1977 280Z Bouncing speedometer

[Zed Head]

It's very common for them to get stuck or only move a smaller amount than they are supposed to.  Your symptoms match a stuck AAR.  Many people just remove it and use their eye to see if it's working correctly.  You can connect a battery to the terminals and watch it close.

[240zadmire]

2 questions

- AAR cannot be rebuild.  Only new if available or good used one

- if I bypass the AAR and connect the hose where my finger is pointing to, to the location where AAR is currently hooked up, I should have high idle no matter if engine is cold or hot?

 

regards

[Zed Head]

You can adjust idle speed with the idle speed adjustment screw on the the throttle body.  The AAR is there to hold the idle speed up just long enough for the engine to get warm enough to raise the idle speed.  It's a convenience. 

Back in the old days we used to sit in our cars (any car) and rev the engine until it would idle on its own.  If it was extra cold out we'd remove the air cleaner and hold our hand over the carburetor to get more fuel pull while someone else cranked the engine in order to start it.  If we flooded it, we'd hold the throttle wide open and crank until the battery died.  Then we'd get some friends or strangers in the vicinity to give us a push for a jump start.  

[240zadmire]

You painted a very vivid picture.  I can related somewhat.  I had my car die on street couple of time not because flooded and cranked till out of battery. It die because of run out of gas and aware of it.  I tried to drive as fast as I can to the destination I wanted to go... either to school or back home and Good Samaritan would help push into some parking lot.  Go about my business if school was the destination and borrow literally a dollar or 2 as gas was like 87 cents a gallon.  Walk back to the car with a can of gas and keep on driving.  There was no cellphone and beeper was just a hot thing.  Who can afford those anyway.  Best days, I tell you best days of my early adult life.

 

regards

 

[240zadmire]

How wide open does the AAR need to be at room temperature? Does it needs to be able to see through the holes?  Not necessary the whole hole but a crack open that can shire light through?

regards

 

[240zadmire]

Hello

 

pull it off, put in freezer for few minutes, it opened up wide. Blow air with virtually nonresistance.  Figure at least mechanically still good.  Use half bottle of brake cleaner.  Carb cleaner probably better/quicker but all I got at the moment.

broke off the hard silicone on the adjusting screw. Feel the movement as unscrewing it. Got to be able to adjust it.  Gently put a flat screw driver to the open area to see if the blade can be move and it does.  Move it a little to the side.  Tighten up.  Blow air.  Air blown by freely.  Energize direct to 12 volt battery.  A couple of minutes later. Blow air to it and with great resistance.  Left on the floor with ambient temperature for 20 minutes or so.  Blow air to it with ease.  Hook it up with high expectation rpm should be high immediately and it did.  She climbs to 1500rpm with high fan for about 1 minute.  Fan lower to same engine noise and engine runS still high 1500rpm for a minute or 2 and gradually lowering the rpm to 950 or 950.  I’m stoke!

She idle beautifully.

ill let her test for rest of the night and she’s should behave nicely tomorrow morning.

this is a fun journey.  I have other quirky nuances here and there and will post up soon

 

thank you all for the help and guidance!

 

below are the photos close and open.  Though slightly but behind the door, the bimetallic probably do some awesome magic in there

 

Edited August 13, 2020 by 240zadmire

[240zadmire]

Want to update the progress so we can close the issue.

She rev up the RPM to 1500 right away without hesitation.

Your theory of sticking AAR didn't open is indeed correct.  Car keep thinking it has enough air but in reality it was suffocate when cold.  I'm a happy camper ?

one down, many more nuances to go.

Thanks for all the help and this issue is closed.

 

regards

 

[240zadmire]

Greeting folks,

Got a chance to re-lubricate the speedometer cable and other things bother me as the mileage doesn’t seem match with the google map.  Got curious, drove different car with same route and my minivan milage agreed with what google map.  My Z is short a few miles.  On top of that, the speed, mph is ~5 miles slower.  I download the app from Apple store to measure….

 

got curious, did the 10 tire rotations as well as the one complete rotation and see where the shaft pointed to… both agree to be shy of 17 revolution and 3 o’clock mark.  So the diff ratio is about 3.36.  However, the stamp on the r200 gear is 39-11 as shown in the photo.  Moreover, the speedometer pinion seem to be incorrect.  It is red and 20 teeth.  
 

I would think my 5 speed and r200 with the info above should be a 17 teeth, black color pinion.  What do you think?
 

and btw, the transmission seem to be an early s30 rather than the 5 speed 280zx

 

regards

 

 

[cgsheen1]

Agree. The stock R200 in a manual transmission, non 2+2, would be a 3.545 which should use the black speedo pinion gear. Your transmission is early, but even the ZX transmission would use the black pinion gear.

[240zadmire]

Well, I ordered a black version of 17 teeth and guess what? It is much smaller than the red one.  Take a look at the photos.  Is there more than one black 17 teeth?  The black I received is about 20mm vs 24mm wide for the red one.

please advice.

 

[Yarb]

The spline size won’t change. The diameter of the cog is directly proportional to the spin rate. Someone please chime in If I’m off base here.

[240zadmire]

Seem like my 5 speed is from a transmission type “B”.  If I turn the pinion housing upside down, then the gear bites the internal worm gears.  For testing, I “manufacturing” a lock washer to hold it in.  The interesting thing is the speedometer is about 3-4 mph faster.  So, I’m having a dilemma.  The original pinion was 20 teeth and odometer is ~5mph slower.  The 17 teeth pinion is ~3-4mph faster. 
I either need to get a blue, 18 or white, 19 teeth.  
the numbers stamped on the r200 shoe that my ratio should be 3.54.

 

what do you guys think?  18 or 19? I’m leaning toward 19