So I'm importing this 280ZX I picked up from Florida a few months ago. She sat in a garage for the last 13 years and wasn't running so when I got it I...

Replaced the fouled gas tank/sender, fuel lines, injectors, and fuel filter. Replaced the rear brake hose and rear calipers and brake pads (old ones soaked with brake fluid). Resurfaced exhaust manifold and replaced broken bolts with studs on exhaust. Replaced broken wheel stud. Replaced square tires with the one's off my Jade Gray 280ZX (since she's running on Rota RB-Rs now ) Fixed brake light switch/bumper. Replaced struts with the last set of Tokicos left on the planet (not quite but a pain to find now adays..) and new boots, TC rod bushings - that seems to be a given on any 280ZX and a steering boot for the tie rods and a new outer tie rod.
. New Castrol LMA brake fluid, Redline MT90 in the tranny and Shock Proof in the diff, Penzoil Platinum 5W30 and a Purolator filter. Probably missed some stuff - been working on it for months to get it ready for inspection - way more work than I was counting on for such a pristine car lol.

So anyhow the issue I'm having (other than the head lights/wipers but that's the last thing on the list and she's ready for the inspection) is a weird shake at about 1700 RPM. Seems to be independant of everything other than the RPM itself. Get above or below that and it seems to smooth out. Idle is good as well. I haven't been able to find any problems like this searching for "shake". My buddy is a mechanic and he's scratching his head. I've seen weird shakes at idle with injectors not firing, etc but this seems different happening around 1700RPM makes me think something is out of balance but no idea what it could be - ideas?

 

Timing (advance?) ?
AFM carbon track?
Read the plugs?
Cap & rotor?
Spark plug wire grounding out?
Intake manifold leak?

Hook up an a/f gauge.

Those are my ideas.

 

As usual I missed some details - already did new plugs, wires, cap and rotor (set the timing) - probably not a manifold leak since we replaced the gasket when we resurfaced the exhaust manifold but that's worth checking. AFM sounds like a good candidate...

 

AFM if you staying still!!

Engine mounts/tranny mount or diiff mount if you are driving???

 

Harmonic balancer.

 

I had s130 come to me with the flywheel loose. That one was a surprise. I was gonna say motor or trans mounts like borini said. Is this a free rev vibration or driving vibration? What does it do under load at that rpm while driving? Does gear selection matter or neutral? So many questions. Loose dizzy shaft? Just shooting out some odd ***** here to get the ideas flowing.

 

Yeah I replaced the AFM but there is an issue with #6 injector firing so it's time to replace the connectors. Anyone know where I can get a set (hahah )

 

when i go thru emissions testing i actually unplug #5 injector to use up my extra fuel and create a bit of an air pump. weird part is the car doesn't run too bad, has a miss but only to about 2000rpm, then it smooths right out. if yours is only at 1700 it must be a harmonics problem not so much an injector. maybe ignition but thats more unlikely with all the replacement that you have done

 

I'm betting there's a bare spot on the AFM carbon track at the 1700 rpm point.

Check out J's AFM rebuild instructions here:

http://www.kamikazeracing.org/dl/JsAFMRebuild/

 

Already put in a rebuilt AFM