mobcharge

Hi everyone. Just got a 1979 280zx the other day.
Got it for my wife, since i am into muscle cars but wanted her to have a fun car too.

It has 95.000miles on it, has been well maintained (came with a big bunch of documents and receipts). Anyhow, as you all know, it is quite easy to fall
in love with these cars and i did, right away, so i have been driving it around town everyday with a smile on my face.
Being use to GM and FORD big block cars the performance of the stock
engine with all the CA emission stuff on leave some to be desired performance wise but.. Cant beat the comfort and fuel economy, makes my old corvette feel like
a relic from the stoneage (well it almost was.. but still..).
i like it, guess i would like to hotrod it later. But first i want to get it to run as good as i can stock..

Anyhow.. my question is this, it runs ok, might be a little tired but...
when idling it sits around 850rpm only to drop to 800 for a tenth of a second and then jump back to 850, it does it maybe every 3-5 seconds but irregularly.
Same thing if i hold it at say 2000rpm, it drops maybe 50-100 rpm and then jumps up again.
And again same think if driving down the road at a steady rpm.
Ideas? I do realize i have a lot to learn since the engine bay is filled with a lot of stuff i am not use to have to deal with. Thinking about spraying some carb cleaner everywhere to look for a small vacuum leak but wanted to ask here since people obviously know what they are talking about.
Anything that would steer me in the right direction would be GREATLY appreciated.

Will post pics of the car as soon as i get my camera working

PredatorZ

Here's a link to the factory service manual in PDF form you can download for free.http://www.xenons30.com/reference.html
With older Z's electrical problems can become a real big issue, after 30 years you get corrosion in some of the main connectors, also the ground can be suspect and cause your car to act weird. Here is a recent thread that has some of Fricfrac's electrical genius included. Follow his recommendations you cant go wrong https://www.zdriver.com/forums/280zx...500-rpm-36014/

rogerz

here is a start on some things that probably need doing and will make the car more reliable. the s130 is fairly bulletproof and primitive enough that you don't need an EE degree to understand it.
Get your battery load tested. Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen.

Clean the connectors for the maf, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion.

Replace outer tie rod ends, and ball joints. replace the bushings with poly (don't forget to lube them as directed unless you like squeaky things). New shocks. all those things will make you think you are driving a different car. doing them piece meal is a waste you won't see a great improvement until you do the complete job. Rear bushings nice too but more work and you won't notice as great an improvement. Rear shocks also because if the fronts are gone so are the rears. if car squats when you jump on the gas the rears are gone. If you have the electro adjustable shocks they are DEFINITELY GONE.

use an unlit propane torch to spray gas around the engine if it starts to run hotter probably a vac leak. Quick and dirty test pull the oil filler cap while hot and idling. If it continues to idle unchanged you probably have a vac leak. if it runs worse then that is good. check the fuel pressure. check all vac hoses they are usualy rotten by now.

mobcharge

Thanks for the pointers, it is greatly appreciated!

Ok, heading over to the garage to see what can be done. thanks for the pdf link, will check it tonight.
Feels like the first time i worked on a car "what is this, and what on the earth is this, and this.." hehe

About the suspension, the old owner spent a lot of money at a Nissan shop to do front and rear suspension, brakes as well as ac etc less then 2 years ago.
About 3 times more than i paid for the car, might be why i am love to drive it too

mobcharge

Ok, finally had time to go trough everything and now it runs like a charm

Well except for one thing, it wont downshift when i floor it. Where do i begin to look for a solution to that?

Any help would be greatly appreciated!