did a complete tune runs good at idle,now right at 2000 rpm's it cuts on and off,you can slow it dowm and it will rev higher but it won;t hold.why does it pulse back and forth ?
emission testfailed,HC was 422 to be 220 loaded,idle was1084 to be 220.CO good on 1990 Toyota Supra
you say at 2K rpms itcuts on and off. Is it like the rev-limiter is kicking in? If so get it scanned by a shop that will be able to read 'live' data and see what the sensors are doing. A wild guess would be a dead spot in the TPS , but that's a wild guess.Put a vacuum guage on it and watch and record the readings and whether it's steady or smooth , and reply with that info if the scanner bit is unavailable.
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Check for vacuum leaks if your idle is surging erratically.