Miata Fuel Issues

[AutoXChris]

My dad picked up a 1992 Miata with 120k miles or so... I personally drove it around today! Drives great!

Issue is too much fuel on start up and at idle... We found this by trying to start it, crank crank crank. Pull the injector wires so it starves the fuel, crank crank sputter run die.. Plug in the injectors, crank run... No issues other than a rough idle with a rich exhaust smell. Drives great through the rpms.

We have a fuel pressure issue... Too rich on startup and idle...
Maf?
Fuel pressure reg?
Fuel pump?
Faulty sensor?

All this is running through my head...

[budweeks]

Chris,

Leaking injector(s)? Injectors not seating and bleeding down at stop and at idle?

Bud

[96LT4AX]

You see where this is going. Restriction downwind could make it hard to start, but let it run once lit. A potato jammed in the tailpipe is the extreme case. Just a thought, but the 97 I just bought has 68K and a catalyst that needs to be replaced.
Good luck.[/b]

[JimR]

Something may be metering incorrectly, and the ECU is compensating with extra fuel. A lot of modern cars will have a cold/idle run mode, and a warm operation mode. Different settings, different sensors and emissions equipment used based on temperature.

Check all grounds before you replace anything. The ECU probably has a diagnostic mode, too. On my Nissans, you turned a screw, and the ECU would flash the check engine light in something like morse code. The service manual would tell you what codes the ECU was holding. A Miata factory shop manual would probably be really handy.

Since temperature and idle are involved, I'm guessing things like corroded wiring grounds, coolant temp sensor, MAF, throttle position sensor, etc.