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

[mbz]

SORRY - I THOUGHT I WAS LOGGED IN AND POSTED THIS AS A GUEST.

ADMIN PLEASE DELETE THE GUEST POST AND USE THIS ONE.

 

Need some help on what to do next, here's the story so far.

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.

Engine runs very rough for about 1-3 minutes at high RPM when gas pedal is pressed, and exhaust kicks out white-ish / light gray fumes.

When gas pedal is released, engine dies, car will not idle.

Try to start again and engine cranks but will not start.

Let it sit for 1-2 hours and it will start again, same as above.

Makes me think it is flooded with gas and needs to sit before it will start again, but not sure.

Reviewed service records and saw that several basic maintenance has not been performed for a long time (anywhere from 2 years - fuel filter, to 8 years - spark plugs & air filter).

Here's what I have done so far:

Replace fuel filter.

Replace air filter.

Replace spark plugs.

Replaced fuel hose from tank to fuel pump (found it had a couple of gashes, but not dripping gas.... figured it should be replaced).

Replaced air regulator hose (appeared to be original equipment that was dried and appeared to have fresh crack in it).

Adjusted idle screw (tried 2 turns counter clockwise, no affect. tried 2 turns clockwise, no affect. set it back to original position.)

Did visual inspection of air and fuel hoses.

Tightened up all connections.

Inspected carbon canister, replaced under filter.

 

Anything I am overlooking?

Anything I left out in the problem description?

Any advice on what to test next?

Edited March 17, 2019 by mbz

[Zed Head]

What does the white smoke smell like?  Have you inspected the spark plugs?

How high is "high" - "very rough for about 1-3 minutes at high RPM "?

Give the ECU a sharp tap or two and see if things change.

 

[mbz]

The smoke smells like car exhaust. Not gassy, not oily. Just like a large amount of exhaust.

Yes I pulled the old ones and replaced. Same problem persists with new spark plugs, it just fired up faster.

High RPM is between 2000-3000

Hmmm, tap on the ECU? Really?

Can I ask why before I do it?

---------------- a few minutes later ------------------

OK so I just took the kick panel off the ECU so I could tap on it and I found these 2 white wires just hanging there. (see photo)

Any idea what these are for and if they are supposed to be connected to something (or each other)?

Edited March 17, 2019 by mbz

[siteunseen]

Squeeze the fuel lines in the engine bay to see if they're hard. With a good fuel pressure regulator and fuel pump they should be pretty hard to pinch or squeeze while running.

There's been many gremlins fixed by wrapping the ECU a few times, not too hard though. 

Edited March 17, 2019 by siteunseen

[mbz]

Yes, fuel line seem stiff, but I'm planning on testing fuel pressure next weekend to be sure.

That was next on my list of things to check.... the fuel pump.

But it stands to reason that fuel pump is working fine if engine fires up and runs for a few minutes while foot is on gas pedal.... no?

Also, see photo above regarding 2 white wires found unattached behind the ECU kick panel.

Any thoughts on what they are and if they should be attached to something??

Edited March 17, 2019 by mbz

[Zed Head]

28 minutes ago, mbz said:

The smoke smells like car exhaust. Not gassy, not oily. Just like a large amount of exhaust.

Yes I pulled the old ones and replaced. Same problem persists with new spark plugs, it just fired up faster.

High RPM is between 2000-3000

Hmmm, tap on the ECU? Really?

Can I ask why before I do it?

---------------- a few minutes later ------------------

OK so I just took the kick panel off the ECU so I could tap on it and I found these 2 white wires just hanging there. (see photo)

Any idea what these are for and if they are supposed to be connected to something (or each other)?

mbz, the more detail you can give the better.  If you just describe what seems important to you then our brains can only go as far as your brain.  Tell us the stuff that seems worthless.  "Exhaust" isn't good enough.  Does it smell sweet, like coolant?  could be a head gasket.  Has it overheated recently?

I said "inspected" the plugs, not replaced.  How did they look?  Were they wet with gas, or clean like they've been washed with coolant?  Were they all the same or were one or more different?  Details.

The white wires are for testing.  They just sit there, doing nothing.

So, you are holding RPM at 2500 for two solid minutes (that would be a long time) and it just pours white smoke?  You said "kicks out".  Don't know what that means.

No offense intended.  Just need a better idea of what's happening.  Does your car have a catalytic converter?  You're in CA and they were the first to get them.

[mbz]

Zed & site, diagnosis help much appreciated!

Exhaust does not smell like coolant, it smells like gas.

Head gasket is clean, no leaks. Last replaced in February of 2010. About 11k miles since head gasket replaced.

Car has not overheated since I have owned it. I have driven it about 125 miles. First drive was an extended drive (75 miles) in Friday rush hour freeway traffic. No overheating.

Yes car has catalytic converter, was last replaced in March of 2014. About 7K miles on new Cat.

Battery is 10 years old. About 15K miles on current battery. Charge seems OK. When it was towed home 2 weeks ago upon initial onset of trouble, AAA tested battery and alternator. Results are

Battery Test: 669 CCA, it is rated for 675 CCA, temeprature was 60° F, voltage was 12.36V.

Starter test: Cranking normal. Voltage 11.97V, Time 10mS.

Charging system Test: No Voltage. No Load: 12.72V. Loaded: 12.69V

I have video!!!!

Tapped on the ECU as suggested then started the car.... it idled this time for several minutes.

Idle is rough, however this is the longest it has idled (about 3-4 minutes). It ran longer than the video shows (see video 1).

Opened throttle, then let go back to idle and car dies (see video 2).

Try to start engine again and it won't start. (see video 3).

See old spark plugs in attached photos. They all look the same. Black, not wet, a bit worn out.

 

[madkaw]

Those are fuel fouled for sure. You need to test fuel pressure . Then start checking all connections. Read the EFI BIBLE , and get your multimeter out. 

Your pushing your luck with a 10 year old battery - regardless out how it tests.

I don’t see anything about ignition checks ? Dizzy cap? Plug wires? Rotor? Timing ?

[Dave WM]

EFI section of FSM is key, you must read read and read again until you understand everything about how it works.

Plugs clearly so rich, OR are the an incorrect heat range, guessing rich.

common thing causing rich

• incorrect fuel pressure (too high), defective FPR could even be leaking raw gas into the manifold.
• defective or incorrectly connected water temp sensor
• Leaking injectors/stuck injector/defective cold start system (injector or thermotime switch).
• AFM, if been prior monkeyed with, a common thing as its just too tempting to go mess with it.
• ECU (diagnostics are if everything else is ok, then its got to be the ECU, but you really really need to eliminate everything else).

as a start, fuel pressure, then listen to injectors to make sure they are all clicking, then pull the cold start and make sure its working properly. I will not go into the specifics that is what the FSM is for on how to test all the systems.

It does not make since that the idle adj is not working. it should slow down CW speed up CCW, its an air bleed that bypasses the throttle plate.

 

 

 

Edited March 18, 2019 by Dave WM

[mbz]

Madkaw, thanks for the advice.

At this point, my weekend time to trouble shoot car is done, but I am trying to narrow down what I should look at next weekend.

I agree on the battery, but I want to get stable start and idle sorted first.

Yes I have EFI manual (thank you calssiczcars) and have been reading it.

Doing the routine maintenance stuff seemed like the first logical step and it needed to be done anyway (fuel filter, air filter, spark plugs, and found a fuel hose and air hose the needed to be replaced while I was poking around).

I'm leaning towards checking fuel pressure / fuel pump as the next step in trouble shooting and I guess I'm looking for guidance/agreement from the group before committing to that as next weekend's project.

If that checks out, then air intake/throttle system seems like the next logical step.

Am I on the right track or missing the point completely?

The one thought that is nagging me is that the rough idle makes me think there's a misfire, but.....?

[mbz]

DaveWM, solid thinking.

I'm right there with you on that.

Testing fuel pressure and listening to injectors next weekend.

Service records indicate fuel hoses and fuel injector seal kit were last work performed in July of 2018, about 150-200 miles ago.

[Dave WM]

Number one issue on rich running is the water temp sensor, not the sending unit for the gauge but the one that tells the ECU how cold the engine is. The FSM tells how to check and what reading to expect for given temps, Test at the ECU 36 pin connector with a good volt/ohm meter.