Rattle and no power on the pedal

What is wrong with this car? There is no check engine light, but when I try to accelerate, especially going up a hill, past 2k, there is resistance and it feels like I have my foot on the brake, and gas pedal at the same time. The car will not go past 40mph going uphill. I have had the spark plugs changed, still no good, I have emptied the gas, in case it was bad gas, I have added water cleaner to the gas tank in case it had water in it, was worse, added sea foam to clean the engine, then 40k to clean the gas tank better, seemed a bit better, now worse, added cleaner to the gas tank for my other things, forgot the word, and still my car does not accelerate, and rattles. I have had a car guy drive it, and I had a mechanic hook it up to a computer, some reading d4, said intermittent missing, I could tell them that! The words possible coil, cam, electrical , have come up, but the guy who drove it, didn’t think it was the cam or coil?? any more ideas before I start spending lots of money to this guessing game, before someone comes plowing into me? I just bought this car with 100,000 miles to own a simple car that works, after enjoying my jaguar for 10 years. If I didn’t need a car for work I would toss them all away! This is a Mazda miata

There are a lot of things that can cause this. It will be impossible to diagnose without more information. Can you get the codes read and post them? At first glance I would possibly look for an exhaust restriction such as a plugged catalytic convertor or a plugged fuel filter.

The first things to check for a problem like this are, in no particular order,

  • fuel pressure
  • exhaust for any restrictions (may as well check the intake tract too)
  • engine compression
  • “feels like I have my foot on the brake, and gas pedal at the same time” - and dragging brakes

But seriously - we don’t even know what year this car is, how many miles are on it, what kind of maintenance shape its in (other than fresh plugs and a clean gas tank), or…

…what kind of transmission is in it.

@oblivion is correct. It sure sounds like a clogged cat!

I had a rattle, too, and then lost power. So I checked the oil, and there was no oil on the dipstick. Timing chain had slipped. 2003 Mazda 6 with 58,000 miles. Only 4000 miles since last oil change.