260z stalls at idle after warm up. Carbs?

[SteveJ]

What ignition system are you using?

[Rill Cosby]

Rob, chokes open and close fine and do not stick.

Steve, I'm using the stock ignition points system that came with the vehicle.

[240260280z]

Set your timing and jet heights after the car is good and hot. Besure to balance the air and fuel into each carb at idle and at 2,500 rpm.

For cold starting, be sure to use the choke.

Also make sure your TDC mark on the pulley is correct (get cylinder 1 at the top of its compression stroke then check the pulley marks). Some times the pulley separates and the timing marks creep.

[SteveJ]

Keep in mind that the stock 260Z system did NOT have points. It has a transistor ignition system. See the EE section of the FSM starting on page EE-27.

Okay, we may need to move our focus. Verify you're getting a good spark when the car is warmed up. I'm thinking that the stock ignition system may be the issue. Look for an erratic spark with your timing light as the car warms up or any drift in the timing. Check the transistor ignition box in the passenger footwell to see if it's heating up. If so, turn a can of air upside down and spray the box so the liquid hits the box and cools it off rapidly. See if the car restarts easily. Unfortunately Nissan only provided directions to test using a testing box. There is this thread (http://www.classiczcars.com/forums/electrical-s30/49087-datsu-260z-transistor-ignition-system-service-manual.html) that says there is another testing method. You could PM DRBall to see if you can get a copy of it.

Was the car initially an automatic? If so, try unplugging the temperature switch. It's a Yellow/White wire that should be around the thermostat housing.

I've never played with the stock system. A PO installed a ZX distributor/ignition in my 260Z. I think that's what a lot of people have done.

[Rill Cosby]

Air and fuel has been balanced at 2,000 RPMs whenever I did it last. After I bring it down to idle speed I never get a consistent idle. Sometimes I get an idle of 900, sometimes it'll find itself around 750. Seems to depends on how close to death she is.

I've been checking timing with a light every day for the course of this week. Only time the timing changes is whenever I do so.

[Rill Cosby]

Steve, those sound like some very interesting things to check out later on today. I go out there everyday to work on it and find myself pretty much fiddling with the same thing expecting something to change. So anything new is appreciated. That link you posted also lead me to some other information that I could try to narrow out some issues.

I seem to be getting good sparks from the spark plug wires and no erratic light flashes with the timing light, but I only checked #1 spark plug wire with the light for timing issues. I'll check through all of them today.

The car was born and raised a manual. I've read a lot about people changing the ignition system in their Z's and the benefits but I always believed "Don't fix what isn't broke." Except, you know, it might be broke.

[Rill Cosby]

As I was running the car I started checking electrical wires until I ran into a loose connection on the ballast resistor. As I shook the wire the car died out and I got excited thinking this could definitely be an issue. I flipped the resistor over to tighten the connection and with the slightest turn this happened.

So all connections cleaned and tightened on the resistor and still having the same issues. I'm not sure how hot the resistor is supposed to get but I didn't think it would get THAT hot, to the point of burning my finger. Anyways, at least it's nice to fix these little things that can arise in the future.

I did what I could with the transistor ignition box. I took the cap off of the box and after she stalled out again I took air from an air compressor and blew air all over it. I'm sure it wouldn't cool it off as much as using the upside aerosol can so it didn't help with any quicker of a start up. I even tried putting a blower on the box while it was running to see if it would prolong the idle time, which it didn't.

[SteveJ]

Well, that ballast resistor has seen better days. I'm running out of ideas to supply you. However, you may want to read through the troubleshooting guides in the FSM to see if we have been overlooking something. I just can't help but think there is something electrical involved since it dies and will run 5 minutes later. It's like something is cooling down after overheating. It would be great to monitor the coil voltage with an oscilloscope to see if anything shows up then.

[Captain Obvious]

So the car started it's life as a 260 with a manual trans, right?

Who swapped out the original flat tops for the current round tops? Did you do that swap, or was it like that when you got it? Also, how much of the original 260 stuff remains now that you're running round tops? Did they swap to 240 intake manifolds and balance tubes too, or are you running the original 260 stuff there?

I'm just trying to get my bearings... Got any engine bay pics?

[Rill Cosby]

Check the transistor ignition box in the passenger footwell to see if it's heating up. If so, turn a can of air upside down and spray the box so the liquid hits the box and cools it off rapidly. See if the car restarts easily. Unfortunately Nissan only provided directions to test using a testing box. There is this thread (http://www.classiczcars.com/forums/electrical-s30/49087-datsu-260z-transistor-ignition-system-service-manual.html) that says there is another testing method. You could PM DRBall to see if you can get a copy of it.

You may have been right on the money after all. I decided not to give up on the electrical side of it just yet. I pulled out the transistor box completely, removed the back side this time and started running the vehicle. It stalled out as normal but when I would try to crank it over, it would actually start and die right back down. It did that every time now. So I repeated the process but this time blew air on it after it wouldn't start. Started right up. So I put a blower on the box and it idled for over ten minutes until it stalled out but it started right back up at the turn of a key. I even took a video of the process because I couldn't believe it haha. Of course, the idle is still a little jumpy but it runs, still running as I type this.

I just have no idea how this transistor box is supposed to function. I'll definitely dig into some research tonight. This is where I have no idea what I'm doing. Could that mean the box's internals may be bad or something external causing the overheating? I really have no idea what I'm talking about. I need to get my hands on a multimeter.

Edited September 18, 2013 by Rill Cosby

[SteveJ]

If it's on its way out, I think you might be able to use an HEI as a replacement.

[Rill Cosby]

So the car started it's life as a 260 with a manual trans, right?

Who swapped out the original flat tops for the current round tops? Did you do that swap, or was it like that when you got it? Also, how much of the original 260 stuff remains now that you're running round tops? Did they swap to 240 intake manifolds and balance tubes too, or are you running the original 260 stuff there?

I'm just trying to get my bearings... Got any engine bay pics?

I believe so.

The previous owner switched to the Ztherapy round tops. Everything else seems to be original. N36 intake manifold and balance tubes. Some emission deletes. The previous owner was amazing with including just about every single part he did remove and include it with the vehicle along with some spare parts.