RoadWarrior Reader
5/20/13 1:45 p.m.

So, my loud, lowered, race-seated '94 miata mostly survived it's ~ 3500mile trip from Boston to California. But now it seems to be having some issues with hard starting and lack of power. I noticed it a little bit when I hit altitude crossing the rockies, and thought I chalk it up to that. But it seems to still be there in some shape.

So before I left I gave it basic tuneup, fresh oil change, new fuel filter, regapped the plugs, new plug wires, new denso o2 sensor, new ecu coolant temp sensor, etc etc..the poor car is progressively having a harder time starting (especially in the morning or sitting after a long period of time)and a definite lack of power at the higher rpm ranges. Checked the plugs, they look decent, and the gap is about right, air filter isn't clogged, and no CEL's are stored in the ecu. Tried different grades of fuel and it makes 0 change.

Soo...I'm not sure where to start on this one,I only have a few of my tools unpacked, so trying to figure out the easier ones to check before I start tearing into it. Any good idea to test the pump sans a fuel testing gauge? If not , I might need to find a local harbor freight and make that happen. Could a failing ignition coil be another possible suspect?

What are your thoughts?

mistanfo SuperDork
5/20/13 3:29 p.m.

My experience with Miata fuel pumps is that they either work, or they don't. No real in between (not saying that it can't happen). Coil is possible, know anyone with a similar model that you could do a quick swap to see if it solves the issue?

amg_rx7 Dork
5/20/13 7:52 p.m.

2 ways I know how to check for a weak fuel pump. 1. monitor fuel pressure. As the pump wears, it is not able to pump at higher pressures and fuel pressure decreases as revs / fuel deliver rises. 2. check spark plugs to see if they look like they are running lean.

Before doing that, I'd check voltage on the alternator.

what year miata?