Zombiez

Found a 1991 300zx coupe NA setting in a barn an brought her home, Bit of a mess they had started the timing and never completed it. So I redid the timing, replaced the injectors, cam angle sensor, fuel pressure regulator. Replaced all the cracked vacuum lines and she fired right up. Drove it around the neighborhood couple days just taking it easy on her and everything seemed great. Took her out on the main road and got her up to 60 mph and all good until she warned up. Then she started bucking very hard any time I tried to maintain a steady RPM over 2500rpm. If I get into the throttle she stops until I let off. Any ideas on what's going on?

DragonSlayer

Run the ECU codes for a place to start.could be a number of things

Zombiez

Found a write up on how to and got 43 and 13, so throttle position will be a pretty easy swap, but engine coolant temp, guessing there is two of these since the gauge on the dash works.

DragonSlayer

The TPS will really screw with the performance of the engine. Google how to check it to see if it is set correctly . I would go ahead and replace it. Usually cleaning the contacts on the coolant temp sensor and harness connection will straighten it out. Facing the engine it is the one on the left with the 2 wire connection and it will probably crack when you mess with it so be ready. You can get a replacement connector and splice it in .

Zombiez

Replaced the TPS, cleaned the temp sensor connector "and every other connection I could see, cleaned the throttle bodies and ran a can of Seafoam through the intake lol smoked so bad you couldn't even see the neighbors house across the street, but she runs and idles slot better now and no more surging.

Here a small vacuum leak somewhere so going to get some brake clean and go hunting. And almost doing like a solenoid buzzing every once in a white somewhere on the back of the engine. Are the NGK "2300" pfr6b-11 pretty much the gospel plug to use on the NA?

DragonSlayer

Those are the plugs I use, they were supposedly designed for that engine. The easiest solution for the vacuum leak is buy the silicone replacement kit and just start replacing them one by one. On an older car it is going to be a necessity anyway.

And by the way, welcome to the world of Z lunatics

Zombiez

Lol thanks I had a 240z that I did a lt1 swap in years ago for track fun, but had to move a couple times and didn't have a place to store her so ended up selling. Now I have room and some time and a new toy lol.