1990 Mazda rx7 motor in need of help

I have a 1990 RX-7 I bought it and I test drove it everything went good. So I bought it. I drove 20 miles to get gas and it smoked like crazy on startup. So I called the people back and they refused to take the car back. I'm kind of stuck on what to do about it any help would be great on what I should do.
Also if I am stuck with this car I was thinking to rebuild the motor or replace it. What should I put in it? JDM 13b t or would a 13rew be out of the question since every mount is different and would it fit. What would this cost for both engines if it is a stock 13bt i would replace it myself because i am in an automotive program at Wyotech and can use these facilities. Any advice is welcomed.

I have a 1990 RX-7 I bought it and I test drove it everything went good. So I bought it. I drove 20 miles to get gas and it smoked like crazy on startup. So I called the people back and they refused to take the car back. I'm kind of stuck on what to do about it any help would be great on what I should do.
Also if I am stuck with this car I was thinking to rebuild the motor or replace it. What should I put in it? JDM 13b t or would a 13rew be out of the question since every mount is different and would it fit. What would this cost for both engines if it is a stock 13bt i would replace it myself because i am in an automotive program at Wyotech and can use these facilities. Any advice is welcomed.

Throw a renesis in there!

I also can't spend the 7 grand to put a renisis in there.

also I am having problems starting it. When it starts it turns over very hard and shoots white smoke out the tail end then smokes until it is warmed up.

a renesis doesnt cost 7k and if it did then throw a 20b in there and have fun you can get a 20b for 3-4k. Reason why I suggested the renesis is cause since it's new it is very reliable. you could see around different wesites like e-bay to see if they might have one for a good price.

The smoke could just be condensation from the initial warm up. I thought my engine was a goner, then a noticed water dripping out of my exhaust.. my exhaust is fairly large so there's more surface area for water to catch on to the cold exhaust. The "smoke" never really happened to me, until it started getting cold out. Do you start the car regularly? Did the previous owners have it sit for a long time before they sold it to you?

Well it isn't condensation in the exhaust because when it starts it turns over hard and takes a couple seconds to start. It shoots white smoke for like 3-4 minutes. after it is warm it runs like a champ. but until then it is really rough. Also when you rev it to 2-7 grand it revs up then bounces up and down like you are featehring it.

normally throwing white smoke out is coolant, but if it's just starting it may be something wrong with your cats. they are known to clog up the exhaust system when they get old and cause issues.

and in my experience, most rotaries take a few seconds to start

Serious issues? ..because I've been looking for a good reason to get a mid pipe haha.

I had that same problem with the white smoke....and the bouncing rpms during start up....my car had 90,000 miles so it wasn't to bad but I changed my o2 and it stopped the white smoke for me. but the bouncing rpms still happens until warm up.

oh yea check ur dtc's. good luck man.

The 7 has no cats. Could it be the o2 sensor?

The revin 7 does not have any cats in it. I took it to a mazda dealership just to get an opinion. They said they think it is the fuel injector flooding the engine on sartup because aftrerwards it runs great. So I am going to check that out to see if they are dirty. I am going to compression test it this week sometime. What are the numbers? I heard around 95 pounds is good. Also the it starts up it will take maybe 5-6 seconds to come to life after a hard start. Could this be from the previous owners letting it sit to long and the apex seals rusting to the housing then when it is turned over it tears some housing wall off losing compression?

yeah, throw some atf or mmo in there thru the spark plugs and turn it by hand a little (you might want to replace your spark plugs afterwards)

What would be the point of putting some ATF or MMO??? into the motor?

lubricate seals and give a better surface for compression. if the car's been sitting that's what you should try to do.

what is MMO? and how much wold i put in a mL or so?

Marvel Mystery Oil = MMO.

I guess put in a much as feels right, sorry for not being specific, but once you see it you'll get it. There's only so much you can pour anyway.