Engine rough running - at wits end

[siteunseen]

6 hours ago, the_tool_man said:

I didn't have much time to work on the car tonight. But I had a few minutes to poke around. The EGR/BPT recall has been done on my car (see photo of sticker). I used a mirror and looked under the intake. I didn't see any holes; not even any surface corrosion.

I picked up a remote starting switch, too. It'll come in handy for compression testing.
 

That's good news and will save you a lot of time plus now I know what that sticker says, I've never seen one before.

The remote starter, 17mm and 14mm open end wrenches, and for one lock nut on mine I have to use a 17mm crow's foot socket, feeler gauges and you're set for a valve adjustment.

Looky what I found!

 

[the_tool_man]

Keep in mind that does not guarantee that the EGR valve is not stuck.

True. I plan to make a block off plate to eliminate that as a cause.

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[sweatybetty]

im going to toss out an idea. i wonder id maybe the tailpipe/muffler is plugged

[the_tool_man]

Quick update. I used the vacuum line from the brake booster to check idle vacuum. It's below 5" at idle. So I have a big vacuum leak. I've checked all of the hoses for obvious leaks. So I decided that before I start replacing all that mess, I'd pull the EGR valve. It was a welcome relief to break the nuts loose without breaking off the studs. A first, I think! My EGR has a thick cast spacer, necessitating long studs. They're stuck, of course. I plan to pick up a new EGR gasket and make a block-off plate.

If this isn't it, I'll just replace all of the vacuum hoses and go from there.

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[siteunseen]

If you decide to remove all that stuff I can post up some pictures of mine.  Instead of buying an early intake I did my n-47 like you have.  Glad to do that if you need something.  

[the_tool_man]

4 hours ago, siteunseen said:

If you decide to remove all that stuff I can post up some pictures of mine.  Instead of buying an early intake I did my n-47 like you have.  Glad to do that if you need something.  

I'm giving serious consideration to stripping down the entire intake and getting rid of all the emissions junk, if for no other reason than to eliminate a bunch of potential problems.  But that's for another thread.

[Captain Obvious]

Did you check the PCV hose on the underside of the intake manifold? If you've never seen it, you might not even know it's there.

[Zed Head]

7 hours ago, the_tool_man said:

Quick update. I used the vacuum line from the brake booster to check idle vacuum. It's below 5" at idle. So I have a big vacuum leak. I've checked all of the hoses for obvious leaks. So I decided that before I start replacing all that mess, I'd pull the EGR valve. It was a welcome relief to break the nuts loose without breaking off the studs. A first, I think! My EGR has a thick cast spacer, necessitating long studs. They're stuck, of course. I plan to pick up a new EGR gasket and make a block-off plate.

Manifold vacuum has little to do with determining if you have a vacuum leak.  What it measures is how well, and how, the engine is pulling air.  You might have a vacuum leak but that's not what the vacuum gauge is used for.  And you'd be better off to block the brake booster line and use a small port on the manifold for the gauge.  Plus, when you give a vacuum gauge reading you should also include RPM.

Might be worthwhile to reset and re-describe what the problem is.  You've probably changed some things, and verified others, and have more numbers to report, since the last post almost three weeks ago.  And you might be better at describing what's going on.  We're on Page 2 now and I don't remember what the issue is beside rough-running.  It almost always helps to review work done.

[gundee]

Before doing anything else. Pull the valve cover and post a photo. If anything is amiss there, someone here will spot it for you.

[the_tool_man]

12 hours ago, Zed Head said:

Manifold vacuum has little to do with determining if you have a vacuum leak.  What it measures is how well, and how, the engine is pulling air.  You might have a vacuum leak but that's not what the vacuum gauge is used for.  And you'd be better off to block the brake booster line and use a small port on the manifold for the gauge.  Plus, when you give a vacuum gauge reading you should also include RPM.

Might be worthwhile to reset and re-describe what the problem is.  You've probably changed some things, and verified others, and have more numbers to report, since the last post almost three weeks ago.  And you might be better at describing what's going on.  We're on Page 2 now and I don't remember what the issue is beside rough-running.  It almost always helps to review work done.

My methodology at this point is to take the list of possible causes provided by the contributors to this thread, and eliminate them, starting with easiest first.

Vacuum leaks seem to be most likely, and with the exception of an intake manifold gasket leak, would seem to be easiest to check.  Then I'll test the CSV.  Next is a compression test.  Then valve lash, timing chain, etc.

I chose measuring vacuum at the booster line specifically to isolate possible diaphragm failure.  I also tested the check valve while I was there (it's working).  Engine RPM was at idle.  But I couldn't see the tach while I was doing it.  I'd guess 750 RPM.  When I revved it, vacuum increased as expected.  But I didn't attempt to correlate vacuum with RPM.

I didn't mention it because it didn't seem important.  But the EGR valve is really dirty.  The pintle moves freely under finger pressure.  But I can't tell if it seals when closed.  I can't really test it until I have a block-off plate made to cover the openings in the intake.  Then I can hook it up and visually test it if I want to.  If the pintle moves with vacuum, I could attempt to clean it.  But the plate will eliminate it as a cause for now.

I don't have anything else to report.  Between work, family and other obligations (including the death of a friend), I've only had about 30 minutes with the car in the last several weeks.  I should get more testing done this week.  Plans today include borrowing a stud extractor from a friend, picking up an EGR valve gasket.  If time allows this evening, I'll make a block-off plate.

Edited February 27, 2017 by the_tool_man

[Dave WM]

compression check should be one of the 1st things to check. A load test by disabling one cylinder at a time is quick and easy too. May point to a problem isolated to just one cylinder.

[JSM]

2 hours ago, the_tool_man said:

I don't have anything else to report.  Between work, family and other obligations (including the death of a friend), I've only had about 30 minutes with the car in the last several weeks.  I should get more testing done this week.  Plans today include borrowing a stud extractor from a friend, picking up an EGR valve gasket.  If time allows this evening, I'll make a block-off plate.

Sorry to hear about your friend.  Yeah cars come second, third, fourth...