I have a feeling that this has been posted before, but I can't find the thread for the life of me.

My Z has been running great, no problems at all. I drove it for about 4 hours straight just over this last weekend without any problems. Today, temperatures are hotter than they have been all summer (106 today) and when I went out to take the Z for a drive, she started up but sputtered a little bit. I got on the road and went driving, but the car still seemed to be hesitating. I pulled into a parking lot, got some food, and when I came back out, the car did not want to idle smoothly. I shut the car off, and when I turned the key back to the on position, the tach was sitting at 1200 rpms without the car even being started. I started the Z, and the tach indicated the motor spinning at 2500 rpm, when it was really idling more around 600 rpm, and very roughly.

Under load the car seems to run ok, it still seems to misfire, but it's really bad when I just let the car idle.

What could my problem be? I've got a freshly rebuilt engine with about 2500 miles on it, a pertronix pointless system in my dizzy, and that's pretty much it that isn't stock.

Help!

So, after thinking about what could cause a problem with the tach reading incorrectly and reading that the coil can cause fals readings, I decided to replace the coil yesterday. I bought a Niehoff coil from Kragen, and reused my old ballast resistor. It's not as hot as it was yesterday, I think temperatures are around the 90's today. I went outside to drive my Z on my lunch break, and it started up and seem to run more solid, but yet when the key was in the on position and the engine was off the tach was indicating the motor at 200rpm with the engine off.

What else can I replace? Could the ballast resistor be causing these remaining problems?

Or the Tach itself could be suffering from Heat Exhaustion.

There are a couple of electronic components (capacitors, diodes) that don't fare well over time and heat. Once they start to go, they need to be replaced.

That's why you see those cans of compressed air on electronic benches, to "freeze" or cool off the components known to fail under heat. If the item begins working properly, then it's the component.

HTH

E

Now what would cause the car to run poorly in the heat?

Vapor lock? I haven't encountered it personally, but Z's are notorious for it. Try searching the forums for it.

As far as running poorly in the heat, what is your fuel pump/delivery set-up? Are you running a mechanical or electric pump, fuel lines insulated, heat shield installed, etc.? The supplemental electric pump was added to many Z's by dealers to try and solve similar problems to yours in hot climates. I'm fairly new to the Z's, but fuel delivery seems to be the cause of a lot of hot weather, poor performance issues.