I did a compression test on my Miata. All 4 cylinders were equal, but about 30 PSI above spec (I assume probably carbon buildup on the pistons).
After I put all the plugs back in it wouldn’t start. It will crank just a couple times, then dies.
BUT : If I stomp repeatedly and quickly on the gas pedal it will sputter and run, kinda. About 1 rev per stomp. It builds oil pressure and the temperature goes up. But as soon as I stop stomping, it dies.
If I just hold the gas pedal down, it dies. I have to keep stomping.
FYI: it’s OBD 1 , so scan tool isn’t gonna help
Clues :
- Its an old piece of junk that has been off the highway for 8 years
- before the compression test, it was running OK, more or less, but with a lot of blow by
- It has fresh gas
- The Cat is not plugged (I took it off to check it)
- It has a new fuel pump and fuel filter
If the only thing you did was to remove the plugs and put them back in,
and it ran OK before but doesn't now, I'd suspect it's a spark issue.
Let's talk this through.
What's the firing order?
Is it possible you have a bad plug wire that's now arcing out on something?
Have you pulled each plug and checked to see if each is sparking when you crank the engine?
Are cables connected to the right plugs?
I had the same thought. But yeah, I went back and checked and they are correct.
Then the engine somehow does not get the fuel or correct mixture of air and fuel. Are the throttle and gas pedal connected via cable? If yes, do the cable and the throttle function as they should?
Does fuel pump work as it should?
Update:
So the (partial) answer is low fuel pressure. I did a fuel pressure test and it was about half of spec.
When I bought it, it had been sitting 7 years with bad gas. It looked like tomato soup. I drained the tank and and scraped out all the rust crystals, but the bottom of the tank still had a lot of rust.
All together I replaced the fuel pump, fuel filter, injectors, and pressure regulator. Didn’t fix it. My only thought was to take the entire fuel system out and start over, including a new tank and sending unit (my best guess is a pinhole leak in the sending unit). But I was looking at about $500 in parts and probably a month of weekends to do it (getting to a Miata fuel tank is a real expedition), and even if it worked, I still have suspicions that the engine is bad (considering it has 170,000 miles and a ton of blow by).
So I called it. A Miata is not my dream car. I got it for cheap in order to learn from, and I did. In the year I had it, I got it running for the first time in 7 years. I did the timing belt and water pump, installed a new convertible top, new seat upholstery, new axles and wheel bearings, new brake rotors, new ball joints, new tie rod ends, and scraped off half an acre of mold and surface rust.
FWIW, when I listed it on FB marketplace, the response was instant. Within 45 minutes, I had cash in my pocket. Obviously people want them.