I did a bit of browsing but I couldn't find anything that helped me specifically so just looking for some insight.... Just picked up a gorgeous '85 with a 12A and everything is perfect on the car except for 2 things. 1) The car needs to have the choke pulled out for like 8 minutes or more until the car gets warm enough to stay idling, when it IS warm though it idles at like 500 rpm perfectly which is ridiculous cause my other first gen I can't seem to get under 1000 rpm idle. So i'm wondering if it's just a choke adjustment issue. the carb is in great condition, I've never seen a Nikki in such good shape. And issue 2) When I drive over 40mph I get fairly bad vibration in the back end. I think its the passenger side rear bearing but I'm not sure. There's no grinding, just vibration. And when I slow down you can hear a mild tick in the back. If it is a bearing how difficult is it to change, I've never had to change one on my other FB.

 

The "choke problem" sounds to me like you may have a stuck-open (or removed) engine thermostat, which is preventing rapid-enough warm-up.

Choke retraction is controlled by a thermodetector on the water pump; it releases the choke-hold magnet when the water temp is warm enough; on my car, it's reliably about 3 or 4 minutes, and right about when the temp guage hits the bottom of the 'normal' range scale. If your main thermostat was removed or is failed open, your engine will take a lot longer to come up to proper temp. Cold rotaries don't like to idle.

500 rpm on idle is slow but not that difficult to achieve with a well-tuned carb. Factory spec is 700-750 IIRC. simple enough to increase idle speed through the idle adjustment screw, though if it's running smooth and cleanly at 500, there's no huge reason to change it, unless your plugs are fouling rapidly from being rich at idle or you're stalling out when starting to give it gas.

Rear wheel bearings are a bit of a disassembly job (you have to remove the rear axle, which requires disassembling the brakes & back plate), and actually swapping the bearing itself is best done by a machine shop since it requires a long-throat hydraulic press to do it right.

If all you have is vibration at speed, I'd recommend getting the tire balance checked first, and also make sure you don't have a brake that's dragging due to e-brake cable misadjustment.

A ticking noise that varies with vehicle speed is 99 times out of 100 caused by a rock caught in the tire tread.


Congrats on your new ride.

 

That makes sense, the guy I bought it from said something was wrong with the thermostat, a buzzer will scream until I start driving and it says low coolant but it's at the right level, then once the engine warms it goes off. And I will take the tires to get balanced, that might be the problem, I never thought of that. Thank you so much!

 

Make sure to check the "U" joints in the drive shaft are OK before you get too deep into the wheel bearings.

 

wheels balanced? dont forget the basics

 

um if the low coolant light is on, it might because its low on coolant. also since it idles @500rpm instead of 750 like its supposed too, i'm going out on a limb to link both of those together and say you have a bad intake gasket.

 

god forbid the system works like its supposed to. there was a guy on 8club who thought he a broken tire pressure sensor cuz the light was on. only to find a day later one tire was at 22psi.

be sure you checked the level in the radiator. dont want to blow your engine cuz you filled up your overflow tank and not the rad. its happened.

 

If you read back you'll see I said the coolant level is fine. The sensor on top of the rad has a broken connection, I just swapped it and it's not showing the low coolant warning anymore.

 

same time post. nice. nevermind then

 

Test the rear struts (shocks, really - - these cars don't have actual struts in the back) too, especially the right-side one.

A weak strut or shock combined with a slightly-off-balance tire sets up a harmonic vibration that is a function of road speed.

The right rear shock tends to die first, due to heat from the nearby exhaust & muffler. Replace in pairs, though.

 

Hmm.. It got brand new shocks last october. Could they be loose or something? I don't see them being bad.

 

Could be (especially up top) but they tend to bang around pretty noticeably when that's going on.

My money's still on tire balance. Or your money, I guess. )

 

So I tool it out again and the vibration seems to become a knocking when I slow down. Definitely coming from the back passenger side though. I'm gonna get it on stands tomorrow and check the u-joint

 

If the noise changes between accel and decel, then the u-joint is a likely candidate.

 

I jacked up this car and this is what I found, that clanky noise doesn't sound right... It sounds loose in the differential.

http://www.youtube.com/watch?v=ENmCd3vtBC4

 

Did you grab the driveshaft and make sure the u-joint is not loose? There should be no up, down, or side to side movement. You description sounds like a typical u-joint vibration and clunk. If there is no looseness in the u-joint you might check the rear diff fluid for excessive metal. That would give you a clue about the state of the gears.

 

Try the same test but with the car in gear, so you can see if there's play in the U-joint. Then lock the e-brake, take the car out of gear, and try rotating the driveshaft by hand.

Make sure there's adequate lube in the diff, too.

 

I pulled the shock off the rear passenger side and I think it's bent. Could that cause the same vibration?