1977 280z possible EFI Problem?

[zeeboost]

I've had issues with an L28 running so rich that it would foul out a spark plug...it was typically just one at a time for some reason. There's a chance you may have something going on with the injector, but I would get the running rough / surging issue ironed out first, since cleaning the spark plug seemed to remedy the misfire you were hearing in the exhaust. Slightly possible #1 injector is fouling out cylinder one, causing a richer condition that O2 sensor is picking up and having the ECU lean the mixture to compensate...but I think that's a far cry.

Let me know what type of meter you have and I'll see if it has a function you can you to try and measure pulsewidth. It may not give you an exact number in milliseconds, but could give you a percentage to go off of. I typically use a labscope for drivability issues on these cars, but more-so for backprobing the ECU and monitoring inputs vs outputs, so unfortunately don't have a good (cheap) tool recommendation for that off the top of my head. However although it's not a scope, a cheaper tool that I've used to measure pulsewidth is the Power Probe IV Amazon.com: Power Probe IV w/Case & Acc - Red (PP401AS) [Car Diagnostic Test Tool Digital Volt Meter ACDC Current Resistance Circuit Tester Fuel Injector Tester] : Tools & Home Improvement .  

Edited September 28, 2022 by zeeboost

[siteunseen]

I would put a threaded plug in that hole you see the block off plate through. Also the hole under the intake is the pcv valve. Does it have the valve? Those are 2 unmetered air openings you don't want.

[ckurtz2]

@siteunseenPCV valve is in and working well. Actually was one of the first things I looked at. The PCV valve is at the center of the intake, not near where those EGR connections were.

Anyways, by sheer luck everyone I believe I discovered the issue. I think there is a broken lead in the harness at the AFM connector. The connector is solid on the harness, however, when I wiggle the harness directly beneath the connector the engine either dies, stumbles, pops out the front, or surges. In other words, I got it to display all of the lovely issues the engine had. 

Funny cause somewhere in this thread I said that the "AFM connector is solid". Goes to show that you really have to pay attention to the little things on these cars, and not assume it's fine. Even if it was before. 

Now I am not 100% positive the AFM is the problem, because I have not gone in to try and fix it, but I am about 90% sure.

Here is a video proving my point!

 

Edited September 28, 2022 by ckurtz2

[ckurtz2]

Took off and then apart the old connector. Nothing loose nor viseably wrong. 

I had a quick disconnect AFM connector on the shelf from a long time ago. I was just too lazy to wire it in before. Wired in the new connector plugged the car all back up and it started up on the first crank. No surging, popping out the intake or exhaust, etc. Took it for a few mile test drive and drives like a dream all the way to redline:)

Thanks again everyone for all the ideas and support!

Glad it ended up being this over any of the dozens of other possibilities it could have been.

 

[kickstand80]

Oops, Glad you got it figured out! Free/cheep is always a good fix.

Edited September 29, 2022 by kickstand80

[kickstand80]

Check out the first response to your post! AFM and CTS.

My 83 gave me 7 weeks of the same thing you just went thru. I purchased the car as a non-running car for 3,000.00 after the PO spent 8,000.00 at 2 different shops trying to get it to run. This is the car and all I had to do was wash it.

With there not being any way to test the actual ECU's in these cars it can be a difficult and frustrating road. Mine ended up being the ECU.

Edited September 29, 2022 by kickstand80