Nurdyguy

About a month ago, I noticed that the ol' girl was idling a little rough. I figured she just needed to warm up and it was no big deal. She seemed to be ok when I gave her some gas so I forgot about it.

Today I started her up and she idled a bit rough again, rougher than before. It was kind of a rumble-rumble-chug kind of sound (where rumble is the normal engine noise and chug is a rough spot). She sounded like she might stall on any one "chug" but never did. While driving to church, I at first thought she was fine with my foot on the gas, but then realized she was still "chugging" but it was just harder to hear because of the higher RPM.

She sat for two hours, and then we drove to In-n-Out. She seemed to get a little rougher as we went. We stopped at a red light and when I hit the gas (not hard, just normal acceleration from a stop) she sputtered a little but then moved like normal.

On the way home from In-n-Out it got a little worse. This time, starting when the light changed, she sputtered 2 or 3 times before getting going. Then when we got home and I was pulling into the driveway, I had to put her in reverse to straighten out. When I put her back into drive she stalled. I started her back up and as soon as I put her into drive she stalled again. She stalled a total of 4 times. The last time, I put a little extra gas as soon as I put her in drive and she was ok (still rough but didn't stall).

Any idea what's going on here?

Gun Jam

There are many things that could cause this...The only way to deal with something like this is to break down into categories then run basic test on each of those starting with the most simple and then moving on to the next before further investigation into any single category requires too much effort.

So we have

SPARK
FUEL
AIR
COMPRESSION
TIMING

Your issue is one of the above...pretty simple! But the trick now is coming up with simple test to isolate it to a single category..

You've provided a good staring description to start with if the issue occurred fairly quickly and got worse with in a few hours... Lets skip (COMPRESSION, TIMING) for now...we may revisit later

so we'll rearrange by most basic and work up.

AIR
FUEL
SPARK


So here are some basic test to run to help Isolate an issue I'll start with great ideas and work down.

AIR:
Take the air clearer off and try it...does the air cleaner look dirty?

Check for VAC leaks (highly suspect in you case) rotted hoses / missing hoses / disconnected hoses. carb cleaner sprayed around the carb base at idle will find its way into a vac leak and as its sucked in by the vacuum will cause engine idle to drop at the leak point...(its low risk but it is a fire hazard a fire extinguisher is recommended when ever dealing with fuel / running engines) ...Spray carb base and along intake and head seam.

FUEL:

Weak fuel pump: disconnect fuel line and place in glass jar have some one crank the engine over does it rapidly fill jar and attempt to splash out or it is pretty weak stream?

fuel filter....Locate and Replace

carb restriction could be a blockage in idle circuit can test by forcing choke closed a bit at a time if, as you close the choke it smooths out the idle and improves driveability then maybe think about cleaning carb out.

SPARK: pull boot off coil and place a metal object like a wrench 1" above coil post so that the other end of the wrench is touching bare metal (like intake or cylinder head)...crank the engine over does the spark jump from the coil to the wrench and pass through 1" of open air? It should. If not could be weak coil

Plug wire(s) could be issues with plug wires breaking down you could test with ohm meter

plugs: maybe fowled pull and check for carbon across electrode. look at plug color the ceramic part just behind the gap that is inside the combustion chamber should be brown and dry...the color of chocolate milk...not black, not bright white, not oily, not chunky black.

start with those test from the top down until you hit something suspect.

-Gun

Nurdyguy

Thanks Gun. It's a crazy week at work so I won't have a chance to try this out until the weekend. I'll post what I find.

Nurdyguy

I finally had some time to look at the car. The air filter does look pretty dirty and smells like gas. I also noticed that the hose from the air filter enclosure to the crankcase ventilator regulator valve was old and kinked. I'm honestly not quite sure what that would cause but then I looked closer at the regulator more closely it may well be original to the car... Old, crusty, oily, etc. That may not be the culprit but I'll replace it anyways.

Things I didn't mention before but should have:
1. I recently tried to clean out the engine compartment using some degreaser. This issue started before I did that but it got much worse after.
2. I've recently replaced both fuel filters (one in the pump and one on the carb).
3. I've also recently replaced all the plugs and wires.
4. I've recently replace the coil and ignition (converted to electronic).

Nurdyguy

Here is a quick video I took. It is tough to hear but it is there. The best example is at 10-sec right before it clicks to 11-sec.

Gun Jam

well it idles too well to be a vac problem (probably) but dont be shy about actually testing for it as described.

It sounds more like an ignition miss...So I would start with those test as described above. In addition you need to pull the cap off the dizzy now and check the rotor and components for water. Is it still points? IF water made thing worse thats a good indication of an ignition issue.

Nurdyguy

I replaced the ignition and coil with the Pertronix kit about a year ago. I'll check for water in the dist as you said (I put a bag over the dist when I was doing the cleaning but who knows where water may have gotten). I also installed an ignition kill switch a while back so I'll check to make sure the wires aren't loose or something silly like that.

Gun Jam

yeah its probably the petronix going bad...check for spark strength from the coil...with the boot off it should jump 1" of air no problem to a proper ground...If you cant get it to do that or it does it only a few times then not so much...investigate that for sure.

I had a few mds parts go bad a one of the old non digital a6 boxes and a coil. It would run great when cool but once they warmed up it would get flaky and do odd stuff ignition wise.

Nurdyguy

I started pull out plug wires and plugs to see if those were all in good shape (starting with simple things and working up to more complex) and one of the wires came out missing the plug clip (it was still on the plug). Looks like it was a bad crimp. I ordered some better plug wires, hope that was the only issue.

Gun Jam

Could be!

Let us know how it goes