L28 Rough idle after head gasket. Need help.

[Jspec603]

Hi everyone,

 

I need to reach out to some of you long time Z owners for some assistance.  I recently did a head gasket job for a buddy on his 280z.  Ran into every possible issue I've read up on.  I spent a while drilling out and tapping studs, jumped a tooth on the timing either when I was inserting or removing my wooden wedge, etc etc.  Took it all down and reset the timing.

 

I now have this car all back together.  I checked my timing marks over and over, clock the distributor shaft to 11:25 (as close as it would come), verified with the screw driver trick between the bolt holes etc.  It is currently timed to 10* btdc on the crank pulley.

 

However, I am currently at a loss as to where to go next.  The car is fouling plugs like crazy.  Super erratic idle.  Blows black smoke (unburnt fuel, hence the fouling.) etc.  I've tried a second set of plugs, distributor and wires off my own 280z.  I've done a fuel pressure test while running, holds between 34-36 at idle(the needle is jumpy)  I've made sure to check connections at the temp sensors, AFM, injectors (wired new clips in already).  I've blown out the return line etc.  I've pretty much done everything I could find online for common causes of this symptom via google search.  However, that really didn't get me anywhere.  So here I am.

 

Below I'm going to post photos of my timing settings.  Also a few vid clips of the car running as well as the fuel pressure test.

 

Any and all help would be greatly appreciated! 

 

New Plugs 1-6 left to right.  Have had to pull and clean them numerous times.

 

Timing link on crank, is a little blurry...

 

Timing link at #1 spot on cam gear

 

Cam lobes

 

Cam notch

 

Distributor at TDC (don't have a photo of the tang)

 

 

Here are a few vids of it running and the fuel pressure while running;

 

Fuel pressure

http://s456.photobucket.com/user/jspec603/media/100_2832_zpscb17443c.mp4.html

 

Running with slight acceleration

http://s456.photobucket.com/user/jspec603/media/100_2834_zps2c507208.mp4.html

 

http://s456.photobucket.com/user/jspec603/media/100_2834_zps2c507208.mp4.html

 

 

Running at idle

http://s456.photobucket.com/user/jspec603/media/100_2831_zps53953a5e.mp4.html

 

http://s456.photobucket.com/user/jspec603/media/100_2830_zps66d90abe.mp4.html

 

 

 

I hope you guys can offer some good feedback and suggestions.

 

Sorry for a long post

 

Tom

Edited March 30, 2013 by Jspec603

[Xnke]

Check the coolant temperature sensors. This car is still fuel injected, right?

[NewZed]

As Xnke says, but check at the ECU connector.  Then you'll know what the ECU sees.  Compare the resistance reading to the temperature table in the FSM or the Fuel Injection book.

[Jspec603]

I'll double check the sensor.  I did have a friend helping me at one point and he did check it with a multi-meter and it was reading 2.1 ohms I believe.  but I'm not sure what the engine temp was at the time, so I can not honestly say if it was accurate.  However, I did not check this myself, so I will go back and do it again.  

 

I'll try it as the ECU as suggested as well.

 

Thanks for the input guys.

[seattlejester]

Did you replace the intake/exhaust gasket? A leaking gasket can make the car run pretty rich if everything else is the same.

Firing order 153624?

[Jspec603]

I did, yes.  He had bought the complete Felpro gasket kit.  I've even tried spraying brake/carb clean around the runners to see if I could get it to choke a little with no results.

 

And yes, that is what I have the firing order at, that alone has been checked numerous times.  I've also tried rotating the plugs clockwise an counter clockwise on the dizzy cap to see if the #1 was wrong.

[Jspec603]

Ok, so here are my findings as I'm going, am doing the tests as described in the FSM.

 

Thermotime sensor;

 

Continuity between sensor and block, none. Check

Pin #46 to swtich body, no resistance. Check

Pin #45 to swtich body, 51-62 ohms. Fail, no reading.

Resistance between pins #45 an #46 @ 60*. Fail, reads 4.28 ohms.  Book wants to see between 2.75 and 3.25.

Continuity between pin #13 @ ECU and body, none. Fail

 

I have not warmed the car up as of yet, need to clean up the plugs again so it'll fire.  But it makes sense at this point, the sensor is reading higher ohms so it's telling the ECU that it is actually colder which would make it want to dump more fuel.

 

With out warming the car up and testing the sensor further, I feel it's safe to rule this as the cause of the rich condition at this point.

 

 

Question on the water temp sensor and the thermo time sensor.  Are they the same part?  Most of the local stores list the sensor for the cluster and a 2 prong sensor for water temp.  I just wanna make sure before I get one for the car that it uses the same 2 pin sensor for both.

Edited March 29, 2013 by Jspec603

[NewZed]

You might have the thermotime and water temperature sensor connections reversed.  They're both EV1 style.  Try swapping them at the thermostat housing and recheck resistance at the ECU connector.  And/or measure resistance directly across the two pins on the water temp. sensor at the thermostat housing.  It's a tight squeeze but doable.

 

Measure resistance don't just do a go/no-go continuity test.  There's a table in the Engine Fuel chapter of resistance versus temperature.

[Jspec603]

Thanks for the input.  

 

If you re-read my last post, you'll see that I did reference the book and temperature table.  Unless I am misunderstanding your meaning.

 

As for having the plugs reversed, I don't feel this is the case.  I under stand that they are reverse-able and could easily be mixed up, one of the previous owners of the car had made the two pigtail leads longer and shorter to reach the specific sensor and taped them off.

 

There is a brown plug that goes to the water temp sensor w/ 6-7" of lead and a yellowish plug that goes to the thermo time sensor w 3-4" of lead.

 

I did however check the wrong pin at the ECU in my last post.  I checked pin #13, water temp sensor.

 

I just double checked the FSM, it should be pin #4 and #21.  Both have continuity to the body, but no resistance across the two pins at the ECU.

 

I still feel like getting a new sensor would be the appropriate way to go at this point.

 

Does anyone know if the two sensors are interchangeable? Water temp and thermo time?

 

Rock Auto has one 2 pin water temp sensor listed, not specifying if it is for thermo time or not.

[NewZed]

On a 280Z, pin 13 is one leg of the water temperature sensor circuit.  That's what I was talking about, you said no continuity.  That's the one you should be getting a resistance reading on.

 

Wires 45 and 46 are the thermotime switch and the CSV.  Yu should read ~60 ohms through the resistance of the heater in the thermotime switch when it's cold.  So 60* is a litle confusing there too, what does the * mean?  But it's not the water temp sensor anyway.

 

A 280Z ECU connector only has 35 pins.  Are you reporting the numbers shown in the FSM?  You can do most of what you need to know right at the 35 pin connector inthe car.  You might want to work from a wiring diagram like the one on page EF-28 in the 78 FSM, it will help.  Pin numbers to the ECU and parts labeled.

 

But, as far as the thermotime switch and the water temp. sensor, they're very different.  One's a sensor, one's a switch.

 

Sorry.  Sounds like you're almost to a solution.  Don't forget that block could eaily be 10 degrees colder than outside (if the 4.28 you reported is actually the sensor reading).

Edited March 30, 2013 by NewZed

[Jspec603]

Zed, sorry about the confusion.  The * is what I use when I am lazy and don't want to type out the word degree  .

 

What I was temping was the coolant with a thermometer as per the book  At the radiator cap it was reading 60 degrees.  That was my fault   as that is the test for the temp sensor, not the thermo time switch.  I was not checking the single leg sensor as I know that goes to the cluster only.

 

As for the pins I was referring to, per page 23 of the "engine fuel" section of my PDF, pins #4 and #21 on the ECU plug are tested to chassis ground for continuity.  I am not stopping there either   . Just wanted to preform each test per the book.

 

Pin #35 is listed as a ground circuit on the diagram.

 

I'm double checking the switch readings again just in case.  Directly at the switch I get no reading between the two posts, 45 & 46.  Also, at the ECU on pin #4 & #21, I get no reading.  Neither equate to  ~60 ohms as you stated.

 

I think it's fair to say the switch is inop.

Edited March 30, 2013 by Jspec603

[Dan_Austin]

Your fuel pressure looks high at idle.  Have you confirmed the manifold vacuum line is connected

to the regulator and that the pressure changes with engine speed/load?  I have to run out, so I cannot

check the FSM, but if I recall correctly, 36 PSI is correct, but at WOT/no vacuum/no boost.

 

Based on what I think you should be seeing for vacuum, I would expect reading between 22 and 26,

and since the relationship between flow and fuel pressure is not linear, the fact you have close to 50%

too much pressure would lead to between 5 and 15% too much fuel at idle.

[NewZed]

Dan might be on to something.  ~36 psi is the right number without the vacuum hose, ~26-28 with (in my experience) with the hose connected and engine idling.  If the vacuum hose is connected, check it for gasoline.  It should be dry.  Your FPR might be damaged.

 

By the way, your first post "videos" are just pictures.  On my computer.

[Jspec603]

Dan, I thought it was high as well.  But at this point, I feel it's an entirely different problem.  The thermo time switch is most definitely in-operational with zero resistance or continuity between the two posts on the switch.

 

I may pull the switch out of my own Z (already verified it reads properly) and just try it in this car to see if it corrects the issue.

 

Then I will move onto the next issue if there is success.

[Jspec603]

Zed, strange they were working links when I first made the thread.  I'll look into the fuel pressure after I try my switch.

 

I did however already try disconnecting the vacuum line for a few minutes while the car was running to see if it started spitting fuel or not.  The FPR was actually one of my first thoughts as to a suspect.  At this point it appears that this is a combined effort of failing parts. 

[NewZed]

The thermotime switch only runs the cold start valve.  Once the engine starts, it's useless.  Often people look at the CSV as a potential leak source for excess fuel but it's uncommon.  Worth a check though.

 

You're deep enough in to it that sitting down and reading the Engine Fuel chapter from page 1 would really help you out.  It will help focus your feelings.

 

Good luck.

[Jspec603]

Fixed the links to the videos.

 

Looked into a few more things.  First off, I checked the vacuum at the FPR.  It seemed weak so I removed the nipple fitting and found it was almost completely closed up with sludge.  Popped it in the bench vice (on the hex portion) and ran a drill bit through it, opened it back up nicely.  However, it did not help the issue.

 

I was however playing around with my hose pliers and was able to pinch off the feed line between the filter and pressure gauge.  Tried to get it as close to the 22ish psi that you all recommended and she ran pretty decent.  Below is a link to that video.

 

http://s456.photobucket.com/user/jspec603/media/100_2844_zpsde89ed5d.mp4.html

 

The more I starve it of fuel, the smoother the idle gets (to a point, then it dies).  It's idling high because I have the screw adjusted way out at the moment.  I did this because it was the only way I was able to keep some kind of idle.

 

 

Also, Zed, I am going to do just that.  You are correct on that matter for certain.  

Edited March 30, 2013 by Jspec603

[ISPKI]

Not sure if a 77 280z and a 78 280z are very different but the FSM states that fuel pressure should be around 36. From what I have read, this should increase when throttle is applied - my 77 280z idles around 34-36 and pops up to about 41 at WOT. From reading the FSM, the temperature sensor can cause many issues with how your vehicle runs if it is not functioning. I would start with replacing that (around 10$ at rockauto) and see how it does from there.

 

Also - Make sure that the vacuum line at the FPR nipple is the correct size and has no leaks. I replaced mine with a slightly larger diameter because I could not get the correct size on and the car would not run at all. I tried putting hose clamps on it as well, but it still would not run. My buddy managed to get the correct size vacuum line on with his tiny girl hands and the thing starts and runs fine.

Edited April 2, 2013 by ISPKI

[Pharaohabq]

if that FPR was all clogged up, you might also check the hose leading to it. It may be all clogged up too.   I was thinking your dizzy might be off still, since it's possible that the oil pump may be off a tooth,  if it is it could cause a lot of issues, though you said when you lowered the fuel pressure that it ran pretty decent, so maybe that's pretty far off the mark. Still, you might try adjusting +/- 5 deg on your dizzy and just see what it does before you start adusting the rest of the engine out of spec.

 

These cars are older than a lot of us, so there's not much chance of knowing what a previous owner may have done.  All your picts of the timing marks looked correct.

 

Let us know what you find if you get this sorted out.  How did swapping your thermotyme/temp sensor go?

[Jspec603]

Ok, so it's been a week since I last posted in here.  I had my buddy get a replacement thermo time switch and FPR, used but came off of a well running Z.  I verified the thermotime switch was good with my multimeter as well.  With these installed, it now seems to not want to run at all   .  I took the plugs back out and cleaned them up again and she barely runs now.

 

I decided to double check TDC just because.  I wanted to post pics of the distributor rotor direction and tang orientation.  Do you guys feel the tang is still off too much?  When I was installing the distributor drive shaft, this was as close as I could get it to the proper alignment.  One tooth over and it seemed to go well to the left, more like 9 o'clock if I had to guess.

 

Starting to get pretty discouraged here... 

 

To recap on what has been done to this point;

 

Replaced;

FRP
Thermotime

Plugs

swapped cap, rotor, wires from my own z

checked fuel pump

blew out return line

checked for vacuum leaks

checked fuel pressure

 

Here are the pics of rotor and tang orientation currently, at TDC

 

 

Edited April 11, 2013 by Jspec603