It's been awhile since I've done anything with the Z due to some bad stuff going on with a family member, but to refresh, I have a 75 280, 79 ZX dizzy with E12-80 module vacuum advance disconnected, Crane coil no ballast, AFM calibrated per Atlantic Z, fuel pressure 36-38 at idle w/o vacuum 32 with vacuum, all new fuel lines and clamps, timing at 15°, new CSV, new CSV, thermotine checked out OK so did the TPS(by the Bible). It starts and runs well, but stumbles at about 5800(timing I'm thinking), problem is it runs rich as hell gets about 10mpg(50 miles on 1/3 tank), plugs are sooty black and black soot at the exhaust. I've adjusted the AFM as much as 12 teeth to lean side after fingering the AFM and no difference, the AFM measurements by the Bible show its off about 12%. I'm at the point of junking all of it and either 1) sell the car for parts or 2) dumping $1000  into carbs. Any help would be appreciated. Thanks for all the past help for all of you.

Mike

Edited March 18, 201510 yr by mjr45

What about the all important CTS?  You did not indicate testing that.

 

Also, double check you did not switch the plugs for the CTS & thermotime.....

You didn't mention the most important component, the coolant temperature sensor.  And 32 psi is kind of high at idle, have you checked the FPR for leakage?  See if there's fuel in the vacuum hose.

 

With that gas mileage, the first tow things I would check are the coolant temp. sensor and the FPR.  I had a similar problem, it was a bad FPR.

 

And check your coolant sensor readings at the ECU connection.  Then you'll see what the ECU sees.  Get real resistance values and know what temperature the sensor is at.

 

Also, vacuum advance helps gas mileage.  Disconnecting it is a mistake.

Plus, the beer can method on the atlanticz site would be "calibrating".  Turning the wheel to make it leaner would be "screwing it up".

Drink more beer then calibrate!

The FPR is new and I forgot to add that CTS is new and checked out correct by the Bible. I did the "beer" can calibration of the AFM and as stated it is out of spec by about 12% per the bible and you are right messing with "wheel" in the AFM is just screwing it up, but that was a last resort to try to get it to lean out. The only other question in my mind has to do exhaust, the guy who did the exhaust put a 2" pipe from the header back to the muffler which he put in the tranny tunnel and then for whatever reason ran a 1 1/2" from the muffler back to rear end. I know that logically that setup should increase back pressure but I don't think it should effect the rich/lean  of the EFI. Just for grins, I switched the thermotine and the CTS wires, car ran like crap.

 

I also have a 3rd option, fill the gas about ahlf full of black powder and light'er up!

 

Blue, I try to drink all the beer I can when working on the beast! Maybe that's whats wrong.

Mike

Edited March 18, 201510 yr by mjr45

Lets look at what can make a car run rich:

Fuel Injectors:

- wrong type

- leaking

Fuel Pump and FPR:

- pressure too high

AFM

- spring too weak

- air temp sensor failed

- electrical connections corroded

- faulty connections inside

- wrong type

Throttle Valve Switch

- electrical connections corroded

- stuck on WOT position

- not adjusted optimally

Coolant Temp sensor

- electrical connections corroded

- electrical connections open

EFI Harness

- corroded connections

- broken/open connections

- bad ground

ECU

- malfunctioning

- wrong type

- corroded connections

Electrical system

- low voltage/high voltage

Ignition system

- weak spark

You could replace the temperature sensor with a fixed resistor to rule it out. 320ohms will do the trick.

Make sure you have clean NGK or Denso plugs

Also

Two words....Triple carbs! 

Two words....Triple carbs! 

Nah... he want a fuel system that was at least invented in the last two centuries.

 CTS is new and checked out correct by the Bible. I did the "beer" can calibration of the AFM and as stated it is out of spec by about 12% per the bible 

I'm not familiar with any AFM measurements in the FSM or the Guidebook except resistance of the carbon trace.  And that's not affected by the "calibration".  Do you mean your resistance numbers are off by 12%?  What are the numbers?

Sorry to hear about the continued troubles. Are you sure you're using appropriate injectors? And have you ever tried another ECU just to see what happens?

 

Wish we were closer together, I'd be happy to do what I could to help.

 

 

The FPR is new and I forgot to add that CTS is new and checked out correct by the Bible. 

Did you check at the ECU connector?  Or just the CTS itself?  You could have a perfect CTS, that's worthless if it's not connected to the ECU.

 

Make a list of all of the parts, and all of the test results, and post it.  Something will show.  The right parts, with the right numbers, and it has to run right.