78 280z Severe Driving Problems

[kinser86]

A lot of good information here, let me see if I can answer them.

8 hours ago, Zed Head said:

Just watched your last video.  Very informative.   I don't think it's firing on all cylinders.  Could be several reasons.

I would confirm that firing order AND rotation direction are correct.

Check all of the injector connections.

While it's idling pull one injector connector at a time.  Each one should cause a change in idle speed.  Pull the connector, confirm idle speed change, put it back on.  If you find one that seems dead, switch it with the one next to it.  They all fire at the same time, there's no order.  If the problem follows the injector connector it's that, if not it's the injector.

We got way ahead of your actual problem I think, although everything you've done so far will probably help with the fine tuning.  But you need to get each cylinder firing first.  Another reason for cylinder misfire is bad cam lobes.  Could also be improper lash setting.  You might check your lash again and/or do another cylinder pressure check.

I went through an exercise believing the oil pump drive gear was off a tooth, so I spent a day going one tooth left and one tooth right to see if I wasn't seeing a true 11:25. This resulted in a waste of time because it was correct to begin with. This is before the injectors were rebuilt. I will take a picture of it tomorrow but 1-5-3-6-2-4 on cap to the plug is what I have.

When validating the timing marks on the crank pulley, I checked TDC on the crank/timing marks on cam gear/ear lobes on cam/piston at top of bore. The rotor on the distributor points towards the radiator, and at the number 1 plug outlet on the cap which also has the reference mark.

I just replaced all injector clips about 3in back from the originals. I used a screw driver to my ear in order to listen to each injector to make sure they were firing. They are definitely clicking, all at the same amplitude and frequency (to the best of my hearing capacity). I can try the unplugging method too and see if I notice an issue.

I've gone through the valve lash a number of times, my initial post is the measurements after the third time of going through things (going in circles?).

3 hours ago, Zed Head said:

Just watched the video again.  I wonder if the AFM is even plugged in.  You can check the pins at the ECU connector.  Sometimes the plug falls off the bottom when you're reinstalling the AFM.

Or maybe the TVS is stuck at idle setting.   Something odd going on, it sounds good with no load.

When I did the checks to the components, I did all the test through the ECU connector. I can check the conditions of the pins on the AFM connector to confirm they are not popping out when installed. I confirmed TVS works at all angles corresponding to the EFI-Bible. I removed the cap and made sure all contacts and moving parts were clean and free of any binding.

3 hours ago, Dave WM said:

forgot to ask, where those new plugs with only a few miles on them? I like to read plugs that are brand new. Regarding ZH comment, you should make sure you are getting the resistance test for the AFM at the ECU 35 pin connector, that would make sure the wire harness is not an issue. I still think you should focus on getting that fuel pressure issue resolved 1st, no reason for it to be high like you were seeing.

They have some miles on them. The values in my first post were measured at the ECU connector. I agree with FP statement. I spent more time looking for a faulty AFM or other things that this might be more of the culprit.

2 hours ago, Captain Obvious said:

There is lots of expert help already on the case, so I'm going to stay in the wings as much as possible, but before I go back to my hiding spot, there are two things that have caught my eye.

First is this... On your to-do list was to return the AFM gear to it's original position by turning it six teeth counter-clockwise. The implication of this is that you had previously turned the gear six teeth clockwise. (Haha! Big intellectual leap by me, huh?) The POINT is... If think you are chasing a lean condition, then turning the AFM gear CW will only make it leaner:

The second thing that caught my eye was the way you have the vacuum gauge and the vacuum advance connected. Something is wrong with the following:

The vacuum advance signal for the distributor is not supposed to come directly off the intake manifold. It is supposed to come off a ported source from the bottom of the throttle body. And that vacuum source should be zero vacuum at idle. So something is screwy there, and your fuel pressure readings and ignition timing numbers are suspect until you get to the bottom of that.

If you have the distributor connected directly to the intake manifold, then your base timing is wrong. Or if you have the vacuum gauge connected to the ported vacuum source, then your throttle plate is open waaaaaaaay too far at idle. Potentially because the thing just won't run at anything less. Also, if you're using that ported source for the gauge, then your FPR numbers may be correct because you can't do the subtraction for manifold vacuum correctly.

And I agree with Zed Head... It just don't sound right and I agree that you need to double check the firing order. Also check the injector clickety-clicking with a stethoscope.

Understood on the AFM observation, thanks for clearing that up! I believe the distributor is connected directly to the intake right now. I will confirm this but it might be hooked up to one of the ports near the FPR port. In that case, the vacuum reading in the video was coming from the intake and not before the throttle plate.

I will go over the vacuum lines and trace their origins as everyone has been pointing out.

So right now the to-do list is:

• Verify vacuum line routing (Distributor)
  • If incorrect, verify timing again (10°BTDC @ 800RPM)
• FPR exercise with hand vacuum pump
• Verify firing order (caps and plugs with pictures)
  • 1-5-3-6-2-4 CCW
• Verify AFM pins not popping out when plugged in
• Review injectors firing
  • unplug one at a time
  • screw driver to ear
• Record video of RPM/FP/Vacuum

If I am missing anything please let me know. I appreciate everyone's feedback. It is a lot to take in and I want to make sure the order of operations of the troubleshoot is correct, focusing on one thing at a time.

Edited September 1, 2018 by kinser86

[zeeboost]

I'm glad captain obvious picked up on vacuum signal to distributor. That should be ported vacuum, not manifold. If anything, disconnect the vacuum line from the distributor, plug it off and set base timing that way. Make sure your rpms are around 800 when setting it.

I honestly don't see 34psi at idle causing your sputtering problem. 153624 counterclockwise is correct, the 1 should be towards the radiator. 

You can run a fuel pressure drop test on the injectors, it's a crude test that doesn't show you spray patterns but can show you if an injector isn't moving fuel. Have your pressure gauge connected and with key on engine off run the pump for a few seconds, either clamp off the return or deadhead (cap off) the return side of the rail. If your fuel pressure doesn't quickly bleed down after turning the key off, you can probably get away without capping the return. Record where the pressure is at, then using a 9 volt battery, very quickly jump an injector (literally just tap the wire to the terminal) and monitor pressure loss. Do this with all 6 injectors and compare their results. You'll have to prime the fuel pump after testing each injector, and make sure not to activate them too many times before starting the engine (keep from flooding it). I use 12v when doing this but 9v is safer, as you can easily fry the injector by leaving it engaged too long. 

Lots of other things can be done but these will help. If you have an infrared temp gun you can hit each exhaust runner with it, a "cold" cylinder may be your problem child. Definitely easier with headers than log manifold, (and a setup that doesn't have an intake directly above it) but doable. This is just a suggestion if you have one handy, don't run out to go buy one just for this. 

[zeeboost]

Just read where you had the injectors rebuilt. Though I hate making any assumptions when diagnosing, probably a safe bet that they're fine. Though a little extra confirmation never hurt.

[jonathanrussell]

Hi. I think all of us with a 280z have been through the FI troubleshooting at one time or another. Clearly you know how to diagnose so it is hard to imagine pointing out something you haven't already thought of. I will share what I have sometimes found to be the culprit.

1) I am sure you have thoroughly checked for vacuum leaks but it might be worth trying again. The rubber air passage between the AFM and the throttle body is a common problem. Also, there is a thread on this forum where the intake manifold where the egr valve mounts had corroded and was causing a huge vacuum leak. Worth looking at.

2) You have been so thorough in testing the AFM that what I am about to suggest seems unlikely but I had an AFM that had been subject to multiple backfires and the flap had become bent a bit. This caused the flap to stick open which resulted in all air being metered the same. Car ran very similar to what you describe. Either way, if I had your car I would buy a spare AFM and test.

3) Looks like you have replaced your injectors but more often than not I find that old 280zs have terrible injectors. Often when I have tried everything else, even if the injectors are clicking, replacing the injectors does it because they are clogged. They click but don't flow, or at least not consistently. Again, this is probably not your problem.

4) I always keep a few Ebay ECUs around for testing, though I have to say I have never found an ECU swap to solve my problem. No doubt though sometimes it is the ECU.

FYI, I agree with suggestions in earlier posts too....get fuel pressure right, firing order, etc. I might lean toward trying a stock fuel pump and using the original pressure regulation device (assuming it is working). Naturally, you need to verify that you are getting spark to each cylinder but I am sure you have done that.

 

Anyway, I doubt this has been helpful but wanted to share a few things that have stood out for me with the 280zs I have worked on over the years.

Don't give up. At some point you will figure it out and with all of the great work you have done so far, and with your great compression numbers, I am guessing you will have a terrific running car.

 

 

Edited September 1, 2018 by jonathanrussell
typo

[Zed Head]

One area that has caught some people is the EGR system.  Since your engine sounds good at idle you might try disabling it to see if anything changes.  I think it actuates by ported vacuum so blocking that hose might have an effect.

And like jr says above, make sure that the AFM vane is moving freely.  When I was watching your video I thought I saw it hang, its movement trailing the engine sound, but I couldn't be positive when i rewatched it.  A slight delay in vane reaction will lean things out and cause intake popping.  And as CO suggested, if the AFM has been messed with maybe the atlanticz calibration procedure is the way to go.  I'd get a magnifying glass and see if I could find the original glue blob traces myself.  Or crank that potentiometer up and try to drive it.

Something will show up.  You're doing all of the right things.

[kinser86]

Alright here is an update.. We might be on to something but as promised let me check off the to-do list first.

• Verify vacuum line routing (Distributor)
  • If incorrect, verify timing again (10°BTDC @ 800RPM)

It was incorrect, vacuum source was after throttle body. I put it below the throttle body per the FSM. Timing/Idle speed adjusted back to 10°BTDC @ 800RPM.

• FPR exercise with hand vacuum pump

I left this tool at home so I was unable to perform this exercise! ? It stays on the list...

• Verify firing order (caps and plugs with pictures)
  • 1-5-3-6-2-4 CCW

As promised, pictures. Also a video of each lead with a new plug in showing spark.

• Verify AFM pins not popping out when plugged in

Pins are solid in the connector when installed. I still have the AFM cover off right now so those terminals are easy to access with a multimeter and measure to the ECU connector.

• Review injectors firing (I have video below)
  • unplug one at a time

#2 and #3 did not have an impact on idle speed when removed. I swapped connectors from Injector #1 and #2 after this, and when I perform the test again with the swapped connectors, #2 still has no impact on idle but injector #1 (with #2 connector) will drop about 90rpms like it did with the original connector.

• screw driver to ear

All injectors are clicking. #2 and #3 are clicking the same as other. Granted I am using a tall screw driver to my ear, when the connector from #2 or #3 is removed, the amplitude of the clicking goes down a lot. When the connector is installed, it has the same amplitude as the other injectors.

• Record video of RPM/FP/Vacuum

See video below.

So after this, I am really perplexed with #2 and #3 injector having minimal impact on idle speed.In the video you can definitely see about a 100rpm drop on all other cylinders. I have not been able to reduce idle speed yet but I forgot my vacuum pump to test the FPR. 

6 hours ago, Zed Head said:

One area that has caught some people is the EGR system.  Since your engine sounds good at idle you might try disabling it to see if anything changes.  I think it actuates by ported vacuum so blocking that hose might have an effect.

And like jr says above, make sure that the AFM vane is moving freely.  When I was watching your video I thought I saw it hang, its movement trailing the engine sound, but I couldn't be positive when i rewatched it.  A slight delay in vane reaction will lean things out and cause intake popping.  And as CO suggested, if the AFM has been messed with maybe the atlanticz calibration procedure is the way to go.  I'd get a magnifying glass and see if I could find the original glue blob traces myself.  Or crank that potentiometer up and try to drive it.

Something will show up.  You're doing all of the right things.

The EGR system has been removed and blocked off on the intake plenum. The AFM does move freely, I have never been able to get it to bind or feel any resistance in its movement.

Spark Test

Pulling injector connector test. (Apologizes for the shaky video at times, it is not easy handling all of these items at the same time.)

Reemphasizing the impact #6 injector connector has on idle speed.

FP/RPM/Vacuum Video:

 

Edited September 1, 2018 by kinser86
Forgot to add last video link.

[Zed Head]

49 minutes ago, kinser86 said:

It was incorrect, vacuum source was after throttle body. I put it below the throttle body per the FSM. Timing/Idle speed adjusted back to 10°BTDC @ 800RPM.

 

So after this, I am really perplexed with #2 and #3 injector having minimal impact on idle speed.In the video you can definitely see about a 100rpm drop on all other cylinders. I have not been able to reduce idle speed yet but I forgot my vacuum pump to test the FPR. 

The vacuum hose mistake would have led to the timing being retarded by the total amount of vacuum advance possible.  Probably about 14 degrees.  So when you opened the throttle timing would have dropped to about -4.  Of course as RPM increased centrifugal advance would bring it back up.  Retarded timing will reduce power by quite a bit.  The car might be drivable now, but still "poppy".

You can check if the advance hose is correct by removing it when measuring timing at idle.  Nothing should happen.  Then with the hose connected timing should advance as soon as you crack the throttle.

 

Weak cylinders won't show a big effect if you cut fuel by disabling the injectors.  Low compression or burned valves for example.  If you're sure the injectors are working that would be a good place to focus, assuming that you know you have spark.

Here's another thought from other people's past problems.  After these engines sit for a while the valves and guides get sticky and sometimes they spit a lash pad.  Then the vlave doens't open any more.  It usually happens at high RPM after people give the engine  a little road tuneup.  The way you were revving the engine in the first video it wouldn't be a surprise if that happened.  These engines are so smooth that sometimes it's hard to tell when a cylinder is not firing.  You might rerun your pressure check or recheck the valve lash.  Could also be that you didn't get a lock nut tight and lash has changed.

[Patcon]

I wouldn't think a burnt would be an issue since his compression numbers are so good. He could have one or more dead cylinders. The way it sounds in the earlier video that would be my first suspect. I am not sure those 2 injectors are fueling. Maybe they are plugged up with trash. What about doing a bench flow test on the injectors to make sure they all flow? EFI is not my forte...

[kinser86]

18 hours ago, Zed Head said:

The car might be drivable now, but still "poppy".

You can check if the advance hose is correct by removing it when measuring timing at idle.  Nothing should happen.  Then with the hose connected timing should advance as soon as you crack the throttle.

Weak cylinders won't show a big effect if you cut fuel by disabling the injectors.  Low compression or burned valves for example.  If you're sure the injectors are working that would be a good place to focus, assuming that you know you have spark.

Here's another thought from other people's past problems.  After these engines sit for a while the valves and guides get sticky and sometimes they spit a lash pad.  Then the vlave doens't open any more.  It usually happens at high RPM after people give the engine  a little road tuneup.  The way you were revving the engine in the first video it wouldn't be a surprise if that happened.  These engines are so smooth that sometimes it's hard to tell when a cylinder is not firing.  You might rerun your pressure check or recheck the valve lash.  Could also be that you didn't get a lock nut tight and lash has changed.

I did not try to drive it after #2 and #3 did not respond to injector connectors being pulled. I did check continuity to the ECU and dropping resistor for both connectors as a fail safe and they were both good. I can perform another leak down and compression test with a warm engine this time and also check the valve lash. If these numbers are good, then the only assumption would be the injector is truly not firing even though there is a clear audible clicking of the injector during idle. I marked the injectors prior to them being serviced so they went back to the cylinder they originally came from. One quick test would be to swap a known working to one of the #2 or #3 position and see if the issue follows the injector or stays with the cylinder.

12 hours ago, Patcon said:

I wouldn't think a burnt would be an issue since his compression numbers are so good. He could have one or more dead cylinders. The way it sounds in the earlier video that would be my first suspect. I am not sure those 2 injectors are fueling. Maybe they are plugged up with trash. What about doing a bench flow test on the injectors to make sure they all flow? EFI is not my forte...

Right now a visual inspection on those two injectors is a good idea. I think switching positions will help determine if its an injector or the cylinder.

Right now the priority list is:

1.  Determine why #2 and #3 injectors do not impact idle speed
   1. Warm Engine
      1. Compression test again
      2. Leak down test again
   2. Valve lash
      1. If out of spec, adjust and re-run compression and leak down
   3. Swap injectors with others on rail to see if idle speed follows injector or not
      1. If it follows injector, then bad injector
      2. If it stays at cylinder, something else is going on
2. Vacuum pump test the FPR (still on the list but need to get #2 and #3 on board)

I can't make any future decisions on next steps but if the numbers don't match up on #2 and #3 and injectors are good, then it sounds like the head needs to come off. As soon as I get those numbers I will post them up. I will take some videos and pictures again since they help so much. Thanks again for everyone's input, it is definitely helping! ?

[Zed Head]

Pulling the head seems drastic.  Maybe you meant valve cover?

You can fire/open the injectors while they're still on the rail.  Just ground them at the ECU connector with the key on.  Get six little cups, or small soda bottles and let them run for about 10-20 seconds, see how much comes out.  You'll know if one or two is clogged.  The screens in the inlets can get blocked easily.

My comments about valve problems were assuming that something happened after you did your first round of tests.  You never know.

[kinser86]

2 hours ago, Zed Head said:

Pulling the head seems drastic.  Maybe you meant valve cover?

You can fire/open the injectors while they're still on the rail.  Just ground them at the ECU connector with the key on.  Get six little cups, or small soda bottles and let them run for about 10-20 seconds, see how much comes out.  You'll know if one or two is clogged.  The screens in the inlets can get blocked easily.

My comments about valve problems were assuming that something happened after you did your first round of tests.  You never know.

I was thinking more on the lines if the compression/leak down test are no good on those cylinders. I will do some test first and let those numbers dictate the next step in the process.

[Patcon]

Swapping injectors around is a good diagnostic tool, but Zed Head's suggestion to just do a flow test with them on the rail might be a better way to do it