1977 280z Low RPM and Stall-Out at Operating Temperature

[dasmoover]

Hello guys,

I've got my stock 280z running- for a bit.

I bought the car in this condition.

1977 OEM Stock everything 35k miles.

Car runs extremely smooth when turning her on while cold. Car will run for a good 15-20 mins idling without driver intervention.

Randomly the relay above the EFI clicks repeatedly - as this happens the RPMs drop from ~900 down to about ~500 and sometimes stalls out

if the clicking does not stop. As soon as the clicking stops the RPMs shoot right back up to ~900. After it gets close to operating temperature

there is more chance of hesitation or backfiring when trying to give it gas, other times when the relay clicks any attempt to give it gas stalls the car instantly.

I have cleaned all the electrical connections thermotime switch and CTS especially.

What direction should I head in? It seems the EFI system works until it gets warm. However, the clicking will happen regardless of temperature making it seem like a loose ground or something.

Thing is it will happen with the car idling no one inside and then correct itself.

Any input would be greatly appreciated!

[Zed Head]

The clicking is from the fuel pump relay. It's probably turning on and off because the switch in the AFM is opening and closing. You might have a vacuum leak or maybe the engine just needs a tuneup. One thing you can do to keep it running while you problem-solve is to turn up the idle speed. It might be a little aggravating to idle at 1100 RPM or so but it will get you by while you troubleshoot.

The "fixing itself" is probably just the air-fuel ratio changing as the fuel pressure drops when the pump turns off. It causes RPM to rise, fuel pump turns on, richness happens, RPM drop, repeat. The mix is extra rich when the engine's cold. leans out when warm. Just a possibility.

The small details add up. Check all of the hoses to the intake manifold.