So you changed the fuel pump on a hunch rather than measuring the fuel pressure?
And you have trouble getting the engine warmed up because it stalls?
Do you have a CEL on? If so get the codes read. But don't let anyone talk you into replacing sensors without trying a few other things first.
That feeling of the engine running out of gas could have other than fuel related causes.
Does the exhaust smell of unburned fuel? Is the exhaust tip all black and sooty? It may get to much fuel by way of a bad fuel pressure regulator.
Here are the things that I would check:
1. Vacuum leaks: any leaks on the intake side could lead to lean conditions and if bad enough stalling. The air intake hose is prone to cracking. Any old vacuum lines could be cracked or blocked. You may just go ahead and buy 15ft of it to replace them all. Check the brake boost hose and the PCV hoses as well. The lower intake manifold gasket may leak. Use a length of garden hose, one end to your ear the other end around the idling engine to listen for the tell-tale hiss.
2. Clean the MAF sensor.
3. Clean the throttle body.
4. Clean the EGR ports
5. Check the EGR boost sensor hose and the nipple at the intake manifold for obstruction using a stiff wire.
6. Check sensors using a multimeter. Use the Haynes manual or online resources to get the specifications and the specifics of the procedures. This includes the ECT (engine coolant temperature sensor) AIT (air intake temperature sensor), TP (throttle position sensor), EGR boost sensor and MAF sensor. There are more sensors, but the ones I listed are key.
7. IAC valve (idle air control valve.
8. EGR valve: clean it out and reuse it.
As a general rule: checking, cleaning and reusing saves bundles of $$$$.
By the way, I don't have a Miata, but you do that kind of thing around any engine.
Good luck to you!
Last edited by tanprotege; 10-02-2011 at 10:52 AM.