1976 280z engine runs rough then dies, will not idle.

[Dave WM]

a couple things on that vacuum reading, the 17" or higher, that will be on a warmed up engine, I noticed mine is about 15" right after startup, works its way up to about 17".It also presumes an optimal running engine (highest RPM for most closed position of throttle plate). Ign timing will effect it as well since that again effect over all efficiency of the engine as an air pump. I am not surprised the vacuum is not as good as it should be given the poor state of the A/F mix.

He is down the normal A/F mix problems we all suffer from after drift of sensors/corrosion on a open loop EFI system.

[Dave WM]

oh forgot to ask, are you still having NO effect with the idle adj? that one reduces idle CW increases idle CCW, its an air bleed system not a throttle plate position set.

Also did we ever address the AAR its sort of a idle up air bleed for when the engine is cold.

But the real problem is still the excess fuel anyway you cut it, badly carboned new plugs after a short run would tend to say the EFI is allowing too much on time for the injectors.

[Zed Head]

1 minute ago, Dave WM said:

Ign timing will effect it as well since that again effect over all efficiency of the engine as an air pump

Since it seems that the PO's mechanic might have "hacked" some things to get it to pass emissions, a new plan might be in order.  A basic tuneup maybe.  Confirm initial timing at idle, confirm valve lash is set correctly.  Have cylinder pressures been measured yet?  Has the cylinder head and block combination been confirmed?  There is a low compression ratio NA engine floating around out there that we helped a guy put together.

It would be nice to see a summary of engine specs and actions taken so far.  Cylinder head, block (the engine serial number should match the plate on the fender well).  Too many pages to go back through the whole thing.

My 76 has a 78 engine in it and a bunch of other minor mods.  You never know what the trail of PO's have done.

From Post #1 - "1976 280z California edition (manf. date Sept.1975).

Bought the car in late Jan. 2019, car passed emissions test and it started and drove fine until 2 weeks ago when problem first occurred."

[mbz]

All good threads must come to an end.... even though this thread was not so good, it's time has come.

The issue is fixed and DaveWM gets the kudos for figuring it out. (Dave "Z Oracle")! ??

Thank you for your methodical approach and patience while this got sorted out.

The issue was the cable from the bullet connectors to the Water Temperature Sensor connector. (not the WTS itself).

A $6 replacement cable from AutoZone fixed the issue and the car is running better than ever!

Thanks again everyone for your help!

Much appreciated and I'll reach out next time I need expert advice!

[Captain Obvious]

Excellent!!      So maybe all of the fuel pressure stuff was a red herring caused by questionable test equipment and procedures?

In any event it reinforces the belief that it just looks like most other old 280Z's that are running either really rich or really lean because of a whole bunch of interrelated issues like dirty connectors, improperly placed connectors, and vacuum leaks.

So you found the first, highest priority of those, but there are probably others of lower contribution and impact. The remaining issues are probably what the previous owner's mechanic was chasing to get it to pass smog.

[mbz]

36 minutes ago, Captain Obvious said:

So maybe all of the fuel pressure stuff was a red herring caused by questionable test equipment and procedures?

Absolutely! The equipment was faulty, however I think the procedures were sound as they yielded good results with different equipment.

36 minutes ago, Captain Obvious said:

So you found the first, highest priority of those, but there are probably others of lower contribution and impact. The remaining issues are probably what the previous owner's mechanic was chasing to get it to pass smog.

Exactly! I don't think the PO's Mech. did anything wrong or dubious or acted with malintent. Quite the contrary, he's a solid mech. that was doing what his client paid him to do... get it to pass smog and sell it. The PO's Mech. is actually a pretty solid dude with a wealth of Z knowledge and experience. I've spoken with him several times and he's given me the full service records going all the way back to 1976. I don't find any fault with him, he's trying to run a business and a good one at that.

Like you said C.O. it's just an old Z and these problems come with these cars. Case in point, yesterday I "fixed" the inspection lamp... the bottom just needed to be cleaned so a solid ground connection could be made (I still need to fix the toggle). I'm sure I will find many more electrical connections and hoses that need replacing.

I'll be monitoring the running rich issue more closely now, I want to ensure it will pass smog EVERY TIME. The good news is, I have about 2 years to sort it all out! ?

Edited April 21, 2019 by mbz
grammatical

[Captain Obvious]

So when the temp sensor input is actually making it to the ECU, how does it run? How do the plugs look?

I'm a little concerned about the pic you posted of the insides of the AFM. Since you have a good report with the PO's mechanic, can you (did you) ask him if he adjusted the AFM to try to lean things out?

[Zed Head]

On 4/14/2019 at 4:15 PM, Zed Head said:

The checklists in this book will tell you a lot.  Good news on the FPR, although you do have an extra one now.  Weird that you know what I'm cooking for dinner...

Sorry, couldn't resist.  One last dig...

 

Edited April 22, 2019 by Zed Head

[mbz]

2 hours ago, Captain Obvious said:

how does it run? How do the plugs look?

It's running good, I pulled the plugs this morning and they look kinda white/grey at the tips, not black like before when running rich.

2 hours ago, Captain Obvious said:

Since you have a good report with the PO's mechanic, can you (did you) ask him if he adjusted the AFM to try to lean things out?

Not yet, but it's on my list of calls this week. That thought crossed my mind and I do want to know what he did so I can "UNDO IT" if needed.

Happy Easter all, thanks again for the much appreciated help!

Edited April 22, 2019 by mbz
Being nice to Zed.

[Zed Head]

At least you're more honest now that your problem is fixed.  You were hedging your comments when you needed help.

Good luck with it.

[mbz]

3 minutes ago, Zed Head said:

At least you're more honest now that your problem is fixed.  You were hedging your comments when you needed help.

Good luck with it.

OK Zedd, I'll play nice and make a deal with you....

I'll take down the picture if you stay off my threads, and I'll stay off yours.

Sound fair?

We can be like 2 ships passing in the night.

Edited April 22, 2019 by mbz

[Zed Head]

I shine pretty well in this thread.  Your appearance is up to you.  I didn't quote you so it's gone once you edit.  Your call...