My started as an 87 naturally aspirated RX7. Yadda yadda yadda i blew the motor and put in a turbo motor. I screwed up the swap a little by leaving naturally aspirated driver side wiring harness so i know i have a million electrical problems. Anyways 6 months ago i got the car started. It ran rich and had a rolling idle that would sink and rise depending on the clutch position. I also believe it was getting fuel cut at low rpms. However, the car was still driveable, at least for an around the block test drive. Now 6 months later i go to test drive it again only that now it can barely drive at all. I could get it to move when i slipped the clutch, but most of the time the car had dry heaves. It spastically accelerated and engine braked. Even though the car hasn't been changed in 6 months why would its drive quality decrease dramatically? The only things i can think of is that the gas is now over a year old and 6 months ago i was driving it in the Chicago winter. Other than that i am clueless. Any help will greatly be appreciated.

 

Bad gas? Modern gas is only good for a month or two of sitting.

 

The low throttle cuts you had before sound like the TPS.

Clip a meter on it & check for resistance drop-outs as you work the plunger.

Also maybe clean up the firewall to bell housing ground.

 

If gas is only good for two months then why does my lawnmower run fine with gas that has been sitting for 6 months

 

Because lawnmowers are very, very simple engines with carbs that have wide jets (for the size of the engine). Believe me, I have seen many lawnmowers (I used to repair them full-time in my highschool days) that have sat for more then a few months. Two things can happen:

1. It will run fine

2. The gas will turn into a horrible gell/varnish that will clog everything

Either way, it is NEVER good practice to leave gas for more then about 2 months. After that period, it starts to degrade. If you need to leave it for a while, use a fuel stabilizer.