Problem: Engine runs flat and has no top end, 50-55 MPH seems to be the max speed. (Chronic problem with the Samurai…)
1. Carburetor vent fix. See the tech service bulletin
2. Check the grounds from the firewall to the battery negative post and the distributor, either of these being bad will cause a ground loop that the computer can’t deal with.
3. What gas are you running? I’m having the best luck with U76 gasohol. You can start by putting in some alcohol based gas line antifreeze. Also check your compression. Low compression does not help for making HP. (I see 1.3’s at 140 all the time, and 170 is the lower limit for wear per the FSM. 195 is stock…)
4. Is the coil stock? If so, they are notorious for going half-bad. Bad enough to do what yours is doing, but not bad enough to die. I believe it is because they are fed 12 V full time and were designed for the old 8V you got from dropping resistors in disty’s with points.
5. Timing belt slipped, off 1 or more teeth.
6. Cam to crank timing out of spec. Has the block been decked or the head shaved?
7. Check to see if the catalytic converter is clogged.
8. How I finally killed my gremlin!
It was in effect, a vacuum leak. The ABCV (Air Bleed Control valve) was leaking on one of its 2 ports. I would have assumed a diaphragm inside, but the FSM shows it as some sort of ECU controlled needle valve. I had another I got with an intake assy I had bought just for these sort of spare parts, and bingo! It perked right up! idles stable as a table, and the Digital VOM on the O2 sensor shows what it’s supposed to show!
I took it for a test drive down the freeway and while it’s no dragster, (it is a zuk…) it has no problem getting to 65, maintaining it at less than 1/2 throttle and even accelerating on past 70 (75+ at one point) with minimal difficulty