine will be a big problem.  Often people have overheating problems and remove their thermostats.  A new Nissan thermostat would definitely be worthwhile.  Your local dealer might have one, or Courtesy Nissan.  Nissan quality is worth buying for that part.

 

Are there numbers on the AFM, either the cover or body?  A11-xxx-xxx.  That will tell you something.  Idle circuit is separate from running circuit, there's a switch on the throttle body.  So fingering the vane will only show gross problems.

 

 

I'd focus on getting the engine hot first.  You can't pass if your ECU is adding fuel for a cold engine.

 

I think that 78 is A31-604-000 for the AFM.  And you're right, that AFM does not look like my old 1978 AFM.

Edited by Zed Head

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I agree with the above. Those numbers don't look that bad.

 

You know there is an idle mixture screw on the AFM don't you? It allows for more or less air to go around the AFM vane hence affecting mixture under low lower load (idle and light cruise) conditions. Before you go tweaking the AFM, you might want to try opening that idle mixture screw up a little. Counterclockwise for lean. Clockwise for richer.

 

Adjust the idle mixture screw while you have the sniffer up the pipe. There's some description in the manual about how it should be adjusted. IIRC, you're looking for CO numbers which will indirectly tell you mixture.

 

Sorry if I'm telling you stuff you already knew, but stating the obvious is part of my contract.

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The quick recap on the last week or so, in which little may be going my way toward the end.

 

First the good stuff.  My current garage work/storage area has been pretty pitiful, so I got a little something for my birthday to help with organization.  Thanks dad!  Also, the battery ground was in terrible shape, so I dug up some old 0 AWG welding wire and some lugs I had leftover from the audio install in my G and redid that.

 

And that's about the end of the good stuff.  Moving on.  When I went to replace the thermostat and coolant temp sensor, I found that the housing had been cracked and epoxied back together with the same stuff that was used on the fuel tank.  The housing is discontinued, but it doesn't seem to leak, so I guess it stays for now.  A previous owner had also removed the thermostat entirely.  Replacing that and the sensor seems like it's getting the engine up to a better temp and (based on smell and fingering the AFM) I think it's leaned out a bit.

 

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Now for the ugly.

 

I ran a compression test.  From 1-6: 75, 70, 55, 70, 70, 65 psi.  I think I need someone to hold me.  I've never done a compression test before, so there's a possibility I did it wrong or maybe the gauge is off, but those numbers seem outlandishly low.  It puts out smoke at higher (~4k) RPMs, but seems to pull pretty well.  I put a bit of oil in #5, which bumped it up to 100, and went on to valve adjustment.

 

After pulling off the valve cover, I found a whole mess of sludge up there.  I'm tempted to try to clean it up, but my gut says it might be better to leave it alone so it doesn't get dislodged.  Thoughts?  I'm going to re-run the compression test after the valves are done and hope to see better numbers.

 

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Did you use an adapter with your pressure gauge?  They add a lot of volume and will lower the numbers quite a bit.  Better to take the numbers on a warm engine also.  Plus, if the oil is gas-thinned from running rich you'll get a poor seal.  Cylinder pressure tests are mainly good for comparing quality between cylinders.  You're looking for consistency.

 

The 30 psi bump with added oil and the sludge do suggest high miles and wear though.  But you'll probably be able to get it to run well and pass emissions, it might just burn some oil and smoke a little bit.  The valve adjustment might have a significant effect, since it's possible it hasn't been done while all of that sludge was building up.

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I used the pressure gauge that Pep Boys loans out (http://www.pepboys.com/parts/tools) and did check while the engine was warm.  With the exception of cylinder 3, they all test pretty close, so I won't fret too much about the low numbers, but the increase after adding oil is disappointing.  If I can still pass smog with the engine in this shape, I can live with it for a while and swap or rebuild sometime later.

 

Valves (somewhat surprisingly!) were well-adjusted,  Only two of them needed adjustment, and both were only off by 1 thou.  What of the sludge?  Leave it or clean it?

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Doesn't the intake have to be open somehow? On carbureted carbs I believe you hold the throttle open so the butterflies don't restrict the intake of air.

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If you have a shop vac you can rig up a hose to get in to the crevices.  I would just worry about dropping a chunk of sludge where it could do some harm, trying to spoon it out.  It's not going anywhere otherwise, unless you plan to hit some bumps at high speed.

 

My old engine had worn valve seals that leaked oil in to the intake runners.  If you're looking for work, new seals might clean up emissions a bit.  I still passed though with my old seals.

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I wouldn't try to remove the sludge, but that's me. If you dislodge some of it could cause issues.

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Sludge stays, then.

 

Doesn't the intake have to be open somehow? On carbureted carbs I believe you hold the throttle open so the butterflies don't restrict the intake of air.

 

I had my wife floor the gas while she cranked it.  I think that's good enough?

 

My old engine had worn valve seals that leaked oil in to the intake runners.  If you're looking for work, new seals might clean up emissions a bit.  I still passed though with my old seals.

 

More work?  I'm just hoping to get one project finished without it creating two new ones!  :LOL:

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Turns out that Pep Boys' crummy loaner was missing an o-ring, which explained the miserable compression test.  For $19 out the door, I got my own from Harbor Freight.  Much more appropriate results the second time around (bottom set of numbers is with some oil in the cylinders), at least in the neighborhood that I'd expect for a 37 year old motor:

146 -- 145 -- 148 -- 145 -- 141 -- 145

160 -- 165 -- 171 -- 182 -- 175 -- 162

 

The plugs, from 1 to 6.  I replaced the plugs maybe 6 weeks ago, so they have a few hours and barely any miles on them.  Obviously I'm running rich, and 3, 4 and 6 look like it.  1 looks the best.  I'm not sure about 2 and 5?

 

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And, FWIW, here is a video of the car idling.  There's a tick that I'm not sure if it's supposed to be making, and it has a kind of ...syncopated... sound to it, more easily noticeable in the exhaust note.  

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Much better numbers. I would think with the first numbers you had the car would have barely moved

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A big thanks for all the help! The official test is wrapping up, but now I can finally get it registered and titled and actually drive the thing. Until it gets taken apart, that is It's beer time!

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Congrats! And those numbers look fantastic!

 

I saw your other thread where you throttle position switch was out of adjustment. Glad that was the only serious issue. That was an easy one!

 

So now that you got the WOT switch working properly, can your nose tell a difference? Is it less stinky?

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Absolutely. The smog tech actually said he thought it would pass right after I pulled in to the shop, since it smelled so bad the first two times.  (Hat tip to the tech, who was nice enough to drop the $30 pretest fee today, which was a nice gesture.  He was asking questions about the car and what I'd done to it; I think he liked having a customer he could talk shop with.)  Plus, no more headaches after being in or around the car for 10 minutes. Carbon monoxide is no joke!

 

I think all the changes actually ended up leaning it out about one click too far, so I'll play with it a little more this weekend to see if I can get it dialed in "good enough" for now.

 

Also decided to wait on interior for now in favor of re-doing the suspension.  It needs it.

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Nice.  Even when the things that should work, do work, it's still a surprise.  Those are low numbers.

 

Consider the coolant circuit potentiometer tweak for adding a little bit of fuel, if it's lean.  Many of us use it,

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Absolutely. The smog tech actually said he thought it would pass right after I pulled in to the shop, since it smelled so bad the first two times.  (Hat tip to the tech, who was nice enough to drop the $30 pretest fee today, which was a nice gesture.  He was asking questions about the car and what I'd done to it; I think he liked having a customer he could talk shop with.)  Plus, no more headaches after being in or around the car for 10 minutes. Carbon monoxide is no joke!

 

I think all the changes actually ended up leaning it out about one click too far, so I'll play with it a little more this weekend to see if I can get it dialed in "good enough" for now.

 

Also decided to wait on interior for now in favor of re-doing the suspension.  It needs it.

 

That cracked thermostat housing would be my top priority. Epoxied aluminum + so cal summer heat= not good.  You can pick up a good used one or a new one on ebay.

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Small update, here in the middle of re-doing the whole suspension.  Took both front and rear off the car two weekends ago and found some good and bad.

 

Bad: one each of the tie rod ends and ball joints had torn boots, so they're all getting replaced.  All four shocks were completely blown; no rebound at all.  The strut mount insulator bearings were covered in some kind of severe nastiness.  Spindle pins were in bad shape, but at least that made it easy to beat the heck out of them.

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Good: seems like all the bearings are in good shape.  A previous owner had already replaced most of the bushings fairly recently, so getting those off proved easy.  Aside from consumable parts like the ball joints, everything else was actually in pretty good shape and I didn't have to facepalm once when taking things apart.

 

After getting everything apart, it's been a lot of cleaning and paint prep.  Started with a wire wheel, then made my first go at media blasting with a $20 siphon-feed gun.  Not really knowing what I was getting into, I made this -- uhh...crude -- little "setup" thinking it might keep the mess down.

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It didn't.

 

So I did a little scrounging around the house to come up with something a little more sophisticated.  Still made a mess, and wasn't without some difficulties, but it got the job done well enough.

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Still have a little cleaning up to do, but hoping to get prep finished by this weekend so I can move on to paint and then get everything put back in two weeks.  My stack of parts going in: Vogtland springs and Stagg shocks, Suspension Techniques sway bars, poly bushings, tie rod ends, ball joints, and a bunch of miscellaneous hardware.

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Only thing I'm not sure about is how to deal with the rear struts.  Blasting and then painting the whole assembly seems like it would be a bad idea: too likely for abrasives and other stuff to get where it shouldn't be and muck up the works.  I supposed I could remove the rear hub, but everything I've read makes me think I never want to do that.  So for now, I'm planning on just cleaning and painting the strut tube and leaving the rest -- rough thought it may be -- as is.  Is there a better option?

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Really enjoyed reading this thread, keep up the good work

Edited by Red7

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Great work Charlie!  I love your DIY blast cabinet made from the Rubbermaid tote.  On your question about the rear hubs, if the bearings are quiet and feel good and no grease is seeping out of the seals I would say leave them be.  You can clean up everything pretty good with a wire rotary brush.  If you do have to take the hubs apart its best to use a press as to not damage anything.  Others have done the job without one but since they are off the car and if they really need attention then do it now and do it right.  Check out the link to the resto thread of my '72 240z in my signature.  I did this on my car and you can get an idea of what is involved along with checking out search results on the topic.

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Thanks for the comments!  For a grand total of $0 + a disapproving look from the wife when I pilfered the glass from a picture frame, the Rubbermaid rig more than paid for itself.

 

The bearings and seals in the rear hub all seem fine, so I'm pretty reluctant to try and break in there, but I might take the same route you did and hit everything I can with the wire wheel.  I remember going through your thread a few months back and yours came out looking quite nice.  Anything would be an improvement over the mess it is now, and I know it'll bug me if I leave them alone after going through the effort to clean up everything else.

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