81 280zx running rich, backfiring..Need advice

[dcooper23]

Any help here would be HIGHLY appreciated!!

 

I picked up an 81 280ZX 5 spd N/A and was told it had been sitting for about 2 years and needed a fuel pump.

 

I installed a new fuel pump, drained all the old gas, put new gas in and got it to start and run, but it runs like shit.

 

Looked under the car after it had reached normal warm temp and the catalytic convertor was glowing orange so I figured it must be stopped up so I cut it out but it didn't help it run any better.

 

So, I changed the oil, put a new set of properly gapped plugs in it. Runs and sounds a little better than before, but still not right.

 

I noticed that the SOLID RED check engine light stays on. If you give it any gas, it mostly just sputters and backfires for about 5 seconds but then it will clear up all of a sudden and rev up to 4-5k rpms and sounds like its hitting on all cylinders. (I should note that I noticed that the yellow FUEL light stays on until right as soon as I can get it to clear up from sputtering. It flashes off and the car revs right up, but backfires when going back to idle..

 

I have checked many switches and connections. I noticed the thermotime switch was partially broken and the connector was it terrible shape, so I replaced both but it hasn't made a difference.

 

I unplugged the CHTS while the engine was running and it immediately shuts the engine off. Im assuming that means that its ok...??

 

I found one small vacuum hose that is attached to the very rear of the intake manifold on the driver side that has been disconnected on end, but cannot tell where it originally went. Also, capping this hose with my thumb while the engine is running did nothing.

 

Any ideas on what I should do next? Coolant temperature sensor? The car warms up normally and does not overheat. temp gauge seems to be working fine

 

I listened to all the injectors with a stethoscope and they are all ticking away when the car is running.

 

Any advice here will be appreciated....Thanks

[flatts57]

I've been reviving my 81ZX that has sat for several years & am making progress. My fuel pump was frozen so it was pulled, disassembled, & cleaned. The fuel filter was plugged & couldn't blow air through it, replaced. Replaced several old fuel lines at the fuel tank & filter area and have good fuel pressure now. The injectors were frozen so put Marvel Mystery Oil in the fuel rail, pressurized, hot wired each injector while heating with the heat gun. I suspect I need to run some fuel with detergent through the system before all will run smoothly. Next I had a spark problem. Checked my notes and had never replaced the plug wires which were reading about 15k ohms, replaced. Started running ok but not smooth. Then I started having loud ticking noise.  This has happened several times and each time it has been a lash pad being thrown off the valve probably a sticking valve situation. I've got Marvel Mystery Oil in the oil now hoping this will soon stop. The last incident was a loss of manifold vacuum, down from 19 to about 10"Hg at idle. This was a lash pad that rotated 90 degrees and was holding the #2 intake valve open. Found it when I was checking all of the valve lash. I adjusted the valve lash on four valves while I was at it and the last run was pretty smooth. Now I think I just need some miles to work the detergent through the fuel and oil systems. Over the years I've had some connector problems under the hood. At present, all of the connectors on the fuel injectors & cold start valve, & head temperature, have been cut off and soldered on. This has helped allot for reliability.