Engine rough running - at wits end

[Zed Head]

I was looking at what appears to be the factory 1977 FSM.  Published in 1976.  But it's from the internet so who knows.  All good, .038 will run fine.

[JSM]

Did you check that each injector was firing? Wiring only. If you don't have a noid light I just used an old injector laying around that I had and you can actually check by turning the engine over without running it.

Did this car sit a long time? 

Also when the engine was at TDC did you check to see if the rotor was pointing at cyl 1 in the distributor?

Edited March 3, 2017 by JSM

[gundee]

3 hours ago, the_tool_man said:

Tonight I pulled the plugs, cleaned them and gapped them to .038". I pulled the valve cover and checked the valve lash. All were in spec. While I had it open, I rotated it to put #1 at TDC and verified the cam timing was correct. I checked the torque on the head bolts. They were all tight.

 

That is really a clean looking top end. Looks like the oil changes were very regular. The internals must be in excellent condition as well.

[the_tool_man]

I didn't know noid lights existed. I'll pick up a set. I didn't check the distributor. But I've already set the static timing. Would it run with the distributor 180 degrees off?

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[Dave WM]

you can load test by reving the engine if it will run better above idle, run the AC and lights to load it down some.

Changing too many things can lead to issues, before replacing all the injector wires see if you can hear them ticking. FYI when I was replacing the injector boots (yes just the boots, the plastic parts were fine), I ended up with a ruff idle. I was doing ONE injector boot at a time, would start the car and make sure all was good. well on #3 I must have not fully inserted the metal socket back into the boot cause all of a sudden I developed a miss. Easy to find since I had just done one thing so all I had to do was check that. Lesson being unless you are real good at diagnostics its best to only change one thing then like the eye doctor says "better or worse".

I am still thinking you have some clogged or non functioning fuel injectors (wiring or injector, maybe even ECU if you have the leads swapped around) from what you described in the prior load test, I would try to confirm that before doing too much more.

The problem with the noid light test is it will only confirm a pulse of electricity to the injector ( a good thing but not definite proof of a working injector) hearing it tick will confirm the pulse and a reaction from the injector, still not definite since there is no way to know its not plugged up. the only way to know for sure is to test them out of the manifold under fuel pressure with a pulse so you can see the spray pattern. This is quite a bit of work and is why I think the load test is important as you only want to do this if you are SURE that its isolated to one or more but not all the injectors. If all the injectors were not properly metering fuel I would look to pressure, signal, duty cycle (AFM/ECU).

Don't forget the CSV I don't recall you saying it was checked that is easy, pull the two bolts out (don't drop them in the manifold) pull the CSV up and look at it, is it leaking at all while the car in running, it should ONLY fire when the key is in the start position and then ONLY if the engine is cold, like less that 70f.

The remove the oil cap test is a good one as well, a well running engine will stumble and die at idle that is assuming the emission stuff is hooked up.

 

[the_tool_man]

I tried pulling the dip stick, removing the oil cap and pulling the vacuum line to the booster (at different times). The idle didn't change. This supports the vacuum leak theory. I'll spend more time on it this weekend with a stethoscope and a noid light to investigate the injectors.
I think I'm getting close.

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[JSM]

2 hours ago, the_tool_man said:

I tried pulling the dip stick, removing the oil cap and pulling the vacuum line to the booster (at different times). The idle didn't change. This supports the vacuum leak theory. I'll spend more time on it this weekend with a stethoscope and a noid light to investigate the injectors.
I think I'm getting close.

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Not sure if you have Autozone up there, but you can rent and return the noid light testing kit for free with a deposit. I think the other parts store do as well.

[Dave WM]

3 hours ago, the_tool_man said:

I tried pulling the dip stick, removing the oil cap and pulling the vacuum line to the booster (at different times). The idle didn't change. This supports the vacuum leak theory. I'll spend more time on it this weekend with a stethoscope and a noid light to investigate the injectors.
I think I'm getting close.

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An air leak so bad that it would not be effected by removing the oil filler cap should be noisey as heck.

[Zed Head]

3 hours ago, the_tool_man said:

I tried pulling the dip stick, removing the oil cap and pulling the vacuum line to the booster (at different times). The idle didn't change. This supports the vacuum leak theory. I'll spend more time on it this weekend with a stethoscope and a noid light to investigate the injectors.
I think I'm getting close.

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It might also indicate a clogged PCV valve.  That's where the extra air gets in when you remove the filler cap.  The booster hose though, that's a surprise since that would be a huge amount of extra unmetered air.  Should have seen an effect there. Odd.  Did you remove it at the manifold or at the booster?

You might also have extra fuel being supplied, since it didn't lean out and die.  Once you fix the leaks, if that's the problem, it will be running rich.  Your AFM might have been messed with.  You likely have a much longer path ahead of you, since you're learning in the fly.  Wait 'til we start talking about the BCDD.

The one thing that's confirmed though is that your system is way out of whack.  On a properly working EFI system, you can get an idle speed increase just from removing the tiny hose at the manifold that feeds the AC control bottle.  And removing the filler cap will kill the engine.

[siteunseen]

You have probably done this but I can't remember reading where you have or not but an unlit propane torch is is another easy and clean way for finding vacuum leaks.  

Have you looked above the thermostat housing to see if the valve cover gasket isn't upside down?  

 

[the_tool_man]

40 minutes ago, siteunseen said:

You have probably done this but I can't remember reading where you have or not but an unlit propane torch is is another easy and clean way for finding vacuum leaks.  

Have you looked above the thermostat housing to see if the valve cover gasket isn't upside down?  

 

I'm not comfortable with the propane torch method, especially right over the exhaust manifold.  I didn't think about the gasket being upside down.  It lined up with all the contours of the head, so I don't really see how it could be.  The gasket is visible in the photo I took of the valve train.  Can you tell?

[the_tool_man]

2 hours ago, Zed Head said:

It might also indicate a clogged PCV valve.  That's where the extra air gets in when you remove the filler cap.  The booster hose though, that's a surprise since that would be a huge amount of extra unmetered air.  Should have seen an effect there. Odd.  Did you remove it at the manifold or at the booster?

I disconnected it at the booster side of the check valve.  In fact, that's where I later measured the idle vacuum from.  Whether open or hooked up to my vacuum gauge, the engine behavior didn't change.