Just purchased a 85 FB GSL-SE. Car is unmolested with 83K miles on the odometer; still contains all vacuum lines, cats, etc. Vehicle starts and revs fine first 2 - 5 mins (at 80 - 92 degree Fahrenheit) and pulls strong. No smoke, hesitation, etc....perfect. Within 5 mins after driving (and warmup), car appears to go in a rev-limiter mode; i.e. will not go past 2800 - 3000 rpms. So far, I have only checked for obvious vacuum leaks, spark plugs, rotor caps, cables (all more on a visual aspect). I have also replaced the fuel filter, to include the little mess filter going into the factory fuel pump. I've googled several threats on possible "limp" mode, secondary not opening, TPS settings, etc; but have yet to see anyone say how they *fixed it*. Possible clogged fuel filter made sense and the gent I purchased it from (74 years old) mentioned he had never replaced it in the 30 years he owned it...so I thought it was a good start. I would appreciated some educated suggestions with detailed instructions; but am looking for a 'my car had the same problem, I fixed it. It was__________'. Thanks and have a great labor day weekend 2018. Rock on.

 

ok so there are basically three causes for lack of power, in your case you're looking for something pretty large/basic

1. not enough fuel, i think if you've done filters, you're in good shape here.

2. not enough air. i think step one here is to look at the air filter, and then if that is ok, maybe pull the o2 sensor and see if suddenly it gets better. if yes, exhaust is clogged, if no, its not, move on

3. not enough spark. i would put a timing light on each plug, and if they all fire, you're in good shape. maybe check the coil voltage, it should be around 13v (charging voltage is like 13.6, you'd expect to loose a bit). once its up and running the wires/plugs/plug wires need to be checked or replaced.

1,1. toss up between the fuel pump not delivering enough fuel, and there being something wrong on the injection side. i would test the fuel pump per the FSM.