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Troubleshooting w/ Vacuum Gauge- where to go from here?


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Yes. The FPR is non adjustable. The only test is to compare the rail PSI to what it should be given the current manifold vac like your doing. Always there should be 36psi difference. If you have a vac pump like a mighty vac, you can attach it in place of the manifold and watch the rail pressure go up/down as you release/apply vacuum.

 

You would need to make sure the fuel pump is running during this test either by holding the AFM vane open (simulating airflow to the engine) or by jumper wire, or by pulling wire to starter solenoid & having someone hold the key in the "start" position.

 

BTW, if you just bypass the AAR with a hose you will always be in high idle mode. It's easier to just pinch the hose on either side with vice grips. That will take it completely out of circuit and you can test the rest of the system.

 

Also, I watched the video more closely and it looks like your getting around 30psi with 10" in the manifold. Those match so your FPR is probably ok. Other sources of rich condition are of course the AFM and/or the ECU. I'm doing a bunch of tests on AFMs currently. PM me if you have any questions.

 

Len

 

 

I do have a mighty vac. May test if all else fails to show 36psi diff.

I agree, about 9"-10" manifold to about 30-32psi.  I'll still check the FPR hose. 

Note taken on the AAR hose, I'll try the pinch method you described.

 

All of this won't be tested until tomorrow, so I'll report back with some info or potentially get her running smooth.

 

As for the AFR testing, I have poked around here for info and testing my own: http://atlanticz.ca/zclub/techtips/EFI&fuel.htm

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If you use a carb spray or similar product, you can find out if you have a vacuum leak in less than 5 minutes. This is a common method in the automotive field, that is still used to this day.

 

As i mentioned previously, you don't have to soak the engine or its components, to check or find leaks.

 

I'm not denying this and may resort to the spray technique if all else fails but will still try swisher sweet smoke first.

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As for the AFR testing, I have poked around here for info and testing my own: http://atlanticz.ca/zclub/techtips/EFI&fuel.htm

 

Yes.

 

That's Blue's site and has a lot of good information. He's more active on classiczcars.com, but he may be on here too. If you follow his method of setting the spring tension using a known mass (beer can on a string), the AFM should be pretty close. It definitely won't be so far out that the car runs massively rich.

 

The other usual suspect for highly rich is the coolant sensor connection. If that connection becomes corroded or disconnected, you will have an instant rich condition. I didn't bring it up earlier as you said you went through the EFI bible tests so you probably covered it already. The key is to measure at the ECU connector so you test all the wiring connections, not just the sensor itself.

 

Len

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Yes.

 

That's Blue's site and has a lot of good information. He's more active on classiczcars.com, but he may be on here too. If you follow his method of setting the spring tension using a known mass (beer can on a string), the AFM should be pretty close. It definitely won't be so far out that the car runs massively rich.

 

The other usual suspect for highly rich is the coolant sensor connection. If that connection becomes corroded or disconnected, you will have an instant rich condition. I didn't bring it up earlier as you said you went through the EFI bible tests so you probably covered it already. The key is to measure at the ECU connector so you test all the wiring connections, not just the sensor itself.

 

Len

 

I'm going to check the AFM spring tension as it may have been clocked and/or tampered with. 

I cleaned the coolant temp sensor, thermo, and pin connector on the coolant temp housing.  The thermo had corrosion on the female pins, going to re-clean them along with the coolant temp just to rule them out. 

 

I'm trying to pin down what started this in the first place, when I obtained the Z it started but ran slightly rough, it did die on and off.  After a test run, parked and upon restart it was belching white/grey/blue smoke out the tail with this bouncing idle.  The Z then got a fuel system cleaning, dumped the old fuel, lines cleaned, new filter, injectors cleaned and tested, new fuel and ran ok until it hit about 3,500 rpms when I felt a loss of power and hesitation. 

FI bible testing led me to the AFM issue, swapped with another potentially modified/used AFM, same result.  Bought a used unmolested AFM, untested, failed some of the FI bible testing.  Original which came with Z tested out to be the best from all the AFM's I have.  Next I started the inspection, cleaning of the FI harness and sensors.  Installed fuel gauge along with everything mentioned in first post and here I am.

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7 hours of work today on the following:

 

Cleaned thermotime and coolant temp sensors again.

Torqued down rocker cover and oil pan bolts....both had loose hardware....vacuum leak...eh?

Tightened down all intake mani ports.

New negative batt terminal.

Cleaned power wire to relay bank connectors and fusible links.

Checked FPR rubber hose, no cracks, holds pressure, flows fine.

Removed AFR to perform calibration check per: http://atlanticz.ca/zclub/techtips/afm/calibration/index.html

 

At 148mL's I get this:

 

IMAG0186_zpsc23360d7.jpg

 

Loosen the nut and start to turn the black wheel clockwise, almost 1/4 turn I end up with the wiper arm close to 1/2 way mark.  I found several other markings along the wheel from previous attempts to "tune" it.  This may have been why I'm running so rich, turning CW gets me back into the lean side.  I'll have to confirm with Blue, even though the wiper arm motion is smooth moving to the touch, it was not smooth to calibrate via can/water method. 

Also comparing this AFM to the unaltered exact internals AFM (used and failed initial FI testing) the tension of the wiper arms are close, but the weights at full turn are about 1/2" away from each other.  I believe the lock screw #2 has been touched as well.  Next time I'll check the voltage and sweep of the carbon trace.

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>

 

A lot of blowby is inconsistent with your compression readings. Can you do a leakdown test?

I'll have to source or buy one to verify.

 

After another look what I believe has happened is the A/C compressor has been leaking oil all over the place.  The A/C does work and blows cold.  This seems logical as there is residue all over the bottom of the distributor and surrounding area where the pulley spins.  I also checked under the compressor and found a coating of old oil and new pooling oil about to drip.  There should be 3-4.5 oz. in there, I'll have to pull it to confirm and or replace if I wan to keep A/C.

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All this...and no mention of a valve adjustment.

 

Last 8" Z I had, it went to 15 after valve adjustment...hot.

I'm getting there, it's in the plan.  Problem is I can't perform a hot valve adjustment bc I can't get a solid idle to even begin to warm the motor up, so I may have to go cold adjust.  So I first want to see if anything I cleaned or adjusted has made any difference so far. Thanks for the reminder.

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I'm getting there, it's in the plan.  Problem is I can't perform a hot valve adjustment bc I can't get a solid idle to even begin to warm the motor up, so I may have to go cold adjust.  So I first want to see if anything I cleaned or adjusted has made any difference so far. Thanks for the reminder.

 

You have your ENTIRE troubleshooting scheme backwards. The FIRST thing that has to be done is a basic tune up, and that STARTS with a Valve Adjustment. Specifications are give hot and cold, after overhaul you adjust cold and warm the engine to the point where you can recheck hot and go from there.

 

Block the radiator with cardboard, until it's up to temperature. It seems very strange you can't run the engine 5 minutes to get it up to temperature, but can run it long enough to make all the other adjustments you are doing.

 

You start it run it until it dies and repeat until up to temperature. Adjust your valves then move on. That is the basic first step in any Bosch System that used air flow control and was even more critical on the MAP-Based systems that preceded it. That critical nature was a primary consideration when it was decided to switch from MAP to AFC in the first redesign. Everything else stayed basically identical...but how it measured what the engine was doing was radically altered.

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One thing to remember, if you get it above 3500 rpms, the AFM is not in play there---the flapper is wide open and it should 'smooth out' --- it goes to the preprogrammed map at that point.

 

If it's still running rich, you are looking at FPR / CLT generally. That is the quick diagnostic checkpoint to eliminate AFM from the picture. I saw that originally it would not rev over 3500.... and that can be the case with CLT sensor. Usually if it's fuel pressure it's much more pronounced at idle, and less so as you proceed higher in the RPM range.

 

And above 3500.... it's all Preprogrammed on Engine Speed, and if the WOT contact is closed on the TPS, then it's a bit richer than less than 35% throttle opening above 3500.

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You can adjust the valves cold too...or at least check them cold to see if they are reasonable numbers. 2 thou less than adjusting hot.

 

The AFM looks to be why you were running so rich. Weaker spring = more vane movement with less air = more fuel for less air than designed.

 

Len

 

We'll have to see if I get to the valve adjustment tomorrow, have to check and see if I have a 17mm crowsfoot first.

 

I'm going to go through the entire test sweep of the AFM, I may still need to adjust the wiper arm of the vane if voltage is off.

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You have your ENTIRE troubleshooting scheme backwards. The FIRST thing that has to be done is a basic tune up, and that STARTS with a Valve Adjustment. Specifications are give hot and cold, after overhaul you adjust cold and warm the engine to the point where you can recheck hot and go from there.

 

Block the radiator with cardboard, until it's up to temperature. It seems very strange you can't run the engine 5 minutes to get it up to temperature, but can run it long enough to make all the other adjustments you are doing.

 

You start it run it until it dies and repeat until up to temperature. Adjust your valves then move on. That is the basic first step in any Bosch System that used air flow control and was even more critical on the MAP-Based systems that preceded it. That critical nature was a primary consideration when it was decided to switch from MAP to AFC in the first redesign. Everything else stayed basically identical...but how it measured what the engine was doing was radically altered.

 

Tony, here's the thing, you are correct.  It's even the first thing to do on page 4 of the FSM Engine Tune Up. :bonk:

 

Unfortunately, I'm going off of what the previous owner described to me which wasn't much other than the motor was rebuilt and the head gasket replaced (date unknown).  For all I know with it's 180,000 approx miles the block was bored out and new pistons installed upon said rebuild.  I did drive the car home over 3 hours, it didn't overheat and ran fine at highway speeds, I kept it under 3,000 rpms as when I went on it's test drive there was a hesitation/sputtering over that rpm.

If it's a valve adjustment/check which should have been performed early into my troubleshooting then I'll get right on it after I complete my retest of the AFM (not starting the motor). 

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"Tony, here's the thing, you are correct."

 

Well, I give you kudos for not getting PO&B over saying that! LOL

 

Remember if the head had any work, and they put new valves in, they tend to recede at a VERY fast rate for the first valve adjustment period. Some builders will run the engine on the dyno, then readjust valves. If it was road-broken then maybe after 500 miles, with the oil change, and then again at the next oil change (3000 miles) -- depending on what kind of recession rate they see, they may leave it for regular interval afterwards (30K miles) or adjust it again until the recession (change in set value from last adjustment to as-found) levels off. Once they are 'beat in' they can go quite a long time. I don't want to say this, but I actually realized my 260Z has gone 110,000 miles since I last adjusted the valves in 2001 when I took my son to the ZCON in Canada. 

 

Maybe THAT is why I've been having the problems I have been having...

 

It happens to all of us... doing a valve adjustment on 'The Blue Turd' is on the top of MY list when I return to the USA in April!

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Ran out of time to perform a valve adjustment, took me half the day to source a 27mm socket for the crank pulley and a 17mm crowsfoot.

 

But I did test the AFM, results:

 

Measure the resistance from the high side to the low side of the pot/copper trace. (Pins 8 and 6). It should read ~180ohm

Mine read: 227.0 ohms

Measure the resistance across the "standard"/"Reference"/"Control" resistor. (Pins 8 and 9). It should read 100ohms

Mine read: 130.0 ohms

Measure the resistance across pins 7 and 8 while moving the flap. It should change. (though it may be jumpy)

Mine: Changed and mildly jumpy

Repeat this but between pins 6 and 7 while moving the flap.

Mine read: same as last test
 

Measure the resistance of the thermal sensor. It should read 2500ohms +/-250ohms@ 68°C

Mine: Passed

 

So are these results considered passing or are the impedance's too high for the first 2 tests?

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