New to me 76 280z with problems

[skunkteeth]

Hello everyone, I just got my 76 280z and I am having a couple of problems. It is a L28 with 5 speed, ac, and electric ignition. The valves were recently adjusted and the injectors are new. The AFM has also been recently rebuilt and I just checked it and everything looks good.

The first problem is the gas mileage. I am only getting about 16 MPG driving very easily. It smells like it is running rich and there is soot on the bumper near the tail pipe. I have checked most of the connections but I still need to clean the water temperature sensor. Should I remove the thermostat?

The second problem is the idle speed. In the morning when it is a little cold (southern california cold...) the idle speed is about 600-700 RPM's and is pretty rough. After I get to work and it is warmed up the idle is about 1200-1300 RPM's. I am guessing this is because of non metered air getting into the system. I checked the EGR and it is not sticking. The hose between the AFM and intake looks good, but I noticed a little metal loop inside, is this from when it is molded? I tried adjust the idle tonight. I tapped the gas and it shot from a rough 600-700 to 1200. I tried adjusting it down and it wouldnt move much. I looked over the vacuum lines and didnt see any cracks.

Third, when going at highway speeds the voltage gauge will bounce up to 16 and down to 12 when it is usually a stable 14. Do I need a new alternator?

I have the EFI bible and FSM, I am going to start the troubleshooting it lists tomorrow. It says to check the throttle plate and BCCD valve. Any tips on removing these? This is my daily driver so most large work occurs on weekends.

Thanks, any help is appreciated.

[mgood]

Kyle, good to see another 76 - 280z to join. I don't have any answers your questions but I am also interested in the mileage. I am also getting around 15 mpg. My car has always been low in gas mileage from day one and I am the original owner.

[skunkteeth]

Interesting mileage mgood, I always thought these cars got around 20-25.

An update on the idle:

This morning when I started the car, it was at about 600 RPM idle running rough, the gauge was bouncing up and down. I tried to adjust the idle speed up but nothing happened. After I actually pushed down on the throttle rod in the engine compartment the idle seemed to shoot back up to 1200 RPM, and thats where it stayed even when I was at work. Any ideas?

[Sailor Bob]

I'm suprised to see so poor milage with the five speed - I have a four speed and I'm figuring 15-20, depending on how I drive . Even concidering the difference in the gallon, I am getting the same or better

Idle speed is certainly a factor 1200 is way too high - I think 700-800 is about right, check your manual or try a search.

I get the mess on my bumper as well - if you find a cure let me know.

[KDMatt]

Hrm, okay let's see.

Is it possible that maybe you have some junk in your fuel lines?

I imagine it's possible that maybe you're getting spotty fuel flow, causing low rpm's, then maybe when you give it some gas you clear some junk out of the way causing a stable idle?

Otherwise you could examine your auxiliary air regulator, I think part of its job is to raise the idle speed a bit when the engine is cold.

If it regulates in too much/too little air it could cause wacky idling.

Those are just my stabs in the dark, sorry I can't be of more help. Welcome to the club, '76 and '75 seem like underrepresented years for the Z.

Since you just got the car, it might not hurt to run a can of seafoam through there either.

Mgood: Your VIN is only 5000 off of mine it looks like (Mine = 286119)

[skunkteeth]

Well the engine has been recently rebuilt and the PO said that the fuel lines are all new (which they look new) and the fuel tank was cleaned out. Alot of it has been worked on, it just has a couple little things to be done. I will check the AAR tomorrow.

Thanks

[Cethern]

My 75 would have some odd idle issues at times and I never found the problem but it didn't happen a lot so I never paid much attention to it...Now my 76 is a different deal I thought I had found the problem and had it fixed so for a couple of days it ran great now it's back to being a pain..

For your deal and mine I would start with a vacuume gauge and see where it's at. Then clean all the connections,check the grounds. Then just as you stated get the EFI and FSM books out and start testing.

Eric