'81 zxt 2 problems driving me crazy
 

I hope someone can help with these problems. I don't think they are related but I hope someone knows. I have an 81 280zx turbo that backfires and sputters like crazy but only when the engine is cold. It idles fine with just a tiny miss now and then. The second problem that just started is when I turn on the heater or ac the engine goes nuts. The engine looses power and the tach jumps all over the place if I'm on the highway @ 65 the tach goes from 3400 down to 2000 back and forth. Putting it in nutral and coasting for a bit usually stops it for a while but it does come back. I'm out of ideas, hope someone can help.thanks

Welcome to ZDriver!

First, download the FSM if you haven't done so yet (XenonS130 - 280ZX FSM Downloads).

Let's start with the basics:
Did these problems just start up all of the sudden?
When was the last major tune up? (plugs, wires, cap, rotor, coil, total check over of sensors & connections)

A full tune up / check over will do wonders for a tired motor.

re: 2 problems
 

up

Hi, the backfireing when cold has been for a long time, the other with turning on the heater has just started about 2 weeks ago.
I did a major tune up about 3 months ago when I replaced a worn out turbo. I've replaced almost all of the sensors, o2, temp, oil sender, head temp, throtle position,etc. I've even replaced the ECU. After doing the turbo replace
the backfire when cold seemed to go away for a while but is back with a vengence. The turo blew due to a clogged cat which has been removed. The car only has 73,000 miles on it.. Thanks for your response..

I've done a complete tune up 3 months ago when I replaced a blown turbo. The turbo blew due to a clogged cat which I removed. I've changed most of the sensors head temp, detonation sensor, idle position, o2, etc. I even replaced the ECU, still the same backfire when cold. The heater switch problem is very intermitten. Once the engine is really warm it runs like a top..
I also have an ECCS analyzer wich shows everything OK. I'm stumped!

Did you rebuild the AFM yet? ECCS probably won't show intermittant faults...

Cold backfires
 

I replaced the AFM, tested all the sensors and they were right on the money except the coil wich I replaced. Did another tuneup, cleaned all the connectors. Took it out while still cold and the thing ran worse than before. While driving the tach was jumping all over the place and I felt the car surging, when I stopped for a traffic light I turned the heater switch on to low and the damn thing stalled. I drove for about 10 minutes and it started to run better after getting up to normal temp. After stopping at a store for 5 minutes I headed home and the thing ran like it just came out of the showroom, not a miss and turning on the heater had no effect. GOING CRAZY, PLEASE HELP!!

Bad connector or short
 

Sounds like a loose connection or short, hard to troubleshoot intermittent problems, since they seem random. I would try pulling the heater fuse for a while. I don't know how or why, but possibly when your car got the ECU upgrade that power for something is piggy backing on the heater circuit. At least if you pull the fuse it will eliminate the heater circuits influence. You might try pulling fuses on all non critical circuits, see how she runs, take good notes and start replacing fuses one at a time, might help narrow down your problem.