1997 red 5 spd Miata running fine with plenty of power before I changed the timing belt.
Still running fine, but within 100 miles of timing belt work, Check Engine Light came on. Scanner at first place I took it to showed idle circuit problem. Tech spotted loose clamp on intake end of snorkel. He reset the computer and tightened clamp.
Car running fine when red light came on again about 50 miles later, but not running well at all after intake manifold cleaned out. Now it runs terrible but only at certain speeds and loads as described below, but CEL does not come on. We drive it when we think we can stand it.
Had it to the Mazda dealer in Brandon last month. Tech drove it and found that, yes, it did feel as though someone were turning the key off and on when driving 30 mph in 3rd gear. Also problems in 4th at around 42 mph, 2nd at around 14 mph, but 30 in 3rd is the worst. Seems to be related to grade of road too. If it is pulling up a central Florida "hill," it is more likely to run steadily.
Like the folks at Dossey, tech at Brandon Mazda dealership also suggested just driving it, hoping that the red light will come on so that computer can provide a clue as to what is wrong.
I have to say that I was surprised. I expected the dealer to be able to hook it up to some sort of scanning equipment, see what was going at various speeds and various load conditions (30 mph in 3rd in particular), then diagnose and fix the problem. Nope, not able to do that. Just drive it until the check engine light comes on.
Folks at Firestone, where I buy most of my tires, suggested that cleaning solution used to clean intake manifold might have damaged a sensor in the intake.
Is there a sensor in the intake that could be causing all my problems?