I have an 83ZX N/A that has problems starting and running first thing in the morning. I'm near Dallas and the temps here aint really cold but this car hates to start up and wont rev until it's idled for a couple minutes. Will not run right until it's fully warmed up.
I've checked restitance on the coolant temp sensor, CHTS, and I've checked the connections to them. I'm running about 12 degrees base timing with almost new NGK plugs and wires, new cap, rotor and coil. Also new o2 sensor. All vacuum hoses have been checked and/or replaced. TVV was bypassed because it was broken.
I haven't checked to see if the cold start injector is working but I'm told that in a warm climate like Texas it's not really needed. Is 60-70 degree mornings too cold for it not to run without it? I'm also told it only works during cranking anyway which jibes with what I'm seeing in the wiring diagrams in the FSM.
Once it's warmed up it runs great over 1500 RPM but it chugs real bad below 1500 and then it starts cutting out at 4000. The high rpm cut-out I'm sure is a seperate problem but who knows.
I'm thinking this whole cold running thing and chugging under 1500 is related to timing advance but I'm betting that several people out there have run into this problem before and can point me in the right direction and save me several hours of chasing ghosts. Thanks in advance!!!

 

Well, the cold start valve and air regulator aid in cold starting... so... take your pick.

 

I did check power to the air regulator and installed a new connector but I'm not positive its working right because there's no change when its disconnected. I need to investigate that further.

 

You are right the cold start valve only fires when the key is in the start position.

So if the car is driven and at operating temp it restarts and runs great?

It sounds like it is starving for gas. Maybe the pressure regulator? I'd check the pressure anyway both hot and cold.

Also check all your vacuum lines.

I also think the ECU has a different fuel injector ratio between cold and hot.

Wish I could help you. It took me 2 yrs (working on it on and off) to figure out why my 280 wouldn't start. Turned out to be a bad ground to the ECU. Strange problems like these can be a bi tch.

 

Once it's warmed up it runs good and fires right up every time. I've run it with a fuel pressure gauge on the window and it has good pressure at all times and the pressure regulator works as it should.
Haven't had time to find out how to test the air regulator which could be a problem. I'm leaning more towards the electrical advance in the dizzy or bad signals to the ECM from the coolant temp sensor or CHTS.
But, as I said before.... theres no noticable change of any type when I disconnect the air regulator. Same goes for the elec. advance at the dizzy.

One question though??? Am I reading the elec. diagram correct, that the cold start injector and the thermotime sensor get their power from the same circuit (yellow wire) that goes from the ignition switch to the starter? This was originally an automatic and I have yet to locate where the inhibitor switch was to see how that was bypassed so maybe that's why the cold start injector doesn't get any power.

 

Have you always had this problem since you owned the car?


double check the CHTS.

 

I've always had one problem or another that's related. I've eliminated all real issues but this one. I think the AFM was tampered with and I've been making minor adjustments to the spring tension with mixed results. What works best cold doesn't work well warm so I got it set where it runs best when warm. I'm pretty sure it's the air regulator not working.