76 280z with some 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.

 

 

(I copied this from my post on classiczcars, I am just trying to get as much help as possible:-|)

[COZY Z COLE]

Add this to your reading/troubleshooting list...http://www.atlanticz.ca/zclub/techtips/EFI&fuel.htm

 

 

 

LARRY

[naviathan]

Gas Mileage and running rich - Sounds like your AFM needs to be adjusted. First lets fix the other problems though as they could make it immpossible to set.

 

Idle Speed - Probably a vacuum leak. Check the brake booster line and around the intake at the head. You can use a can of carb cleaner to spray around things and listen for an idle change.

 

Voltage - You probably just need a new voltage regulator. You can have it checked at just about any auto parts store for free these days.

[SkunkTeeth]

Thanks for the link Larry I have it but forgot to check for a vacuum leak section.

 

 

Thanks naviathan, I will try the carb cleaner idea.

 

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?

[naviathan]

Clean the ball joint connection in the throttle linkage.

[Careless]

Thanks for the link Larry I have it but forgot to check for a vacuum leak section.

 

 

Thanks naviathan, I will try the carb cleaner idea.

 

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?

 

 

Mine has similar problems at times

what i do before checking for possible problems is i pull the pedal back with my foot. all the way up to the highest position.

 

when your idle is crap on a startup, i would adjust the distributor position for timing while warming up, make sure it's at about 1000 rpm.

 

then when it's warm, and you'll know, because at this point, your RPM will be somewhere like 1800... you would adjust the idle speed screw until it's at 800 RPM instead of 1800.

 

The reason (i think) for this is that it seems like your idle pattern is reversed, in that when it's cold it's dying, because there's too much AIR going through the idle adjustment system because it's opened too far wide. and when it's warm, it's at the state where it can idle properly, but again, it has more air now, so it's compensating and making it idle high now. the cold start procedure that the computers run through are supposed to dump excess fuel, through an intake tract injector, or a secondary port no?

 

play with both until it sounds homogenous in its firing pattern while it's warm... then let it cool down, and start it up and make sure it's idling HIGHER when cold then when it's warm, not the other way around... i actually give it a bit more advance at the dizzy just because i feel it will stumble less if it has a hair more advance, therefore on a really cold day, the lumpy idle wont rear its head again.

 

im not sure how your engine is, but on my N42/N42 engine/head this is how it runs best without using a timing light or anything special.

 

now that my injector #4 is either clogged or bunked, I don't do any of this.

[SkunkTeeth]

Thanks careless Ill have to look into the timing also. I think it might be something with my throttle assembly, I have about one inch of slack before the gas pedal has tension, so I though the TPS might be having some problems. How much slack do some of you guys have before the gas pedal has tension?

[Careless]

Thanks careless Ill have to look into the timing also. I think it might be something with my throttle assembly, I have about one inch of slack before the gas pedal has tension, so I though the TPS might be having some problems. How much slack do some of you guys have before the gas pedal has tension?

 

mine has bout 3/4 inch and doesn't spring back fully.