running rich

[Bob Marcho]

I just installed my rebuilt engine in my 1986 300ZX and took it out to the local dragstrip to check everything out. First run was great, but on the return road I could not keep the engine running below about 2500 rpm. I staged again, but had to keep it running above 2500. Ran it through a 2nd time; it stumbled pretty bad off the line, and then she ran great after I got it up in the rpms.

Brought it home, started it up to unload off the trailer and everything ran fine. Drove it slowly aroudn the block and as soon as it warmed up and the thermostat opened up I smelled gas. I looked out the rear window and black smoke is puffing out, it wouldn't run below 2500, which appears to me to signal running really rich.

I can rev it up and it runs great, but again it will barely idle until it goes above 2500 - 3000 rpm.

Any suggestions where to look?

Thanks,

Bob Marcho

[x-ring]

Originally posted by Bob Marcho@Oct 29 2005, 10:27 AM
as soon as it warmed up and the thermostat opened up I smelled gas

[snapback]63971[/snapback]

Not much experience with the later Z's, but the first thing I'd look at would be the thermotime switch/circuit, assuming your year has one.

[Joe Harlan]

Originally posted by x-ring@Oct 31 2005, 06:12 AM
Not much experience with the later Z's, but the first thing I'd look at would be the thermotime switch/circuit, assuming your year has one.

[snapback]64079[/snapback]

Coolant sensor signal is bad. ( BAD SENSOR OR BROKEN WIRE)

Joe

[tac911t]

Originally posted by Joe Harlan@Nov 2 2005, 07:29 PM
Coolant sensor signal is bad. ( BAD SENSOR OR BROKEN WIRE)

Joe

[snapback]64398[/snapback]

I agree. The sensor tells the fuel system when to cut out the cold start circuit (rich circuit). Your car runs fine when cold or at WOT, but once the car warms up the circuit is not decreasing the fuel for a warm running engine.

Todd