I have a '75 280Z with terrible gas mileage. I was getting 21-22 miles per gallon, and now am down to 12-14!!

I've changed the fuel filter, plugs, cap and wires... took the vaccuum hose off the top of the valve cover and the engine died... (am I checking compression properly?)

I am (at best) a novice mechanic... the "Z" has been in my wife's family and now mine for about 25 years now and I really want to "save" it.

I know loss of fire, loss of fuel, or loss of air equates to loss of power... I have fuel (using a LOT of it), I think I have the right air, and I know I have good fire (spark). HELP PLEASE!!!

Additional thoughts... the engine is nowhere near as reponsive as it used to be (about two-three months ago)... before, I'd depress the accelerator and the engine responded immediately and the car sped up immediately... now, I can depress the pedal all the way to the floor going up a hil and STILL lose acceleration.

I really don't know what else to do besides go to a garage, and THAT will be difficult to convince my better half to release the funds for... ahaha

Any help is MOST appreciated! Thanks in advance!

Ken

 

What color is your 280Z? Is it gold?

 

Orange... any ideas on how to help me with the fuel efficiency?

 

The hose on the top of the valve cover doesn't do anything for checking compression.
You need that attached. With it off, you crease a large vaccume leak after the air flow meter. So make sure that hose is attached and all the other hoses around the intake are in good.
If you have a California car, you might have an oxygen sensor. Replace that.
Check your fuel pressure if you have a proper gauge. If you can't you might want to just replace the fuel pressure regulator. That can get stuck and leave the car at a higher than stock fuel pressure. Mine did that. Once fixed it'll keep the fuel mixture down to proper levels giving you back your MPG and some more power. Hope this works for you!
I have attached a picture of the location of the fuel pressure regulator

I know a guy named Ken with a gold '75 280Z. I guess you're not him.

 

Thanks for the advice... I'll be sure to follow up on it. Question... my car is in California... where would I find the O2 sensor? I figure in the exhaust line somewhere....

I sincerely do appreciate your advice... and the picture printed well!!

My email address is not reflecting on my profile...

midway41usn@yahoo.com

Thanks much!
Ken

 

Is your car EFI? My car started doing this too about a week ago. Loss of power and bad fuel economy. I dicovered that my injectors were not opening in 2 of my cylinders, so i was only firing 4. Turns out the electrical plugs to the injectors were so corroded that they wern't working. I just orederd some new plugs and will get them put on. is only costing about $35 to replace all 6. I would wiggle your injector plugs ans see if your engine starts running better. Pull off the plug wires and see if it makes a difference in how the engine runs. If its no different, you probably have a malfunctioning injector.

 

the oxygen sensor is on the exhaust manifold. There should be one wire running from the intake down over the edge of the intake manifold and under it. It connects to a little cylinder that screws into the manifold. That is the O2 sensor.

 

Also check your water temperature sensor. My '78 280Z was running rich with horrible gas milage. Finally, the WTS failed completely and the engine would hardly run and eventually flood. I got a WTS off a junk yard 280ZX and tested it in a pot of water on the stove, a thermometer and a multimeter. This one checked out just like the service manual indicated it should. The car runs better than ever with the new Water Temperature Sensor.