1992 miata hesitation under 4200rpm

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1992 miata hesitation under 4200rpm

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1992 miata hesitation under 4200rpm - 2/8/2008 7:54:13 AM

oneshot onekill

Posts: 17
Joined: 2/8/2008
Status: offline

I just bought a used '92 Miata with 170,000 miles as a project. It's a 5 speed. The motor seems to run very nice. No tapping or rattling, smooth acceleration in neutral. Sounds great. Here's the problem: When I'm accelerating through the gears the car seems to hesitate and and surge until I reach 4200rpm and then it pulls like a horse. During acceleration the engine sounds like it's firing properly and the rpm's increase evenly but the ride is jerky and uneven. I changed the spark-plugs and wires. I replaced the fuel filter. I've run a tank of injector cleaner and I even sprayed the crap out of the throttle-body with throttle-body cleaner (but did not remove it, just sprayed the paddle and down its throat). I've read a bunch of opinions on similar problems but most either don't hold water or I already tried them. I don't think it's a weak fuel pump or it would get worse at higher rpm's... right? The O2 sensor has been suggested but I believe I would have a "trouble" light letting me know... right? The clutch is a little high but it seems to grab like it should. Anyone know what my problem is??? Besides not being smart enough to figure this out?! Thanks in advance!