Cold Start and Idle problems

[akorna]

I have a 1972 Z w/manual, stock distributor, three screw hitachis that I recently purchased. Car has been driven little in past 5 or 6 years. Have had cold start and idle problems:

Cold start - full choke applied, takes 10 to 15 attempts to get it started

Will not idle below 1200 rpm, and I need to pull the choke slightly, otherwise when returning to idle (like when coming to a stop) the engine dies. It will restart immediately and sometimes idle, but will die again at the next stop.

Off idle and driving - the car seems OK

replaced:

Battery (would not hold a charge)

Points (heavily pitted)

Distr Cap

condensor

Spark Plug wires

Fuel Filter

Also:

Adjusted valves

checked plugs - looked OK - Autolite 63

I blocked off the air injection system/smog pump and attempted to adjust carbs (speed, mixture, balance). I can temporarily get it to idle about 800 RPM (rough and hunting), but after setting the balance screw and blipping the throttle, it will die when returning to idle. Car will restart immediately, but dies quickly.

Suggestions?

[d240zx2]

Basic questions:

1) How fresh is the fuel and how clean are the lines?

2) Suggest use of NKG plugs. They work VERY well in L engines.

3) Carbs clean? Check out Z-Therapy....

[akorna]

Thanks for replying

1. I've put in about 8 gallons of premium, but did not drain the tank or existing fuel. I guess I could disconnect the fuel line and catch a bunch while cranking the engine - then add more fresh fuel

2. What NGK's do you like?

3. Only carb dissasembly I did was remove the suction piston and check out the needle, clean, put in new damper oil

[lubu]

Sounds to me like you're not getting enough fuel. That's what happened to me when I tried to tune my carbs, choking and coughing and dies... it took me the two days to tune it perfectly. Try to adjust more fuel and see if it idles...I'm thinking your air/fuel ratio arent balanced.

Get a 280zx distributor, it does wonder.

[akorna]

Tonight I was fiddling with the carbs and noticed that the after the choke was released, the jets did not move back up into the carb. The rear carb was the worst. I disconnected the linkage and the jet moves smoothly, but the linkage seems like the springs are not working. Maybe I need to move to the carb forum...

[alhbln]

Have a look at the plugs after the engine dies. If they are bone dry its most probably a fuel issue, if they are a tad wet and smell of fuel you need to have a look at the ignition. The advance mechanism is especially important to look at, as the advance weights could be stuck, fixing the distributor to the initial ignition advance.

With the stock ignition i recommend using NGK BPR6EIX. Those are more expensive than the standard ES plugs but have a finer tip which is much better to get a spark discharge with the (low power) standard ignition. The engine will start more easily when cold or warm and plug fouling is reduced.

[akorna]

OK - I did install the NGK Iridiums and have been doing a lot to the car over the last month - but nothing that solved the issue - still won't idle much below 1000 rpm, and after setting the carb balance and mixture as close as I can, if I rev the engine, and lift off the pedal, the engine stalls or almost stalls. I have 3.5 psi of fuel pressure at the carb and manifild vacuum is a steady 20 in.

I finally spent some time with the distributor - (had already installed new points, rotor, cap, condensor) and verified that the vacuum advance mechanism was working with a vacuum pump. What I did notice, that the breaker plate did not always return smoothly to the base setting. I removed the plate and tried to clean and lube, but it was still stiff and inconsistent. The owners records showed that the dizzy was replaced in 1990. I ordered another one at the local Auto Zone. ($55) - would have been in today except for a freak snow storm in Virginia Beach!

[akorna]

:ermm:I was checking some resistance and voltage readings as I continue to troubleshoot while waiting on the replacement dizzy - attached a sketch of the test - why would I be getting such low output voltage from the coil - is the coil bad?

[akorna]

All,

The Autozone distributor arrived - it was complete with vacuum advance, Points and Condensor. For $55 (after returning the core - $40) seems like a good deal. The points were even gapped!. I did have one problem with it - the plastic insert were the point wire connects to the coil feed wire was too tall and it prevented the distributor cap from fitting properly. I removed it and filed it down - not a big deal.

The car ran significantly better once I installed it. It no longer dies after blipping the throttle. It will now idle under 1000 rpm. The problem was in fact the BREAKER PLATE on the old distributor. Even though the vacuum advance would operate on the old distributer, the plate was binding and catching. Instead of beginning to advance at 3-4 in" hg, it did not begin until about 10-12 inches, and then it would not react quickly in response to vacuum changes.

Next on the agenda is to fix the sticking choke on the rear carb - then some road time and more fresh gas before I do more trouble shooting - hopefully the clutch slave cylinder will be in today.

[alhbln]

Very good! You might want to get hold of a strobe gun to make sure the static advance is set correctly with the new distributor if you havent done so already.

[akorna]

Thanks - I had a dwell tach and timing light connected when I fired up. It was over-advanced, so I brought it back to about 10 degrees - may already have a little centrifugal advance, so it's likely around 7-8. The dwell was a little low at 30 degrees, so I may reduce the point gap slightly to increase.

[jwgarvey]

:ermm:I was checking some resistance and voltage readings as I continue to troubleshoot while waiting on the replacement dizzy - attached a sketch of the test - why would I be getting such low output voltage from the coil - is the coil bad?

Akorna

I may be wrong but I believe the readings on your secondary windings is not at spec, at least not on a stock coil. I believe the resistance is suppose to be higher. Check the FSM. I dont know how that would effect the coil output though. good luck.

John